Process Optimization of Bioethanol Production by Stress Tolerant Yeasts Isolated From Agro-Industrial Waste

Abstract

The need of Bioethanol or biofuel is increasing worldwide day by day due to renewable resources and ease of production form cheap raw materials. There are several factors that affect on bioethanol production by using yeast. The main objective of this research work was to isolate stress tolerant yeast from agro industry and optimize a process for ethanol production by considering all the factors. Several fermentation batches were carried out by 3 stress tolerant strains varying temperature, pH, sugar concentration, aeration, immobilization and metal ions. From different experiments it was found that temperature 30°C, reducing sugar concentration ranged between 5-6%, pH between 5.0 - 6.0 and shaking condition were optimum for maximum yield of ethanol by strains Saccharomyces unisporous (P), Saccharomyces cerevisiae (C) and (T).The Bioethanol production capacity of yeasts were found P -15.00%, C -12.50% and T – 10.15%at pH 6.0, 30oC temperature in media with 5.5% initial reducing sugar concentration in shaking condition (115 rpm).Pilot scale ethanol production by P strain was 13.10%, C strain 11.15% andT strain 9.80% at 60 hours. Immobilized cells were produced more ethanol than free cells with same culture conditions. Effect of potassium, magnesium, chromium and boron was investigated on ethanol production. Potassium, Magnesium was shown stimulatory effect on ethanol production.