Optimization of fermentation parameters for bioethanol production from waste glycerol by microwave induced mutant Escherichia coli

Abstract

Biodiesel being one of the most promising alternative and renewable biofuels has lately seen rapid increase in its production capacity. Along with that there has also been a great increase in production of the co-product, crude glycerol. More attention is being paid to the utilization of crude glycerol from biodiesel production in order to defray the production cost of biodiesel and to promote biodiesel industrialization on a large scale. Bioconversion of crude glycerol to bioethanol through microbial fermentation is a very promising application of glycerol. The yield of bioethanol from fermentation of glycerol is greatly influenced by various parameters such as temperature, pH, glycerol concentration, organic nutrient concentration, and agitation speed and the bacterial species. The present study was undertaken to investigate optimum parameters for bioethanol production from raw glycerol (biodiesel by-product) by mutant Escherichia coli (E.coli) (ATCC11505) strain immobilized on chitosan optimized by Taguchi statistical method. The initial parameters were set each at four levels and the orthogonal array layout of L16 (45) was conducted. The result indicated that the significant controlling parameters for optimizing the operational fermentation were temperature 36°C, medium pH 7.0, initial glycerol concentration (250 g/l), and organic source concentration (5 g/l). The predicted value of bioethanol production under optimized conditions was (117.6 g/l). Immobilized cells are mainly used for economic benefits of continuous production or repeated use in continuous as well as in batch mode.