| 1. |
- Awasthi, Mukesh Kumar, et al.
(author)
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Filamentous fungi for sustainable vegan food production systems within a circular economy : Present status and future prospects
- 2023
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In: Food Research International. - : Elsevier BV. - 0963-9969 .- 1873-7145. ; 164
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Journal article (peer-reviewed)abstract
- Filamentous fungi serve as potential candidates in the production of different value-added products. In the context of food, there are several advantages of using filamentous fungi for food. Among the main advantages is that the fungal biomass used food not only meets basic nutritional requirements but that it is also rich in protein, low in fat, and free of cholesterol. This speaks to the potential of filamentous fungi in the production of food that can substitute animal-derived protein sources such as meat. Moreover, life-cycle analyses and techno-economic analyses reveal that fungal proteins perform better than animal-derived proteins in terms of land use efficiency as well as global warming. The present article provides an overview of the potential of filamentous fungi as a source of food and food supplements. The commercialization potential as well as social, legal and safety issues of fungi-based food products are discussed.
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| 2. |
- Chandolias, Konstantinos, 1985-, et al.
(author)
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Bio‑hydrogen and VFA production from steel mill gases using pure and mixed bacterial cultures
- 2023
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In: Bioresource Technology Reports. - : Elsevier Ltd. - 2589-014X. ; 23
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Journal article (peer-reviewed)abstract
- A major source of CO2 emissions is the flaring of steel mill gas. This work demonstrated the enrichment of carboxydotrophic bacteria for converting steel mill gas into volatile fatty acids and H2, via gas fermentation. Several combinations of pure and mixed anaerobic cultures were used as inoculum in 0.5-L reactors, operated at 30 and 60 °C. The process was then scaled up in a 4-L membrane bioreactor, operated for 20 days, at 48 °C. The results showed that the enriched microbiomes can oxidize CO completely to produce H2/H+ which is subsequently used to fix the CO2. At 30 °C, a mixture of acetate, isobutyrate and propionate was obtained while H2 and acetate were the main products at 60 °C. The highest CO conversion and H2 production rate observed in the membrane bioreactor were 29 and 28 mL/LR/h, respectively. The taxonomic diversity of the bacterial community increased and the dominant species was Pseudomonas.
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| 3. |
- Chandolias, Konstantinos, 1985-, et al.
(author)
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Effects of Heavy Metals and pH on the Conversion of Biomass to Hydrogen via Syngas Fermentation
- 2018
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In: BioResources. - : BioResources. - 1930-2126. ; 13:2, s. 4455-4469
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Journal article (peer-reviewed)abstract
- The effects of three heavy metals on hydrogen production via syngas fermentation were investigated within a metal concentration range of 0 to 1.5 mg Cu/L, 0 to 9 mg Zn/L, 0 to 42 mg Mn/L, in media with initial pH of 5, 6, and 7, at 55 degrees C. The results showed that at lower metal concentration, pH 6 was optimum while at higher metal concentrations, pH 5 stimulated the process. More specifically, the highest hydrogen production activity recorded was 155% +/- 12% at a metal concentration of 0.04 mg Cu/L, 0.25 mg Zn/L, and 1.06 mg Mn/L and an initial medium pH of 6. At higher metal concentration (0.625 mg Cu/L, 3.75 mg Zn/L, and 17.5 mg Mn/L), only pH 5 was stimulating for the cells. The results showed that the addition of heavy metals, contained in gasification-derived ash, can improve the production rate and yield of fermentative hydrogen. This could lead to lower costs in gasification process and fermentative hydrogen production and less demand for syngas cleaning before syngas fermentation.
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| 4. |
- Harirchi, Sharareh, et al.
