Бурение грунтовых зондов, установка энергетических колодцев

Selected examples of continuous fermentation in cellulosic ethanol production are shown in Table 9.3.

9.2.2 Continuous Fermentation Using Immobilized Microorganisms

Continuous fermentation using immobilized microorganisms is an interesting development in fermenter configuration and design research as this can dramatically reduce the ethanol production costs. There are some recent examples in the use of plug flow reac­tors with immobilized bacteria or yeast to produce ethanol via SHF and SSF paths [25,21,26-28]. In a recent illustration of using immo­bilized microorganisms, Crespo and coworkers used an anaerobic bacterium Caloramator boliviensis for fermentation of pure sugars and a pentose-rich sugarcane bagasse hydrolyzate [21]. In this experiment fermentations were carried out in a packed bed reactor with immobilized cells of C. boliviensis. They reported that more than 98% of substrates were converted and ethanol yields of 0.40­

0. 46 g/g of sugar were obtained when sugarcane bagasse hydroly­zate was fermented [21].

There are a number of interesting examples of using immobilized yeast in continuous fermentation reactors. In an experiment involv­ing calcium alginate immobilized yeast strain S. cerevisiae CBS 8066, Taherzadeh et al. reported the fermentation of a dilute acid hydroly — zate in a CSTR at dilution rates of 0.3, 0.5, and 0.6 h-1; these dilution rates resulted in 86, 83, and 79% sugar consumptions, respectively. The ethanol yield was between 0.45 and 0.48 g/g. Furthermore, hydrolyzate was fermentable at a dilution rate of 0.1 h-1 in a free-cell system but washed out at a dilution rate of 0.2 h-1 [29]. In another example, Talebnia and Taherzadeh used calcium alginate encap­sulated S. cerevisiae CBS 8066 cells in continuous hydrolyzate fer­mentation at dilution rates of 0.1, 0.2, 0.3, 0.4, and 0.5 h-1; glucose conversion dropped from 95% to 71% and mannose conversion from 98% to 79% over this range. Additionally, they reported an

increase in ethanol productivity from 1.1 to 4.2 g L-1 h-1 with the ris­ing dilution rate [30].

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