| 1. |
- Millati, R., et al.
(author)
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Pretreatment technologies for anaerobic digestion of lignocelluloses and toxic feedstocks
- 2020
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In: Bioresource Technology. - : Elsevier Ltd. - 0960-8524 .- 1873-2976. ; 304
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Journal article (peer-reviewed)abstract
- Several feedstocks for anaerobic digestion (AD) have challenges that hamper the success of AD with their low accessible surface area, biomass recalcitrance, and the presence of natural inhibitors. This paper presents different types of pretreatment to address those individual challenges and how they contribute to facilitate AD. Organosolv and ionic liquid pretreatments are effective to remove lignin without a significant defect on lignin structures. To deal with accessible surface area and crystallinity, comminution, steam explosion, pretreatment using N-methyl-morpholine-N-oxide methods are suggested. Moreover, solid extraction, simple aeration, and biological treatments are capable in removing natural inhibitors. Up to date, methods like comminution, thermal process, and grinding are more preferable to be scaled-up. © 2020 Elsevier Ltd
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| 2. |
- Millati, R., et al.
(author)
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Anaerobic digestion biorefinery for circular bioeconomy development
- 2023
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In: Bioresource Technology Reports. - : Elsevier. - 2589-014X. ; 21
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Journal article (peer-reviewed)abstract
- This paper presents an overview of the concept of biorefinery based on anaerobic digestion (AD) process that converts various wastes from easily degradable to challenging materials as well as carbon dioxide into many valuable products. Anaerobic digestion produces volatile fatty acids, biohydrogen, biogas, and biosludge. Factors that affect the production process, the reactor system, and the downstream process to obtain the desired product are discussed. Future applications of the AD products and their derivatives as biofuels, biochemicals, biomaterials, and biofertilizer as well as the market size are presented. Implementation of AD biorefinery is potentially accelerate the achievement of sustainable development goals, especially in the areas of clean water and sanitation, affordable and clean energy, and climate change.
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| 3. |
- Wikandari, R., et al.
(author)
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Biogas production from citrus waste by membrane bioreacto
- 2014
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In: Membranes. - : MDPIAG. - 2077-0375. ; 4:3, s. 596-607
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Journal article (peer-reviewed)abstract
- Rapid acidification and inhibition by d-limonene are major challenges of biogas production from citrus waste. As limonene is a hydrophobic chemical, this challenge was encountered using hydrophilic polyvinylidine difluoride (PVDF) membranes in a biogas reactor. The more sensitive methane-producing archaea were encapsulated in the membranes, while freely suspended digesting bacteria were present in the culture as well. In this membrane bioreactor (MBR), the free digesting bacteria digested the citrus wastes and produced soluble compounds, which could pass through the membrane and converted to biogas by the encapsulated cell. As a control experiment, similar digestions were carried out in bioreactors containing the identical amount of just free cells. The experiments were carried out in thermophilic conditions at 55 °C, and hydraulic retention time of 30 days. The organic loading rate (OLR) was started with 0.3 kg VS/m3/day and gradually increased to 3 kg VS/m3/day. The results show that at the highest OLR, MBR was successful to produce methane at 0.33 Nm3/kg VS, while the traditional free cell reactor reduced its methane production to 0.05 Nm3/kg VS. Approximately 73% of the theoretical methane yield was achieved using the membrane bioreactor.
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| 4. |
- Wikandari, R., et al.
(author)
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Pretreatment of Lignocelluloses With Solvent N-Methylmorpholine N-oxide
- 2016
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In: Biomass Fractionation Technologies for a Lignocellulosic Feedstock Based Biorefinery. - : Elsevier Inc.. - 9780128025611 - 9780128023235
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Book chapter (peer-reviewed)abstract
- Three decades after N-methylmorpholine N-oxide (NMMO) was first introduced as a solvent for direct cellulose dissolution, the usage of NMMO in the fiber-making industry has flourished throughout the world. This success attracts the attention of researchers working in lignocellulosic biomass fractionation to use NMMO as an agent for lignocellulosic pretreatment in biofuel production. The present chapter presents the current status of NMMO for the pretreatment of lignocellulosic biomass for further fermentation to biofuels.
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| 5. |
- Hellwig, Coralie, et al.
(author)
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Household fermentation of leftover bread to nutritious food
- 2022
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In: Waste Management. - : Elsevier BV. - 0956-053X .- 1879-2456. ; 150, s. 39-47
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Journal article (peer-reviewed)abstract
- Resource dependency of food production is aggravated when food is wasted. In Sweden, it is estimated that 37% of the total bread waste is generated at the household level. This work aimed to assess whether fermentation using edible filamentous fungi at households can provide a solution to valorize leftover bread in the production of fungi-based food for consumption. Bread was fermented in household and laboratory conditions with Neurospora intermedia and Rhizopus oligosporus. The results show that bread can be successfully and easily fermented at households, without signs of microbial contamination even though the conditions were not sterile. Fermentation at the household resulted in higher protein, fat and fiber content as well as greater starch reduction compared to the samples fermented under laboratory conditions. Household engagement in bread fermentation will likely depend on values that motivate reusing leftover bread. Perceived values that are expected to motivate engagement vary across individuals, but may include improved nutritional benefits, food waste prevention, convenience, responsibilities, and being part of sustainable societies and actions. © 2022 The Author(s)
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| 6. |
- 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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| 7. |
- Wikandari, R., et al.