(author)
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Microbiological insights into anaerobic digestion for biogas, hydrogen or volatile fatty acids (VFAs) : a review
- 2022
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In: Bioengineered. - : Taylor and Francis Ltd.. - 2165-5979 .- 2165-5987. ; 13:3, s. 6521-6557
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Journal article (peer-reviewed)abstract
- In the past decades, considerable attention has been directed toward anaerobic digestion (AD), which is an effective biological process for converting diverse organic wastes into biogas, volatile fatty acids (VFAs), biohydrogen, etc. The microbial bioprocessing takes part during AD is of substantial significance, and one of the crucial approaches for the deep and adequate understanding and manipulating it toward different products is process microbiology. Due to highly complexity of AD microbiome, it is critically important to study the involved microorganisms in AD. In recent years, in addition to traditional methods, novel molecular techniques and meta-omics approaches have been developed which provide accurate details about microbial communities involved AD. Better understanding of process microbiomes could guide us in identifying and controlling various factors in both improving the AD process and diverting metabolic pathway toward production of selective bio-products. This review covers various platforms of AD process that results in different final products from microbiological point of view. The review also highlights distinctive interactions occurring among microbial communities. Furthermore, assessment of these communities existing in the anaerobic digesters is discussed to provide more insights into their structure, dynamics, and metabolic pathways. Moreover, the important factors affecting microbial communities in each platform of AD are highlighted. Finally, the review provides some recent applications of AD for the production of novel bio-products and deals with challenges and future perspectives of AD. © 2022 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
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| 5. |
- Jomnonkhaow, Umarin, et al.
(author)
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Membrane bioreactor-assisted volatile fatty acids production and in situ recovery from cow manure
- 2021
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In: Bioresource Technology. - : Elsevier. - 0960-8524 .- 1873-2976. ; 321
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Journal article (peer-reviewed)abstract
- Cow manure (CM) generation in large volumes has for long been considered a waste management challenge. However, the organic content of CM signals opportunities for the production of value-added bioproducts such as volatile fatty acids (VFAs) through anaerobic digestion (AD). However, a robust VFAs fermentation process requires effective methane formation inhibition and enhance VFAs recovery. In this study, thermal pretreatment was applied to inhibit methanogens for enhanced VFAs production and an immersed membrane bioreactor (iMBR) for in situ recovery of VFAs in a semi-continuous AD. Maximal VFAs yield of 0.41 g VFAs/g volatile solids (VS) was obtained from thermally-treated CM without inoculum addition. The CM was further fed to the iMBR operating at organic loading rates of 0.8–4.7 gVS/L.d. The VFAs concentration increased to 6.93 g/L by rising substrate loading to 4.7 g VS/L.d. The applied iMBR set-up was successfully used for stable long-term (114 days) VFAs production and recovery.
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| 6. |
- Mukesh Kumar, Awasthi, et al.
(author)
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A critical review of organic manure biorefinery models toward sustainable circular bioeconomy: Technological challenges, advancements, innovations, and future perspectives
- 2019
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In: Renewable & sustainable energy reviews. - : Elsevier BV. - 1364-0321 .- 1879-0690. ; , s. 115-131
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Journal article (peer-reviewed)abstract
- Total livestock emissions account for up to 14.5% of man-made greenhouse gas emissions. Counteractive measures, such as circular economy concepts and negative emission technologies are necessary to limit global warming below 1.5 °C. Possible treatment options for organic manure include anaerobic digestion, combustion, gasification, hydrothermal liquefaction and composting. The choice of treatment varies depending on the economics, the requirement of a specific product, and sociocultural factors. Commercialization of these treatments needs a blend of appropriate technology, feasible economics, policy support and agreeable socio-cultural conditions. Key findings of this study include the following: 1. Increasing scientific awareness about manure management and treatment; 2. Building a sustainable cooperative model to commercialize technologies; 3. Creating a market for manure recycling products; 4. The role of policy in supporting technologies and consumers; and 5. The codigestion of substrates for better efficacy. Current trends show minimal actions in place as opposed to the high-rate of acceleration that is necessary.
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| 7. |
- Mukesh Kumar, Awasthi, et al.
(author)
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Metagenomics for taxonomy profiling : tools and approaches
- 2020
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In: Bioengineered. - : Taylor & Francis. - 2165-5979 .- 2165-5987. ; 11:1, s. 356-374
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Journal article (peer-reviewed)abstract
- The study of metagenomics is an emerging field that identifies the total genetic materials in an organism along with the set of all genetic materials like deoxyribonucleic acid and ribose nucleic acid, which play a key role with the maintenance of cellular functions. The best part of this technology is that it gives more flexibility to environmental microbiologists to instantly pioneer the immense genetic variability of microbial communities. However, it is intensively complex to identify the suitable sequencing measures of any specific gene that can exclusively indicate the involvement of microbial metagenomes and be able to advance valuable results about these communities. This review provides an overview of the metagenomic advancement that has been advantageous for aggregation of more knowledge about speci?c genes, microbial communities and its metabolic pathways. More speci?c drawbacks of metagenomes technology mainly depend on sequence-based analysis. Therefore, this ‘targeted based metagenomics’ approach will give comprehensive knowledge about the ecological, evolutionary and functional sequence of significantly important genes that naturally exist in living beings either human, animal and microorganisms from distinctive ecosystems.
