Analysis of Arhar Stem (Cajanus cajan) for Bio-Ethanol Production Using Fermentation Process

Aim/Background: The rising cost of crude oil and increasing energy demand are driving interest in alternative bioenergy sources. Agriculture forms the backbone of India’s economy, and the country is the largest producer and consumer of pigeon peas (Cajanus cajan), accounting for over 70% of global production. Agricultural residues, particularly Cajanus cajan stalks, which constitute a significant portion of biomass, present a promising feedstock for bioenergy. Utilizing such residues for biofuel production could reduce India’s dependency on fossil fuel imports and support sustainable energy goals. This research explores the viability of fermenting agricultural residues like Arhar stem (Cajanus cajan) to produce bioethanol. Methods: The process involves the pretreatment of Arhar stem (Cajanus cajan) to split its complex cellulose and hemicellulose structures into fermentable sugars. Enzymatic hydrolysis was performed, followed by fermentation using Saccharomyces cerevisiae. For yeast cultivation and screening, Baker's yeast was grown in Yeast Extract Peptone Dextrose (YPD) medium. Various pretreatment techniques, hydrolysis methods, and fermentation parameters were assessed to enhance ethanol yield. Results: Arhar stem (Cajanus cajan) were found to contain ~40% cellulose, 25% hemicellulose and 20% lignin. Using optimized acid/enzymatic pretreatment and S. cerevisiae fermentation, we achieved 70 g/L ethanol (85% of the theoretical maximum), equivalent to 0.45 g ethanol per gram of dry biomass. Conclusion: The study found that with suitable processing techniques, Arhar stem (Cajanus cajan) can be effectively converted into fermentable sugars. Optimization of pretreatment and fermentation conditions led to improved bioethanol yields, highlighting the stem’s viability as a bioethanol feedstock.