Fermentation of Rice Straw Hydrolyzates for Bioethanol Production and Increasing its Yield by Applying Random Physical and Chemical Mutagenesis

The increase in rice straw production and their non-utilization is a major global challenge. Even though it is an eco-friendly feedstock for the bioconversion of energy production separation of cellulose from the rice straw fiber is one of the main limitations that obstruct the application of such lignocellulosic feedstock. In the present research work, acid-alkali pretreatment technologies were applied to the rice straw to increase enzymatic accessibility and improve cellulose digestibility. The rice straw was physically and chemically treated and the chemical pretreatment with 4% sodium hydroxide released a maximum cellulose of 120.33 mg/L. The constituents of cellulose, hemicellulose, and lignin were estimated while the functional groups were identified by using Infrared spectroscopy. Further, the morphological and structural characterization between the untreated and the treated rice straw were analyzed by Scanning Electron Micrograph (SEM) analysis which demonstrated a highly distorted structure in the pretreated biomass. Rice straw was used for the production of bioethanol, with simultaneous saccharification fermentation (SSF) yielding higher ethanol (21.77%) than separate hydrolysis fermentation (SHF) (11.65%) by using commercial enzymes and yeast isolates, and optimal production conditions were determined. Pre-treating rice straw with 4% NaOH, optimized enzyme concentration (2:1:1), and SSF with Saccharomyces cerevisiae or 72-hour incubation at pH 4 yielded the highest bioethanol production. mutagenesis using UV rays and chemicals like Ethidium Bromide (EtBr) and Ethyl Methane Sulfonate (EMS) improved bioethanol yield, with EMS treatment exhibiting the most significant increase i.e. with the wild strain (21.77%) and with the mutant strain (24.29%) was achieved. Such a strategy will be eco-friendly and effective for the reduction of biomass and the production of bioethanol at a much lower cost.