| 1. |
- Aslanzadeh, S., et al.
(författare)
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A comparative study between single- and two-stage anaerobic digestion processes : Effects of organic loading rate and hydraulic retention time
- 2014
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Ingår i: International Biodeterioration & Biodegradation. - : Elsevier. - 0964-8305 .- 1879-0208. ; 95, s. 181-188
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Tidskriftsartikel (refereegranskat)abstract
- The effect of an organic loading rate (OLR) and a hydraulic retention time (HRT) was evaluated by comparing the single-stage and two-stage anaerobic digestion processes. Wastes from the food processing industry (FPW) and the organic fraction of the municipal solid waste (OFMSW) were used as substrates. The OLR was increased at each step from 2 gVS/l/d to 14 gVS/l/d, and the HRT was decreased from 10 days to 3 days. The highest theoretical methane yield achieved in the single-stage process was about 84% for the FPW during an OLR of 3 gVS/l/d at a HRT of 7 days and 67% for the OFMSW at an OLR of 2 gVS/l/d and a HRT of 10 days. The single-stage process could not handle a further increase in the OLR and a decrease in the HRT; thus, the process was stopped. A more stable operation was observed at higher OLRs and lower HRTs in the two-stage system. The OLR could be increased to 8 gVS/l/d for the FPW and to 12 gVS/l/d for the OFMSW, operating at a HRT of 3 days. The results show a conclusion of 26% and 65% less reactor volume for the two-stage process compared to the single-stage process for the FPW and the OFMSW, respectively.
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| 2. |
- Devanthi, P V P, et al.
(författare)
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Do Kombucha Symbiotic Cultures of Bacteria and Yeast Affect Bacterial Cellulose Yield in Molasses?
- 2021
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Ingår i: JOURNAL OF FUNGI. - : MDPI AG. - 2309-608X. ; 7:9
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Tidskriftsartikel (refereegranskat)abstract
- Bacterial cellulose (BC) is a valuable biopolymer typically observed in Kombucha with many potential food applications. Many studies highlight yeast's roles in providing reducing sugars, used by the bacteria to grow and produce BC. However, whether yeast could enhance the BC yields remains unclear. This study investigates the effect of yeast Dekkera bruxellensis on bacteria Komagataeibacter intermedius growth and BC production in molasses medium. The results showed that the co-culture stimulated K. intermedius by similar to 2 log CFU/mL, which could be attributed to enhanced reducing sugar utilization. However, BC yields decreased by similar to 24%, suggesting a negative impact of D. bruxellensis on BC production. In contrast to other studies, regardless of D. bruxellensis, K. intermedius increased the pH to similar to 9.0, favoring the BC production. Furthermore, pH increase was slower in co-culture as compared to single culture cultivation, which could be the reason for lower BC yields. This study indicates that co-culture could promote synergistic growth but results in the BC yield reduction. This knowledge can help design a more controlled fermentation process for optimum bacterial growth and, ultimately, BC production.
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| 3. |
- Jeihanipour, A, et al.
(författare)
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High-rate biogas production from waste textiles using a two-stage process
- 2013
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Ingår i: Renewable energy. - : Pergamon. - 0960-1481 .- 1879-0682. ; 52, s. 128-135
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Tidskriftsartikel (refereegranskat)abstract
- The efficacy of a two-stage Continuously Stirred Tank Reactor (CSTR), modified as Stirred Batch Reactor (SBR), and Upflow Anaerobic Sludge Blanket Bed (UASB) process in producing biogas from waste textiles was investigated under batch and semi-continuous conditions. Single-stage and two-stage digestions were compared in batch reactors, where 20 g/L cellulose loading, as either viscose/polyester or cotton/polyester textiles, was used. The results disclosed that the total gas production from viscose/polyester in a two-stage process was comparable to the production in a single-stage SBR, and in less than two weeks, more than 80% of the theoretical yield of methane was acquired. However, for cotton/polyester, the two-stage batch process was significantly superior to the single-stage; the maximum rate of methane production was increased to 80%, and the lag phase decreased from 15 days to 4 days. In the two-stage semi-continuous process, where the substrate consisted of jeans textiles, the effect of N-methylmorpholine-N-oxide (NMMO) pretreatment was studied. In this experiment, digestion of untreated and NMMO-treated jeans textiles resulted in 200 and 400 ml (respectively) methane/g volatile solids/day (ml/g VS/day), with an organic loading rate (OLR) of 2 g VS/L reactor volume/day (g VS/L/day); under these conditions, the NMMO pretreatment doubled the biogas yield, a significant improvement. The OLR could successfully be increased to 2.7 g VS/L/day, but at a loading rate of 4 g VS/L/day, the rate of methane production declined. By arranging a serial interconnection of the two reactors and their liquids in the two-stage process, a closed system was obtained that converted waste textiles into biogas.
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