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Bioconversion of gaseous effluents of oil-refinery by production of acids and alcohols from CO
Published in Samayita Chakraborty, Biovalorisation of liquid and gaseous effluents of oil refinery and petrochemical industry, 2021
After reaching a threshold concentration of 11.1 g/L ethanol, the cells started decaying with simultaneous reduction in the production of solvent-metabolites. The decay of the bacterial biomass may sometimes be attributed to the effect of solventogenic stress induced by the organic solvents produced (Alsaker et al., 2010). However, although a concentration of 11.1 g/L ethanol may exert some inhibition on gas fermenting clostridia, it has been shown that inhibition and eventually cell disruption can be limited at such modest ethanol concentrations (Fernández-Naveira et al., 2016b). Though the highest concentrations of butanol and hexanol, i.e., 1.18 g/L (41st day) and 1.46 g/L (42nd day), were achieved during the solventogenic stage, the concentrations of these alcohols dropped somewhat later for an unknown reason, which could have involved some butanol and hexanol degradation of, although this was not confirmed. Being more hydrophobic and hence more toxic to the bacterial cells, butanol and hexanol may perhaps also level off to a concentration that is nontoxic to the biomass (Willbanks et al., 2017). Microbial community analysis may give a better idea about the metabolism and operating strategies for optimum production of alcohols during CO fermentation.
Screening of symbiotic Streptomyces spp. and optimization of microalgal growth in a microalgae-actinomycetes co-culture system
Published in Preparative Biochemistry & Biotechnology, 2023
Chang Li, Ying Sun, Wenxiang Ping, Jingping Ge, Yimeng Lin
A suitable inoculation ratio can provide a good environment for the growth of microorganisms and the synthesis of target products in co-fermentation systems.[43] To investigate the effects of different inoculation ratios on the growth of Monoraphidium sp. HDMA-11, volume ratios of 5:1, 3:1, 1:1, 1:3, and 1:5 were used for microalgae–actinomycetes inoculation. Figure 4 shows the single-factor test results of the effects of different inoculation volume ratios on the growth of Monoraphidium sp. HDMA-11. Generally, the cell densities of the experimental groups were higher than those of the control group. Compared with other microalgae inoculation ratios, the two groups with the 1:3 (Figure 4D) and 1:5 (Figure 4E) inoculation volume ratios had fewer microalgae cells initially, with 4.80 × 106/mL and 2.80 × 106/mL, respectively. On the seventh day, the microalgae cell densities reached 8.40 × 107/mL and 9.70 × 107/mL, respectively, which were 1650.0 and 3364.3% higher than those on the first day. The experimental group with an inoculation ratio of 1:5 had a higher microalgae cell density increase than the other groups did. However, Monoraphidium sp. HDMA-11 treated with the 1:5 inoculation ratio had a lag period from day 0 to day 3 of culturing, and the microalgae cells grew rapidly from day 4 on. In contrast, Monoraphidium sp. HDMA-11 given the 1:3 treatment had a lag period from day 0 to day 2 in the co-culture system, with rapid growth on day 3. Considering the economic cost of culturing, early entry into the logarithmic phase can shorten the culture time and reduce the overall cost. Therefore, an inoculation ratio of 1:3 was selected as optimal for a co-culture system.
Saccharomyces cerevisiae and newly isolated Candida boidinii co-fermentation of industrial tea waste for improved bioethanol production
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2022
Ekin Demiray, Eda Açıkel, Sevgi Ertuğrul Karatay, Gönül Dönmez
To increase the bioethanol concentrations, co-fermentation strategy is an immature but promising method since it can increase ethanol yields and reduce overall process costs (Chen 2011). However, the lack of the bioethanol producer microorganisms which can produce cellulolytic enzymes or utilize both pentose and hexose sugars and high enzyme costs can be considered as limitations of the co-fermentation strategy.