| 1. |
- Marhendraswari, M. B.D., et al.
(författare)
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Production of edible fungal (Rhizopus delemar CBS 145940) biomass from organosolv-pretreated oil palm empty fruit bunch (OPEFB) in submerged fermentation
- 2020
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Ingår i: IOP Conference Series: Materials Science and Engineering. - : Institute of Physics (IOP). - 1757-8981 .- 1757-899X. ; 991:1
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Konferensbidrag (refereegranskat)abstract
- Accumulation of oil palm empty fruit bunches (OPEFB) from palm oil industry poses challenges for the disposal process, which leads to environmental damage. For this reason, valorization of OPEFB fractions to produce edible fungal biomass was carried out in this research. The fungus was Rhizopus delemar CBS 145940, which is an edible fungus, Indonesian indigenous, and is favorable for the production of several end products. Organosolv pretreatment was first conducted on OPEFB using ethanol (50%) as the solvent. Enzymatic hydrolysis was then performed using Cellic® Ctec3 on the pretreated-OPEFB fractions. Hydrolyzates from cellulose-rich fraction, slurry (a mixture of cellulose-rich fraction and hemicellulose-rich fraction), and hemicellulose-rich fraction were used as the cultivation media for fungal growth. The corresponding yield of fungal biomass from each medium was 0.62 ± 0.07 g/g glucose; 0.41 ± 0.02; and 0.61 ± 0.13 g/g fermentable sugars, respectively. These results showed that Rhizopus delemar CBS 145940 could be grown in all the hydrolyzates from the OPEFB fractions. Nevertheless, in order to obtain higher fungal biomass, supplementation of nutrition was needed.
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| 2. |
- Millati, Ria, 1972, et al.
(författare)
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Anaerobic digestion of citrus waste using two-stage membrane bioreactor
- 2018
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Ingår i: IOP Conference Series: Materials Science and Engineering. - 1757-8981 .- 1757-899X. ; 316:1
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Konferensbidrag (refereegranskat)abstract
- Anaerobic digestion is a promising method to treat citrus waste. However, the presence of limonene in citrus waste inhibits anaerobic digestion process. Limonene is an antimicrobial compound and could inhibit methane forming bacteria that takes a longer time to recover than the injured acid forming bacteria. Hence, volatile fatty acids will be accumulated and methane production will be decreased. One way to solve this problem is by conducting anaerobic digestion process into two stages. The first step is aimed for hydrolysis, acidogenesis, and acetogenesis reactions and the second stage is aimed for methanogenesis reaction. The separation of the system would further allow each stage in their optimum conditions making the process more stable. In this research, anaerobic digestion was carried out in batch operations using 120 ml-glass bottle bioreactors in 2 stages. The first stage was performed in free-cells bioreactor, whereas the second stage was performed in both bioreactor of free cells and membrane bioreactor. In the first stage, the reactor was set into 'anaerobic' and 'semi-aerobic' conditions to examine the effect of oxygen on facultative anaerobic bacteria in acid production. In the second stage, the protection of membrane towards the cells against limonene was tested. For the first stage, the basal medium was prepared with 1.5 g VS of inoculum and 4.5 g VS of citrus waste. The digestion process was carried out at 55°C for four days. For the second stage, the membrane bioreactor was prepared with 3 g of cells that were encased and sealed in a 3×6 cm 2 polyvinylidene fluoride membrane. The medium contained 40 ml basal medium and 10 ml liquid from the first stage. The bioreactors were incubated at 55°C for 2 days under anaerobic condition. The results from the first stage showed that the maximum total sugar under 'anaerobic' and 'semi-aerobic' conditions was 294.3 g/l and 244.7 g/l, respectively. The corresponding values for total volatile fatty acids were 3.8 g/l and 2.9 g/l, respectively. Methane production of citrus waste taken from the first stage under 'anaerobic' condition in membrane and free-cells bioreactors was 11.2 Nml and 7.2 Nml, respectively. Whereas, methane production of citrus waste taken from the first stage under 'semi-aerobic' condition in membrane and free-cells bioreactors was 8.8 Nml and 5.7 Nml, respectively. It can be seen from the results of the first stage that volatile fatty acids from 'anaerobic' condition was higher than that of 'semi-aerobic' condition. The absence of oxygen provides the optimal condition for growth and metabolism of facultative and obligatorily anaerobic bacteria in the first stage. Furthermore, polyvinylidene fluoride membrane was able to protect the cells from antimicrobial compounds.
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| 3. |
- Westman, Johan O., et al.
(författare)
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Encapsulated vs. free yeast : A comparative proteomic study
- 2011
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Ingår i: International PhD course in Industrial Biotechnology for lignocellulose based processes, October 16-21, Göteborg, Sweden.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In the search for a replacement for fossil fuels, due to their depletion as well as an increased concern about our environment, 2nd generation bioethanol comes out as one of the most promising alternatives. There are challenges in several steps of lignocellulose processing – especially due to the formation of for yeast inhibitory compounds during pretreatment and hydrolysis. It has previously been shown that encapsulation of the yeast in membranes made of an alginate gel enables the yeast to survive otherwise toxic hydrolysates. The physiological changes arising from encapsulation are however largely unknown, although it has been shown that the macromolecular composition of the yeast changes during prolonged cultivation. In this study we have therefore performed a comparative proteomic study of yeast grown in capsules and in suspension in anaerobic batch cultivations.
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| 4. |
- Westman, Johan O., et al.
(författare)
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Inhibitor tolerance and flocculation : Characterization of a yeast strain suitable for 2nd generation bioethanol production
- 2011
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Ingår i: Abstract book, Joint poster exhibition at the Dept Chemical and Biological Engineering, Chalmers University of Technology, and Dept Chemistry, University of Gothenburg. April 12, Göteborg, Sweden.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Robust second generation bioethanol processes require microorganisms able to obtain high yields and production rates while fermenting inhibiting hydrolysates. However, tolerance towards inhibitors like, carboxylic acids, furan aldehydes and phenolic compounds, is still an issue and the factors contributing to improved tolerance are not well known. In this study, the constitutively flocculating Saccharomyces cerevisiae strain CCUG 53310, with good ability to ferment toxic hydrolysates, was compared with S. cerevisiae CBS 8066 in order to characterize the mechanisms of flocculation and the fermentative performance in different inhibitory media. The flocculation of CCUG 53310 depended on cell wall proteins and was partly inhibited by mannose. The flocculating cells also exhibited a significantly higher hydrophobicity than the cells of the non-flocculating strain CBS 8066, which might contribute to the flocculation. The flocculating strain was more tolerant to carboxylic acids and furan aldehydes, but more sensitive to phenolic compounds. Surprisingly, the expression increase of YAP1, ATR1 and FLR1, known to confer resistance against lignocellulose-derived inhibitors, upon addition of various inhibitors to the fermentation medium, was less in CCUG 53310 than in CBS 8066 in most cases. This indicates that the flocculating strain experienced the cultivation conditions as less stressful. The flocculation in itself is a likely cause of this by creating subinhibitory local levels of inhibitors for most cells, allowing the cells in flocs to experience a lower collective stress level.
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