Evaluation of ethanol fermentation efficiency of sweet sorghum syrups produced by integrated dual-membrane system

1G ethanol from sweet sorghum can be a better alternative to various other sources used for its production. The commercial feasibility is dictated by the high sugar containing varieties, their transport to ethanol plants, storage and availability of robust yeast strains for the fermentation. Eight sweet sorghum cultivars namely CSV19SS, CSV24SS, CSV27, CSV32F, PV, SSV84, RVICSH, SPV1871, SSV74 were tested for their sugar content and varieties-SSV84 and CSV24SS were containing sugar content of 170-190 g/L. Specifically designed polyethersulfone-based ultrafiltration (UF) membrane and hydrophilised polyamide (HPA-150) also termed as nanofiltration (NF) membrane were synthesized by interfacial polymerization technique and were used for the concentration of sweet sorghum juice. The syrup retained on an average 90% sugars at 4 degrees C, 100% at - 20 degrees C for 6 months and 10% at room temperature for 36 h. The overall product yield of ethanol ranged between 0.48 and 0.49 g/g in batch fermentation in a 14 L reactor.