Doskonalenie fermentacji etanolowej słomy rzepakowej

Przeprowadzono badania, których celem było określenie przydatności szczepu drożdży Pachysolen tannophilus KKP 546 do fermentacji hydrolizatów – pochodnych lignocelulozy ze słomy rzepakowej, poddanej łagodnej alkalicznej obróbce wstępnej. Proces fermentacji prowadzono w warunkach beztlenowych oraz tlenowych, stosując wytrząsanie z prędkością 120 obr.·min⁻¹ w celu zapewnienia równomiernego rozpuszczenie tlenu w podłożu. Efekty procesu fermentacji wyrażono ilością wytworzonego etanolu w medium poreakcyjnym. Po 96-godzinnej fermentacji brzeczek przygotowanych na bazie hydrolizatów słomy prowadzonych w warunkach tlenowych lub beztlenowych uzyskano średnio 1,54 oraz 1,64% v/v etanolu, przy sprawności całkowitej fermentacji na poziomie odpowiednio 56,44 i 60,23%.

Bioethanol has been recognized as a potential alternative to petroleum-derived transportation fuels. Cellulosic ethanol can be produced from almost any plant biomass, but favorable sources include wood chips, corn stover, rape and rice straw, grasses such as switchgrass and Miscanthus spp., garden clippings and food waste. Lignocellulose as a raw material is thus abundant, widely-distributed (often free) and readily replenished and sustainable because plants produce lignocellulose by first converting CO2 into sugars and then into polymers using the energy from sunlight. However, the production of ethanol from cellulose requires a greater amount of processing than first-generation biofuels fermented directly from starch and sugars. Specifically, the bottlenecks are the reduction of biomass to particles small enough to make enzymatic conversion efficient (i.e. comminution) followed by the conversion of lignocellulose into sugars ready for fermentation (i.e. saccharification). The yeasts traditionally used in fermentation processes are able to consume hexoses as substrate but not pentoses. Nevertheless, to obtain the fullest return from lignocellulose waste, within which there is a considerable hemicellulose fraction (18–34%) composed mainly of xylose, it is essential to resort to yeasts which also have the capacity to consume this pentose. To this end, Pachysolen tannophilus is capable of transforming d-xylose into useful bioproducts, such as ethanol and xylitol. The research was carried out with the aim of determining the utility of a strain of yeast P. tannophilus KKP 546 for fermentation of hydrolysates – derived from lignocellulose. The research material was rape straw after alkaline pretreatment. The hydrolysates of rape straw were fermented at 30°C, under anaerobic stationary conditions and aerobic conditions with shaking at 120 rpm for 96 h. The effects of the fermentation were expressed as the amount of ethanol produced in a fermentation medium. After a 96-hour fermentation of rape straw hydrolysates ethanol synthesis reached 1.54 and 1.64% v/v, with a total fermentation efficiency of 56.44 and 60.23%, for anaerobic and aerobic conditions respectively. The performance ability in ethanol production by P. tannophilus brings promising potential to ferment hydrolysate of lignocellulosic biomass. This study also provided information on rape straw utilization as an inexpensive potent substrate for the production of eco-friendly liquid fuel.