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| 8. |
- Mukesh Kumar, Awasthi, et al.
(author)
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Methanogen and nitrifying genes dynamics in immersed membrane bioreactors during anaerobic co-digestion of different organic loading rates food waste
- 2021
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In: Bioresource Technology. - : Elsevier. - 0960-8524 .- 1873-2976. ; 342
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Journal article (peer-reviewed)abstract
- This work was aimed to evaluate the distinctive food waste (FW) organic loading rates (OLR) on methanogen and nitrifying genes dynamics and its correlation with identified relative abundance of bacterial dynamics during the anaerobic digestion. This experiment were carried out in the digesters at high OLR of food wastes at (4 to 8 g volatile solids/liter/day reactor R1) and (6 to 10 g volatile solids/liter/day reactor R2). The results shown that the relative abundance of mcrA, mcrB and mcrG genes were richest in the first day of both R1 and R2. In addition, the most of nitrifying genes were greater in after 34 days digestion in R2, while these genes did not show the specific regularity in R1. Finally, the correlation figure shows that Clostridium and Lactobacillus genera were significantly correlated with the different organic acids and methanogen and nitrifying genes dynamics.
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| 9. |
- Mukesh Kumar, Awasthi, et al.
(author)
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Techno-economics and life-cycle assessment of biological and thermochemical treatment of bio-waste
- 2021
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In: Renewable & sustainable energy reviews. - : Elsevier BV. - 1364-0321 .- 1879-0690. ; 144
-
Journal article (peer-reviewed)abstract
- The energy sector contributed to three-fourth of overall global emissions in the past decade. Biological wastes can be converted to useful energy and other byproducts via biological or thermo-chemical routes. However, issues such as techno-economic feasibility and lack of understanding on the overall lifecycle of a product have hindered commercialization. It is needed to recognize these inter-disciplinary factors. This review attempts to critically evaluate the role of technology, economics and lifecycle assessment of bio-waste in two processing types. This includes: 1. biological and, 2. thermo-chemical route. The key findings of this work are: 1. Policy support is essential for commercialization of a waste treatment technology; 2. adequate emphasis is necessary on the social dimensions in creating awareness; and 3. from a product development perspective, research should focus on industrial needs. The choice of the treatment and their commercialization depends on the regional demand of a product, policy support, and technology maturity. Utilization of bio-wastes to produce value-added products will enhance circular economy, which in turn improves sustainability.
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| 10. |
- Parchami, Mohsen, et al.
(author)
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MBR-Assisted VFAs production from excess sewage sludge and food waste slurry for sustainable wastewater treatment
- 2020
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In: Applied Sciences. - : MDPI AG. - 2076-3417. ; 10:8
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Journal article (peer-reviewed)abstract
- The significant amount of excess sewage sludge (ESS) generated on a daily basis by wastewater treatment plants (WWTPs) is mainly subjected to biogas production, as for other organic waste streams such as food waste slurry (FWS). However, these organic wastes can be further valorized by production of volatile fatty acids (VFAs) that have various applications such as the application as an external carbon source for the denitrification stage at a WWTP. In this study, an immersed membrane bioreactor set-up was proposed for the stable production and in situ recovery of clarified VFAs from ESS and FWS. The VFAs yields from ESS and FWS reached 0.38 and 0.34 gVFA/gVSadded, respectively, during a three-month operation period without pH control. The average flux during the stable VFAs production phase with the ESS was 5.53 L/m2/h while 16.18 L/m2/h was attained with FWS. Moreover, minimal flux deterioration was observed even during operation at maximum suspended solids concentration of 32 g/L, implying that the membrane bioreactors could potentially guarantee the required volumetric productivities. In addition, the techno-economic assessment of retrofitting the membrane-assisted VFAs production process in an actual WWTP estimated savings of up to 140 €/h for replacing 300 kg/h of methanol with VFAs. © 2020 by the authors.
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| 11. |
- Pinheiro, V. E., et al.
(author)
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Anaerobic digestion of cornmeal : the effect of crude enzyme extract and co-digestion with cow manure
- 2021
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In: Biofuels, Bioproducts and Biorefining. - : John Wiley and Sons Ltd. - 1932-104X .- 1932-1031.
