In the production of textiles, paper, detergents, and pharmaceuticals, industrial enzymes such as alpha-amylase and cellulase are in high demand. By 2021, the market for these enzymes is expected to reach $1.27 billion. Nearly 100–150 million tonnes of biomass are produced each year.
The use of non-food lignocellulosic biomass to produce industrially important enzymes and second-generation cellulosic ethanol as an alternative fuel has recently gained international attention. Wheat bran, sago waste, and rice bran are the three most common agricultural residues.
These residues are cheap and contain a lot of carbon and nitrogen sources. However, obtaining industrial enzymes from these residues poses numerous challenges.
The complex structure of these residues restricts enzyme hydrolysis — the breakdown of a compound in the presence of enzymes after the enzymes' reaction with water — a process widely used in the chemical industry. To hydrolyze these rigid structures, a large number of enzymes are required. Because pre-treatment is required before hydrolysis with various enzymes, the process is expensive.
To address these issues, researchers are looking for a single microorganism that can produce multiple enzymes. Some bacteria are good candidates for this because they grow quickly, have a shorter fermentation cycle, and can secrete a large number of extracellular enzymes.
Rekha Rajesh and Prof Sathyanarayana N Gummadi of IIT-Madras' Department of Biotechnology attempted to assess the saccharification and fermentation capacity of a previously isolated organism to hydrolyze low-cost lignocellulosic wastes like wheat bran, sago waste, and rice bran without pre-treatment.
Bacillus sp PM06 was used, which they isolated from sugar cane waste. When this organism was grown in the presence of lignocellulosic biomass, starch and cellulose were broken down, resulting in the production of alpha-amylase and cellulase enzymes. Ethanol and acetic acid were also produced, both of which have applications in a variety of industries.
The hydrolyzed products did not inhibit enzyme activity due to the rapid fermentation, making the process cost-effective and sustainable. Additionally, no additional processes, such as pre-treatment, were required. The most promising substrate was discovered to be wheat bran, followed by sago waste and rice bran. The study demonstrated that a single novel Bacillus sp PM06 can simultaneously saccharify and ferment various agro-residues.
This study is unique in that it produces renewable biofuels in a sustainable and environmentally friendly manner. Future research could look into using Bacillus sp PM06 to produce ethanol on a large scale.
Prof Ashok Pandey of the CSIR-Indian Institute of Toxicology Research, Lucknow, India, commented that the study demonstrates the feasibility of using agro-industrial residues as feedstock for bioprocess production of industrial enzymes, bioethanol, and acetic acid. "Given that India has a huge surplus of agro-industrial residues that require a sustainable avenue for their utilization," Pandey says, "this study is of great relevance as it works on the principles of biomass-based biorefineries."
