Simultaneous utilization of galactose and glucose bySaccharomyces spp

Ethanol production from banana peels using statistically optimized simultaneous saccharification and fermentation process

Dried and ground banana peel biomass (BP) after hydrothermal sterilization pretreatment was used for ethanol production using simultaneous saccharification and fermentation (SSF). Central composite design (CCD) was used to optimize concentrations of cellulase and pectinase, temperature and time for ethanol production from BP using SSF. Analysis of variance showed a high coefficient of determination (R(2)) value of 0.92 for ethanol production. On the basis of model graphs and numerical optimization, the validation was done in a laboratory batch fermenter with cellulase, pectinase, temperature and time of nine cellulase filter paper unit/gram cellulose (FPU/g-cellulose), 72 international units/gram pectin (IU/g-pectin), 37 °C and 15 h, respectively. The experiment using optimized parameters in batch fermenter not only resulted in higher ethanol concentration than the one predicted by the model equation, but also saved fermentation time. This study demonstrated that both hydrothermal pretreatment and SSF could be successfully carried out in a single vessel, and use of optimized process parameters helped achieve significant ethanol productivity, indicating commercial potential for the process. To the best of our knowledge, ethanol concentration and ethanol productivity of 28.2 g/l and 2.3 g/l/h, respectively from banana peels have not been reported to date.

Enhanced ethanol production from sugarcane juice by galactose adaptation of a newly isolated thermotolerant strain of Pichia kudriavzevii

The thermotolerant yeast strain isolated from sugarcane juice through enrichment technique was identified as a strain of Pichiakudriavzevii (Issatchenkiaorientalis) through molecular characterization. The P. kudriavzevii cells adapted to galactose medium produced about 30% more ethanol from sugarcane juice than the non-adapted cells. The recycled cells could be used for four successive cycles without a significant drop in ethanol production. Fermentation in a laboratory fermenter with galactose adapted P. kudriavzevii cells at 40°C resulted in an ethanol concentration and productivity of 71.9 g L(-1) and 4.0 g L(-1)h(-1), respectively from sugarcane juice composed of about 14% (w/v) sucrose, 2% (w/v) glucose and 1% (w/v) fructose. In addition to ethanol, 3.30 g L(-1) arabitol and 4.19 g L(-1) glycerol were also produced, whereas sorbitol and xylitol were not formed during fermentation. Use of galactose adapted P. kudriavzevii cells for ethanol production from sugarcane juice holds potential for scale-up studies.

Enhanced ethanol production from Kinnow mandarin (Citrus reticulata) waste via a statistically optimized simultaneous saccharification and fermentation process

Dried, ground, and hydrothermally pretreated Kinnow mandarin (Citrus reticulata) waste was used to produce ethanol via simultaneous saccharification and fermentation (SSF). Central composite design was used to optimize cellulase and pectinase concentrations, temperature, and time for SSF. The D-limonene concentration determined with high-performance liquid chromatography (HPLC) for fresh, dried, and pretreated biomass was 0.76%, 0.32%, and 0.09% (v/w), respectively. Design Expert software suggested that the first-order effect of all four factors and the second-order effect of cellulase and pectinase concentrations were significant for ethanol production. The validation experiment using 6 FPU gds(-1) cellulase and 60 IU gds(-1) pectinase at 37 °C for 12 h in a laboratory batch fermenter resulted in ethanol concentration and productivity of 42 g L(-1) and 3.50 g L(-1) h(-1), respectively. Experiments using optimized parameters resulted in an ethanol concentration similar to that predicted by the model equation and also helped reduce fermentation time.