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Journal article (peer-reviewed)abstract
- This study examined the effect of a crude enzyme extract, containing mainly starch-degrading enzymes, on cornmeal (Zea mays) hydrolysis. This was followed by an investigation of the effect of enzymatic treatment for the anaerobic digestion of this biomass. Cornmeal and cow manure were also co-digested, and both batch and semi-continuous experiments were performed. The enzymatic pretreatment of cornmeal resulted in a yield of 65 ± 5% reducing sugars, with 1:10 w/v (grams of dry substrate per mililiters of enzyme extract) enzyme load at 45 °C for 48 h. There was an 8% enhancement of methane production observed during the batch assays, both when cornmeal hydrolysate was digested and when enzymes were added directly to the digester. Synergetic effects were found when co-digesting cornmeal and cow manure, leading to higher methane yield (280 NmL gVS–1) than that (200 NmL gVS–1) calculated based on the methane potential of the individual substrates. Regarding long-term effects, the laboratory-scale semi-continuous experiments also demonstrated that the co-digestion of cornmeal and cow manure (1:1 volatile solid (VS) basis) led to a stable process reaching an organic loading rate of 3 g VS L day–1 and achieving a daily methane production of 1280.12 ± 99.4 NmL CH4/day. However, when cornmeal was investigated in mono-digestion, and the enzyme extract was directly added during semi-continuous digestion of cornmeal, volatile fatty acid (VFA) accumulation was observed, leading to a decrease in pH, and no significant enhancement of the conversion into methane was observed. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd
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| 12. |
- Qin, S., et al.
(author)
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Fungal dynamics during anaerobic digestion of sewage sludge combined with food waste at high organic loading rates in immersed membrane bioreactors
- 2021
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In: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 335
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Journal article (peer-reviewed)abstract
- In this study, the influence of distinct hydraulic retention times (HRT) and organic loading rates (OLRs) on fungal dynamics during food waste anaerobic digestion in immersed membrane-based bio-reactors (iMBR) were investigated. The organic loading rate 4–8 g VS/L/d (R1) and 6–10 g VS/L/d (R2) were set in two iMBR. T1 (1d), T2 (15d) and T3 (34d) samples collected from each bioreactor were analyzed fungal community by using 18s rDNA. In R2, T2 had the most abundant Ascomycota, Basidiomycota, Chytridiomycota and Mucoromycota. As for R1, T3 also had the richest Cryptomycota except above four kinds of fungi. Subsequently, the Principal Component Analysis (PCA) and Non-Metric Multi-Dimensional Scaling (NMDS) indicated that fungal diversity was varied among the all three phases (T1, T2, and T3) and each treatment (R1 and R2). Finally, the results showed that different OLRs and HRT have significantly influenced the fungal community.
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| 13. |
- Qin, S., et al.
(author)
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Microbial dynamics during anaerobic digestion of sewage sludge combined with food waste at high organic loading rates in immersed membrane bioreactors
- 2021
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In: Fuel. - : Elsevier. - 0016-2361 .- 1873-7153. ; 303
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Journal article (peer-reviewed)abstract
- This study was designed to evaluate the microbial profiling of anaerobic digestion during the processing of sewage sludge and food waste to volatile fatty acids (VFAs) in an immersed membrane bioreactor (iMBR) operating with a distinct organic loading rate (OLR). The results indicated that Firmicutes (0.17–0.38) and Actinobacteria (0.20–0.32) phyla dominated in anaerobic digestion with OLRs of 4 and 8 g VS/L/d, while Firmicutes (0.04–0.08), Actinobacteria (0.03–0.08) and Proteobacteria (0.02) were more abundant with OLR of 6 and 10 g VS/L/d in the bioreactors. Subsequently, the abundance of the Clostridium and Lactobacillus genera were responsible for higher yields of acetate, butyrate, caproate and lactate. The species of Clostridium sp. W14A (0.04–0.06), Bacterium OL-1(0.01–0.30) and Lactobacillus mucosae (0.002–0.01) were rich for both OLR dosages. Additionally, network and redundancy analysis confirmed that Clostridium sp. W14A, Bacterium MS4 and Lactobacillus had significant correlations with the VFAs produced, such as acetate, butyrate, and caproate. Variation analysis also demonstrated an appreciable correlation between environmental factors and the bacterial community. Overall, this bacterial community was dominated by the Firmicutes (0.04–0.38) phylum and Clostridium sp. W14A (0.04–0.60) species, which is a clear indicator of a lower population of acetogenic bacteria associated with greater VFAs generation.
