Rice Straw from Saccharification to Ethanol Simultaneous Fermentation using Aspergillus neoellipticus and Saccharomyces cerevisiae

Abstract

One fungal isolate Am1 from compost identified as Aspergillus neoellipticus [GenBank accessed no. OM760561] was found to possess cellulytic activity of 5806 U (Fpase) when grown in submerged culture using treated rice straw (RS) as substrate. Under successive optimization steps including pH, nitrogen source type and C:N ratio, cellulytic activity increased by 1.4-fold recording 8237 U utilizing
yeast extract at pH 6 and C:N ratio of 1:0.9. Saccharification process using lyophilized raw cellulases produced by A. neoellipticus was optimized achieving saccharification efficiency of 89% at 50ºC and pH7. In a simultaneous saccharification fermentation process using 2L fermentor, optimized saccharification of RS was first held at an enzyme load of 25 U/ g RS after which Saccharomyces cerevisiae was used to ferment the resulting reducing sugar at a concentration of 10%. Optimized fermentation achieved fermentation efficiency of 99.2% at pH6 after 48 h, at a yield of 0.6g ethanol/g reducing sugar or 37.5 g ethanol/ 100 g RS.