(author)
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Assessment of microbiological quality and mycotoxin in dried chili by morphological identification, molecular detection, and chromatography analysis
- 2020
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In: International Journal of Environmental Research and Public Health. - : MDPI AG. - 1661-7827 .- 1660-4601. ; 17:6
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Journal article (peer-reviewed)abstract
- The growing interest in spicy foods leads to the global demand for spices, particularly dried chili. This study aimed to assay both aflatoxin (AFs) and ochratoxin A (OTA) contamination using an integrative method of morphological identification, molecular detection, and chromatography analysis on dried chili provided from traditional and modern markets in Indonesia. The results showed that total fungal infection ranged from 1-408 × 103 CFU/g. Eighty percent of the chili obtained from both the traditional and the modern markets were infected by Aspergillus spp., in which 50% of the infections were identified as A. parasiticus and A. flavus. A complete set of targeted genes involved in AF production and OTA were detected in two isolates of A. flavus and one isolate of A. carbonarius, respectively. The levels of AFs B1, B2, and OTA in the contaminated dried chilies were in the range of 39.3–139.5 µg/kg, 2.6–33.3 µg/kg, and 23.7–84.6 µg/kg, respectively. In contrast, no AFs G1 and G2 were detected. This study showed that the fungal infection of Indonesian dried chili occurs both in the field and during storage; thus, it is suggested to implement good agricultural and handling processes. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.
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| 8. |
- Wikandari, Rachma, et al.
(author)
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Biogas production from fruit wastes : fruit flavors as booster or inhibitors?
- 2012
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Conference paper (peer-reviewed)abstract
- In order to improve biogas production from fruit waste, investigation of effect of fruit flavors on biogas production was carried out. The work was performed in batch anaerobic digestion using synthetic medium and thermophilic bacteria for 30 days. Twelve different flavors belonging to aldehydes (hexanal, nonanal, and E-2- hexenal), terpenes (carene, α-pinene, and myrcene), alcohol (octanol), lactone (furanone), and esters (methyl butyrate, ethyl butyrate, ethyl hexanoate, and hexyl acetate) were tested. Anaerobic digestion without addition of flavors was used as reference. For aldehyde groups, hexanal and nonanal showed inhibition effect at concentration of 0.005% whereas E-2-hexenal required higher concentration i.e. 0.05% to show its effect. Addition of 0.5% of hexanal, nonanal, and E-2-hexenal resulted in lower biogas production than that of the corresponding reference by factor of 276, 317 and 434%, respectively. Similar to aldehydes, all terpenes group showed inhibition at concentration of 0.005%. Addition of 0.5% of carene, α-pinene, and myrcene decreased biogas production by factor of 300, 255, and 330%, respectively compared to the reference. Moreover, in the presence of 0.5% of octanol and furanone reduced biogas production by factor of 433 and 183%, respectively compared to the reference. On the contrary, higher biogas production was obtained by addition of all esters tested. Methyl butyrate, ethyl butyrate, ethyl hexanoate, and hexyl acetate at concentration of 0.5% increased biogas production by factor of 291, 717, 542, and 640%, respectively compared to the reference. In conclusion, most of flavor compounds are inhibitor for biogas production for the exception of ester groups.
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| 9. |
- Wikandari, Rachma, et al.
(author)
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Fermentation inhibitors in ethanol and biogas processes and strategies to counteract their effects
- 2019
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Book (other academic/artistic)abstract
- Bioethanol and biogas production are the most common fermentation process to convert organic waste into energy. The presence of inhibitory compounds affects the performance of fermentation, leading to lower product yield. The inhibitory compounds for bioethanol and biogas might be different due to the different types of microorganism used for the process, in which bioethanol process uses a single culture, while biogas process uses a mix culture of microorganisms. However, in general, the inhibitors can be classified into three groups. The first group is natural inhibitor exist in the raw material such as flavor compounds or chemical compounds that contaminates available in the waste stream such as heavy metals, light metals, antibiotics, and pesticides. The second group is inhibitor that forms during the fermentation process such as ammonia, sulfide, and ethanol. The third group is inhibitor which is formed during the pretreatment of lignocellulose such as furfural, hydroxymethylfurfural, phenolic compounds, and humic acid. The minimum inhibitory concentration and inhibition mechanism will be discussed in this chapter. The inhibition effects can be reduced or removed by choosing a suitable concentration of the substrates and choosing a proper method for the pretreatment and/or hydrolysis steps. When the toxic compounds are available in the substrate, detoxification could be an option, although it has some expenses and might lead to partial loss of sugars. However, choosing a right strategy for the fermentation by selecting a suitable process, for example, fed-batch or continuous mode with high cell density or encapsulated cells, using a tolerant organism or an organism that can convert the inhibitors, might avoid the necessity of detoxification.
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| 10. |
- Wikandari, Rachma, et al.
(author)
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Inhibitory Effect of Fruit Flavors on Methane Production During Anaerobic Digestion
- 2013
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In: Bioresource Technology. - : Elsevier. - 0960-8524 .- 1873-2976. ; 145:IFIBiop, s. 188-192
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Journal article (peer-reviewed)abstract
- In order to improve biogas production from fruit wastes, the inhibitory effects of fruit flavors on anaerobic digestion were investigated. Batch anaerobic digestion was performed for 30 days using synthetic medium and thermophilic sludge. Three groups of flavor compounds i.e. aldehydes (hexanal, nonanal, and E-2-hexenal), terpenes (car-3-ene, α-pinene, and myrcene), and alcohol (octanol) at concentration of 0.005%, 0.05%, and 0.5% were examined. All the flavor compounds showed inhibitory effect on methane production. The highest methane reduction was obtained at addition of 0.5% of flavor compounds. For terpenoids, the presence of 0.5% of car-3-ene, myrcene, and α-pinene reduced 95%, 75%, and 77% of methane production, respectively. For aldehydes, addition of 0.5% concentration resulted in more than 99% methane reduction for hexanal and E-2-hexenal, and 84% methane reduction for nonanal. For alcohol, the presence of 0.5% octanol decreased 99% methane production.
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