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| 14. |
- Rousta, Neda, et al.
(author)
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Filamentous Fungus Aspergillus oryzae for Food : From Submerged Cultivation to Fungal Burgers and Their Sensory Evaluation – A Pilot Study
- 2021
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In: Foods. - : MDPI AG. - 2304-8158. ; 10:11
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Journal article (peer-reviewed)abstract
- New food sources are explored to provide food security in sustainable ways. The submerged fermentation of edible filamentous fungi is a promising strategy to provide nutritious and affordable food that is expected to have a low environmental impact. The aim of the current study was to assess the novel use of Aspergillus oryzae cultivated in submerged fermentation on oat flour as a source for food products that do not undergo secondary fermentation or significant downstream processing. The fungus was cultivated in a pilot-scale airlift bioreactor, and the biomass concentration and protein content of the biomass were assessed. A tasting with an untrained panel assessed consumer preferences regarding the taste and texture of minimally processed vegetarian and vegan burger patties made from the biomass, and how the patties fared against established meat-alternative-based patties. The cultivation of Aspergillus oryzae resulted in a yield of 6 g/L dry biomass with a protein content of 37% on a dry weight basis. The taste and texture of the minimally processed fungal burger patties were to the liking of some participants. This was also reflected in diverse feedback provided by the participants. The cultivation of the fungus on oat flour and its utilization in developing burger patties shows its promising potential for the production of nutritious food. The applications of the fungus can be further developed by exploring other favorable ways to texture and season this relatively new functional food source to the preferences of consumers.
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| 15. |
- Uwineza, Clarisse, et al.
(author)
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Cultivation of edible filamentous fungus Aspergillus oryzae on volatile fatty acids derived from anaerobic digestion of food waste and cow manure
- 2021
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In: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 337
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Journal article (peer-reviewed)abstract
- In a circular economy approach, edible filamentous fungi (single cell protein) can be cultivated on volatile fatty acids (VFAs) derived from anaerobic digestion (AD) of organic-rich waste streams. In this study, the effect of pH, concentration/distribution of VFAs, nutrient supplementation, and type of waste on Aspergillus oryzae cultivation on synthetic VFAs, and actual VFAs derived from AD of food waste and cow manure were investigated. The optimal pH for A. oryzae growth on VFAs were 6 and 7 with maximum acetic acid consumption rates of 0.09 g/L. h. The fungus could thrive on high concentrations of acetic (up to 9 g/L) yielding 0.29 g dry biomass/gVFAs(fed). In mixed VFAs cultures, A. oryzae primarily consumed caproic and acetic acids reaching a biomass yield of 0.26 g dry biomass/gVFAs(fed) (containing up to 41% protein). For waste-derived VFAs at pH 6, the fungus successfully consumed 81-100% of caproic, acetic, and butyric acids.
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| 16. |
- Vu, Hoang Danh, et al.
(author)
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Production of polyhydroxyalkanoates (PHAs) by Bacillus megaterium using food waste acidogenic fermentation-derived volatile fatty acids
- 2021
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In: Bioengineered. - : Taylor & Francis Group. - 2165-5979 .- 2165-5987. ; 12:1, s. 2480-2498
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Journal article (peer-reviewed)abstract
- High production costs still hamper fast expansion of commercial production of polyhydroxyalkanoates (PHAs). This problem is greatly related to the cultivation medium which accounts for up to 50% of the whole process costs. The aim of this research work was to evaluate the potential of using volatile fatty acids (VFAs), derived from acidogenic fermentation of food waste, as inexpensive carbon sources for the production of PHAs through bacterial cultivation. Bacillus megaterium could assimilate glucose, acetic acid, butyric acid, and caproic acid as single carbon sources in synthetic medium with maximum PHAs production yields of 9–11%, on a cell dry weight basis. Single carbon sources were then replaced by a mixture of synthetic VFAs and by a VFAs-rich stream from the acidogenic fermentation of food waste. After 72 h of cultivation, the VFAs were almost fully consumed by the bacterium in both media and PHAs production yields of 9–10%, on cell dry weight basis, were obtained. The usage of VFAs mixture was found to be beneficial for the bacterial growth that tackled the inhibition of propionic acid, iso-butyric acid, and valeric acid when these volatile fatty acids were used as single carbon sources. The extracted PHAs were revealed to be polyhydroxybutyrate (PHB) by characterization methods of Fourier-transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). The obtained results proved the possibility of using VFAs from acidogenic fermentation of food waste as a cheap substrate to reduce the cost of PHAs production.
