Microbial Approach for Biofuel Production by Biomass Conversion

The continuous rise in demand for energy and the release of carbon dioxide (CO₂) due to the extensive use of fossil fuels has created a massive global crisis. The prime sources of nonrenewable energy are depleting day by day. According to the global statistical review released in the year 2021, primary energy demand has increased by 5.8%, which emphasizes the need for alternative sources of fuel due to the exhaustion of petroleum-derived fuels. Hence, biofuel can be a promising alternative feasible source of renewable energy that shows less emission of carbon and greenhouse gases (GHGs). This chapter gives an elaborate account on microbe-mediated biofuel production. Various bacteria such as Bacillus licheniformis, Bacillus pumilus, Bacillus subtilis, Bacillus thuringiensis, Clostridium acetobutylicum, Ensifer adhaerens, Pseudomonas aeruginosa, Pseudomonas geniculata, Sinomicrobium oceani, Sinomicrobium oceani, and Streptomyces fulvissimus can produce biofuels from diverse type of substrates. Likewise, fungi such as Aspergillus niger, Aspergillus oryzae, Aspergillus tubingensis, Candida tropicalis, Pecoramyces ruminantium, Periconia sp., Rhodotorula mucilaginosa, Saccharomyces cerevisiae, Trichoderma reesei, Trichosporonoides spathulata, and Yarrowia lipolytica, with high linoleic, linolenic, oleic, palmitic, palmitoleic, and stearic acid content, are superior biofuel producers. Photosynthetic microbes such as algae including Chlorella kessleri, Chlorella vulgaris, Chlorococcum sp., and Nannochloropsis oculata can convert specific substrates into biofuel. The underlying mechanism for production of biofuel is speculated to be the key involvement of the specific enzymes such as amylase, carboxymethyl cellulase, pectinase, thermotolerant β-glucosidase, and xylanase. Attempts are being made to develop genetically engineered recombinant microbes with high biofuel-producing capability. Further optimization of the process parameters and scale-up strategies are required to introduce biofuel as an alternative to conventional fossil fuel.