Evaluation of Thai agro-industrial wastes for bio-ethanol production by Zymomonas mobilis

Zymomonas mobilis is one of several microorganisms whose role in bio-ethanol production has been increasing in importance. Complex nutritional source for Z. mobilis could be substituted by many Thai agro-industrial wastes which are readily and inexpensively available. Their potentials as a yeast extract replacement were evaluated through the growth kinetics information. At equivalent level of total nitrogen (TN) (1.09 g TN l−1), ami-ami solution from glutamate-synthesizing process, autolysate of brewer's yeast and hydrolysate of fish soluble waste could support growth as effectively as 56, 61 and 96%, respectively, compared with the control. When utilizing these wastes, additional supplement of pantothenic acid (calcium salt) had no significant effect (P > 0.05) on growth improvement while urea (0.5 g l−1) supplied as ammonium sulfate replacement maintained satisfying growth of the organism and ethanol production. We observed that the fish soluble waste was the best applicable source of nutritional replacement for ethanol production since it could significantly promote both specific growth rate and ethanol productivity compared with the yeast extract.