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| 17. |
- Wainaina, Steven, et al.
(author)
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Anaerobic digestion of food waste to volatile fatty acids and hydrogen at high organic loading rates in immersed membrane bioreactors
- 2020
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In: Renewable energy. - : Elsevier BV. - 0960-1481 .- 1879-0682.
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Journal article (peer-reviewed)abstract
- The organic loading rate (OLR) is an essential parameter that controls the anaerobic digestion process. This work investigated the performance of immersed membrane bioreactors operated at high OLRs of 4, 6, 8 and 10 g volatile solids (VS)/L/d regarding the fermentation behavior, product recovery and microbial dynamics during the acidogenic fermentation of food waste to volatile fatty acids (VFAs) and hydrogen. The highest yield of 0.52 g VFA/ gVSadded was attained at 6 g VS/L/d, while an optimal hydrogen yield of 14.7 NmL/ gVSadded was obtained at 8 g VS/L/d. The bacterial populations, analyzed using 16S rRNA gene amplicon sequencing, consisted mainly of Firmicutes and Actinobacteria at OLRs 4 and 8 g VS/L/d while Firmicutes, Actinobacteria and Proteobacteria phyla dominated at 6 and 10 g VS/L/d. Moreover, the presence of Clostridium and Lactobacillus genera correlated with the acetate, butyrate, caproate and lactate production.
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| 18. |
- Wainaina, Steven, et al.
(author)
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Automation and artificial intelligence in filamentous fungi-based bioprocesses: A review
- 2023
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In: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 369, s. 128421-128421
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Research review (peer-reviewed)abstract
- By utilizing their powerful metabolic versatility, filamentous fungi can be utilized in bioprocesses aimed at achieving circular economy. With the current digital transformation within the biomanufacturing sector, the interest of automating fungi-based systems has intensified. The purpose of this paper was therefore to review the potentials connected to the use of automation and artificial intelligence in fungi-based systems. Automation is characterized by the substitution of manual tasks with mechanized tools. Artificial intelligence is, on the other hand, a domain within computer science that aims at designing tools and machines with the capacity to execute functions that would usually require human aptitude. Process flexibility, enhanced data reliability and increased productivity are some of the benefits of integrating automation and artificial intelligence in fungi-based bio-processes. One of the existing gaps that requires further investigation is the use of such data-based technologies in the production of food from fungi.
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| 19. |
- Wainaina, Steven, et al.
(author)
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Biochemicals from food waste and recalcitrant biomass via syngas fermentation : A review
- 2017
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In: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976.
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Journal article (peer-reviewed)abstract
- An effective method for the production of value-added chemicals from food waste and lignocellulosic materials is a hybrid thermal-biological process, which involves gasification of the solid materials to syngas (primarily CO and H2) followed by fermentation. This paper reviews the recent advances in this process. The special focus is on the cultivation methods that involve the use of single strains, defined mixed cultures and undefined mixed cultures for production of carboxylic acids and higher alcohols. A rate limiting step in these processes is the low mass transfer between the gas and the liquid phases. Therefore, novel techniques that can enhance the gas-liquid mass transfer including membrane- and trickle-bed bioreactors were discussed. Such bioreactors have shown promising results in increasing the volumetric mass transfer coefficient (kLa). High gas pressure also influences the mass transfer in certain batch processes, although the presence of impurities in the gas would impede the process.[on SciFinder (R)]
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| 20. |
- Wainaina, Steven, et al.
(author)
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Bioengineering of anaerobic digestion for volatile fatty acids, hydrogen or methane production: A critical review
- 2019
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In: Bioengineered. - : Taylor & Francis Group. - 2165-5979 .- 2165-5987.
