Identification of Yeast and Mould Isolated from murcha in Nepal for Rice Wine Production

HIGHLIGHTS

• Two novel yeast strains were identified by sequencing for rice wine production.

• Rice wine (low alcohol by volume) was prepared from local raw materials of Nepal.

• Yeast and mould isolated from Parbat murcha showed potential fermentative characters.

Abstract

Rice wine is an alcoholic beverage made by simultaneous saccharification and fermentation by using mould and yeast, respectively. In Nepal, traditional starter culture locally known as murcha has been used for fermenting locally available raw materials such as millet, rice, wheat, etc. The quality of alcoholic beverages always varies due to the lack of process standardization in terms of culture and process. Here, isolation and screening of mould and yeast were done from the murcha collected from different districts of Nepal and used in the production of rice wine. The performance of mould was tested for saccharifying capacity and yeast for sugar, alcohol, pH tolerances and alcohol production. Most potent yeast isolates were identified by the molecular tool using 18s universal primer. Seven mould isolates from murcha were tested for saccharification by halo zone on starch media, microscopic observation, liquefication and dinitro salicylic acid test for identification of yeast and mould. All yeast isolates were also compared with commercial yeast (Saccharomyces bayanus SN9). Yeasts isolates from Parbat and Dolakha district murcha showed 99% identity with Saccharomyces boulardii and Saccharomyces cerevisiae respectively during basic local alignment search tool. Among eight isolates, murcha from Parbat sample showed better performance in terms of alcohol production. Yeast and mould from Parbat district were used for the fermentation of rice wine. During fermentation change in acidity, ˚Brix and pH respectively 1.0-2.6 g/L, 1-5 and 4.1-3.4. After pasteurized rice wine showed 5% abv, 1.5 g/L succinic acid, 0.27 g/L amino acid, 5.8 ˚Brix, 4.7 pH, 0.56 g/100 mL glucose with no detected methanol (g/100 L) while non pasteurized rice wine showed 5% abv, 1.3 g/L succinic acid, 0.34 g/L amino acid, 6 ˚Brix, 4.65 pH, 0.60 g/100 mL glucose with no detected methanol (g/100 L). Murcha sample collected from Parbat has highest potentail to produce sake campare to other sample collected from different district of Nepal.

Keywords:
Murcha; saccharification; fermentation; tolerance tests; rice wine