Selection and Characterization of Endomycopsis fibuligera Strains for One‐step Fermentation of Starch to Ethanol

Abstract

AbstractIn a step‐wise systematic selection, a strain of Endomycopsis fibuligera NRRL 76 was found to be better than the other strains tested in the production of α‐amylase and glucoamylase as well as ethanol directly from sugary and starchy substrates. Comparatively, the strain tolerated more ethanol. converted more starch to ethanol, produced less biomass and did not assimilate ethanol. There was an interrelationship between qualitative and quantitative production of amylases and ethanol production in batch fermentation with various strains. The constitutive nature of glucoamylase produced. Us lack of catabo‐lite repression and resistance to ethanol inhibition as well as the nature of starch hydrolytic products obtained, appeared to be important characteristic features in the strain for efficient conversion of starch directly to ethanol.Among a wide range of starchy substrates used in ethanol production by the yeast strains, cassava starch and waxy rice were found to be more suitable.When the strain NRRL 76 was grown optimally at pH 6.0 and 30C for 1 d under aeration followed by 3d without aeration, the maximum ethanol concentration was 92.0g/L and 73.5 g/L in media containing 300g/L and 200g/L of cassava starch respectively as compared to 73.5g/L and 77.3g/L of ethanol by another promising strain of Schwanniomyces castellii ATCC 26077, under similar set of conditions. This process of NRRL 76 was compared with other one step processes reported in literature and found to be better than the others. The strain also converted high concentrations of cassava starch (up to 400g/L) and also waxy rice (250g/L) to ethanol satisfactorily.