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Journal article (peer-reviewed)abstract
- Anaerobic digestion (AD) is a well-established technology used for producing biogas or biomethane alongside the slurry used as biofertilizer. However, using a variety of wastes and residuals as substrate and mixed cultures in the bioreactor makes AD as one of the most complicated biochemical processes employing hydrolytic, acidogenic, hydrogen-producing, acetate-forming bacteria as well as acetoclastic and hydrogenoclastic methanogens. Hydrogen and volatile fatty acids (VFAs) including acetic, propionic, isobutyric, butyric, isovaleric, valeric and caproic acid and other carboxylic acids such as succinic and lactic acids are formed as intermediate products. As these acids are important precursors for various industries as mixed or purified chemicals, the AD process can be bioengineered to produce VFAs alongside hydrogen and therefore biogas plants can become biorefineries. The current critical review paper provides the theory and means to produce and accumulate VFAs and hydrogen, inhibit their conversion to methane and to extract them as the final products. The effects of pretreatment, pH, temperature, hydraulic retention time (HRT), organic loading rate (OLR), chemical methane inhibitions, and heat shocking of the inoculum on VFAs accumulation, hydrogen production, VFAs composition, and the microbial community were discussed. Furthermore, this paper highlights the possible techniques for recovery of VFAs from the fermentation media in order to minimize product inhibition as well as to supply the carboxylates for downstream procedures.
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| 21. |
- Wainaina, Steven
(author)
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Developing a food waste-based volatile fatty acids platform using an immersed membrane bioreactor
- 2020
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Doctoral thesis (other academic/artistic)abstract
- Approximately 1.3 billion tons of food waste is produced globally every year. In principle, all the resources in the supply chain are lost (e.g. land, energy, and water) when the food is not consumed as intended. Anaerobic digestion is an established biological technology to treat food waste, and is mainly employed for recovery of energy in the form of biogas. Volatile fatty acids (VFAs) are formed as intermediate products of the anaerobic digestion process, and can be applied as precursors for various essential biomaterials. The manipulation of the anaerobic digestion process to synthesize these intermediates instead of biogas is considered to recover more value from food waste. However, some bottlenecks that prevent large-scale production and application of VFAs still exist. Among the key issues to be addressed are the difficulty in recovering the VFAs from the fermentation medium and the overall low product yields. The goals of the present thesis were: 1) to investigate methods to boost the production of VFAs from food waste; 2) to continuously recover VFAs from food waste fermentation medium; 3) to determine the changes in the microbial structure during high organic loading of food waste in membrane bioreactors; and 4) to study a novel approach for applying food waste-derived VFAs for cultivating edible filamentous fungi.For continuous product recovery at high yields, an immersed membrane bioreactor was constructed with robust cleaning capabilities to withstand the complex anaerobic digestion medium. The membrane bioreactor was first operated without pH control and a yield of 0.54 g VFA/g VSadded was achieved when an organic loading rate of 2 gVS/L/d was applied. Moreover, only a 16.4% reduction in the permeate flux during a 40-day operation period was recorded. In the second experimental work, the immersed membrane bioreactor system was subjected to high organic loading rates of 4, 6, 8, and 10 g VS/L/d as a tool of manipulating the anaerobic digestion process towards high VFAs and hydrogen production. The highest yield of VFAs was attained at 6 g VS/L/d (0.52 g VFA/gVSadded), while at 8 g VS/L/d, a maximal hydrogen yield of 14.7 NmL/gVSadded was obtained. An analysis of the microbial structure revealed that the presence of Clostridium resulted in high production of acetate, butyrate and caproate. On the other hand, the relative abundance of Lactobacillus was found to influence lactate biosynthesis.Cultivation of edible filamentous fungi presents a novel possibility for application of food waste-derived VFAs. Due to the growing demand of single-cell protein, one of the potential uses for the fungal biomass is the production of animal feed. In this thesis, an edible filamentous fungus, Rhizopus oligosporus was grown solely on the VFAs recovered from the membrane bioreactors. It was revealed that high concentrations could inhibit fungal growth; thus, the dilution of the VFAs solution used as substrate was necessary. Furthermore, when a fed-batch cultivation technique was applied, a four-fold improvement in the biomass production relative to standard batch cultivation was realized. A maximum biomass yield of 0.21 ± 0.01g dry biomass/ g VFAs COD eq. consumed, containing 39.28 ± 1.54% crude protein, was obtained. With further improvements in the VFAs uptake and the biomass yield, this novel concept could be a fundamental step in converting anaerobic digestion facilities into biorefineries.
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| 22. |
- Wainaina, Steven, et al.
(author)
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Food waste-derived volatile fatty acids platform using an immersed membrane bioreactor
- 2018
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In: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976.
