Optimized fermentation strategies for efficient bioethanol production

Document Type : Original Article

Authors

1 Hospira Healthcare Pvt. Ltd, Chennai, Tamil Nadu 600017, India.

2 Badrinarayan Barwale Mahavidhyalaya, Jalna 431213, Maharashtra, India

Abstract

Energy is essential for economic growth and sustainable development. The conventional finite exhaustible resources such as petroleum, natural gas, and coal dominate the global energy supply but are limited and geographically dispersed. India has turned to sustainable alternatives like ethanol blending to reduce dependency on imported oil. Bioethanol production leverages lignocellulosic biomass through enzymatic saccharification, fermentation, and pre-treatment processes. This study investigates bioethanol production using a wild Escherichia coli strain isolated from the Cooum River, employing a fed-batch fermentation method to optimize yield and efficiency. Samples of cellulose-rich compost and Cooum River water were collected to isolate microbial strains for fermentation trials. E. coli isolates were purified using nutrient agar and characterized microscopically and biochemically. Fermentation was carried out in controlled batches and continuous reactors, using various nutrient combinations. Key process parameters like pH, temperature, and RPM were optimized using Response Surface Methodology (RSM) to maximize ethanol yield. The study extensively analyzed ethanol production using various microbial strains and fermentation conditions. Batch operation with E. coli FBWHR and sugar maple hydrolysate revealed optimal ethanol production (20.38 g/L) at 50% sugar concentration, with sequential sugar utilization. Levoglucosan fermentation by E. coli KO11 achieved a 40% theoretical yield, prompting comparative studies with Zymomonas mobilis. Continuous operation with E. coli FBR5 using wheat straw hydrolysate (WSH) produced stable ethanol yields (~19.2 g/L), improved by desalting. Salt tolerance (up to 40 g/L NaCl) and xylose tolerance (250 g/L) were noted. Regression analysis highlighted key factors like sugar utilization, ethanol yield, and cell mass influencing productivity. This study highlights the critical role of substrate optimization, inhibitor removal, and strain engineering in enhancing ethanol productivity under varying fermentation conditions, aligning with prior findings on microbial robustness and process efficiency.

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