Science and Technology

Magic bacteria that turns low-cost agri waste into industrial enzymes

Akshay Anantharaman | Updated on: May 11, 2022
Rice bran is a rich source of carbon and nitrogen

Rice bran is a rich source of carbon and nitrogen | Photo Credit: voshadhi

IIT-Madras team deploys bacteria isolated from sugar cane waste to design a cost-effective and sustainable process

Industrial enzymes such as alpha-amylase and cellulase are in high demand in the manufacture of textiles, paper, detergents, and pharmaceuticals. The market for such enzymes is expected to reach $1.27 billion by 2021.

Each year, nearly 100–150 million tonnes of biomass is produced. The international focus recently has been on the use of non-food lignocellulosic biomass to produce industrially important enzymes and second-generation cellulosic ethanol as an alternative fuel.

The three main residues from agricultural industries are wheat bran, sago waste, and rice bran.

These residues are inexpensive and contain abundant amounts of carbon and nitrogen sources. However, there are many problems involved in obtaining industrial enzymes from these residues.

The complex structure of these residues limits enzyme hydrolysis — namely, the breakdown of a compound in the presence of enzymes following the enzymes’ reaction with water — a process used extensively in the chemical industry. A large amount of enzymes is required to hydrolyse these rigid structures. The process is costly because pretreatment is required followed by hydrolysis with various enzymes.

Thus, the focus is on identifying a single microorganism that can produce multiple enzymes to solve these issues. Some bacteria are good candidates for this because they have rapid growth rates, shorter fermentation cycle, and the ability to secrete a significant amount of extracellular enzymes

A study by Rekha Rajesh and Prof Sathyanarayana N Gummadi of the Department of Biotechnology, IIT-Madras, attempted to evaluate the saccharification and fermentation capacity of a previously isolated organism to hydrolyse low-cost lignocellulosic wastes such as wheat bran, sago waste, and rice bran without pretreatment.

The bacteria used was Bacillus sp PM06, which they had isolated from sugar cane waste. When this isolate was grown in the presence of lignocellulosic biomass, starch and cellulose were broken down to yield alpha-amylase and cellulase enzymes. Ethanol and acetic acid were also produced, which are useful in various industries.

Because of the rapid fermentation, the hydrolysed products did not inhibit enzyme activity, thus making the process cost-effective and sustainable. There was also no need for additional processes such as pretreatment. Wheat bran was found to be the most promising substrate, followed by sago waste and rice bran. The study demonstrated simultaneous saccharification and fermentation of different agro-residues by a single novel Bacillus sp PM06. This research is unique because it takes a sustainable and environmentally friendly approach, producing renewable biofuels. Possible future research could be the use of Bacillus sp PM06 to produce ethanol on an industrial scale.

Prof Ashok Pandey from the Centre for Innovation and Translational Research, CSIR-Indian Institute of Toxicology Research, Lucknow, India, commented that the research showcases the feasibility of using agro-industrial residues as feedstock for bioprocess production of industrial enzymes, bioethanol and acetic acid. “Considering that India has a huge surplus of agro-industrial residues, which need a sustainable avenue for their utilisation, this study is of great relevance as it works on the principles of biomass-based biorefineries,” Pandey says.

The method offers potential benefits for energy and environmental sustainability. The ability of the culture to utilise low-cost agricultural byproducts to produce industrial important enzymes along with biofuel (bioethanol) and organic acid (acetic acid) could be of great relevance for industrial exploitation.

(This article first appeared in IIT-Madras' Tech Talk)

Published on May 08, 2022
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