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Journal article (peer-reviewed)abstract
- Volatile fatty acids (VFAs) are the key intermediates from anaerobic digestion (AD) process that can be a platform to synthesize products of higher value than biogas. However, some obstacles still exist that prevent large-scale production and application of VFAs, key among them being the difficulty in recovering the acids from the fermentation medium and low product yields. In this study, a novel anaerobic immersed membrane bioreactor (iMBR) with robust cleaning capabilities, which incorporated frequent backwashing to withstand the complex AD medium, was designed and applied for production and in situ recovery of VFAs. The iMBR was fed with food waste and operated without pH control, achieving a high yield of 0.54 g VFA/g VSadded. The continuous VFA recovery process was investigated for 40 days at OLRs of 2 gVS/L/d and 4 gVS/L/d without significant change in the permeate flux at a maximum suspended solids concentration of 31 g/L.
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| 23. |
- Wainaina, Steven, et al.
(author)
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Resource recovery and circular economy from organic solid waste using aerobic and anaerobic digestion technologies
- 2020
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In: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976.
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Journal article (peer-reviewed)abstract
- With the inevitable rise in human population, resource recovery from waste stream is becoming important for a sustainable economy, conservation of the ecosystem as well as for reducing the dependence on the finite natural resources. In this regard, a bio-based circular economy considers organic wastes and residues as potential resources that can be utilized to supply chemicals, nutrients, and fuels needed by mankind. This review explored the role of aerobic and anaerobic digestion technologies for the advancement of a bio-based circular society. The developed routes within the anaerobic digestion domain, such as the production of biogas and other high-value chemicals (volatile fatty acids) were discussed. The potential to recover important nutrients, such as nitrogen through composting, was also addressed. An emphasis was made on the innovative models for improved economics and process performance, which include co-digestion of various organic solid wastes, recovery of multiple bio-products, and integrated bioprocesses.
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| 24. |
- Wainaina, Steven, et al.
(author)
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Utilization of food waste-derived volatile fatty acids for production of edible Rhizopus oligosporus fungal biomass
- 2020
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In: Bioresource Technology. - : Elsevier BV. - 0960-8524 .- 1873-2976. ; 310
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Journal article (peer-reviewed)abstract
- Rhizopus oligosporus is an edible filamentous fungus that can contribute to meet the growing demand for single-cell protein. Volatile fatty acids (VFAs) are favorable potential substrates for producing R. oligosporus biomass due to their capacity to be synthesized from a wide range of low-value organic solid wastes via anaerobic digestion. The goal of this work was to cultivate R. oligosporus using food waste-derived VFAs as the sole carbon source. To maintain the requisite low substrate concentrations, the fed-batch cultivation technique was applied. This resulted in a four-fold improvement in biomass production relative to standard batch cultivation. Maximum biomass yield of 0.21 ± 0.01 g dry biomass/g VFAs COD eq. consumed, containing 39.28 ± 1.54% crude protein, was obtained. In the bubble-column bioreactors, the complete uptake of acetic acid was observed, while the consumptions of caproic and butyric acids reached up to 97.64% and 26.13%, respectively.
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| 25. |
- Yin, Dong-min, et al.
(author)
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The effect of mono- and multiple fermentation parameters on volatile fatty acids (VFAs) production from chicken manure via anaerobic digestion
- 2021
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In: Bioresource Technology. - : Elsevier. - 0960-8524 .- 1873-2976. ; 330
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Journal article (peer-reviewed)abstract
- Although the high nitrogen content of chicken manure (CM) poses major challenges for methane production through anaerobic digestion, on the bright side, it has a great potential for production of value-added intermediate products, such as volatile fatty acids (VFAs). However, in order to enhance VFAs yield, methane formation should be substantially suppressed. In the current research, individual and multiple effects of initial pH, heat-shock pretreatment, chemical methanogens inhibitor and the inoculum to substrate ratio (ISR) on optimization VFAs fermentation from CM were evaluated via batch assays. In this regard, the highest net VFAs yield, 0.53 g-VFA/g-VS, was achieved at conditions with heat-shocked inoculum and CM at ISR 1:6 and pH uncontrolled. Acetate dominated the VFAs mixture, accounting for up to 75% of total. Increased inoculum content enhanced the bioconversion efficiency to 78% at ISR 1:3. The study results suggest that alkalinity is a key promoter of VFAs production from CM.
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