Isolation and characterization of halotolerant yeasts with alcohol fermentation ability

Lignocellulosic biomass is recognized as potentially sustainable source for the production of bioethanol, this innovative technology based on cellulosic biomass bioconversion to ethanol requires feedstock and microbial process. There are some agricultural processing residues, marine resources and saline crops with highly salt concentration, which are the potential as a feedstock if we want to use these kinds of material to produce cellulosic ethanol, we certainly need to find yeast strain which could tolerant high salt concentration.
168 yeast strains were isolated from three different kind of pickled liquid in Brassica juncea, sweet carambola, sour carambola, and respectively. 59 isolates were selected through progressive salt concentration assay and enzymatic screening of ethanol production assay. About 10 to 20 isolates randomly picked from each pickled liquids according to their analysis of 26S rDNA D1/D2 domain sequence by NCBI GenBank, these strains could belong to Candida, Pichia, Wickerhamomyces respectively.
Tiger 3, identity index was 99% with Pichia subpelliculosa, which shows the greatest ethanol production ability by HPLC. Also the physiological and biochemical characteristics of tiger 3 were measured. In the experiment of optimal alcohol fermentation conditions, the optimal temperature is 30℃, the optimal salt concentration is 7%. Under those conditions, the optimal fermentation pH value is 7, the ethanol production is 28.16 ± 0.76 g/L after 96 hours fermentation period.