Nano-Enzymatic Hydrolysis and Fermentation of Waste Starch Sources for Bioethanol Production: An Optimization Study

Abstract

With the inevitable depletion of the world’s energy supply and the rising pollution issues, there has been an increasing worldwide interest in alternative energy sources. One of the best options to beat this energy crisis is biofuel. Bio-ethanol is the best biofuel that can be produced by simply converting the sugar content of any starchy material into alcohol with the evolution of CO ₂ under controlled environmental conditions. More quantitative ethanol production can be carried out using a hydrolyzed starchy source. The hydrolysis of the starch is achieved through various methods, viz. acid hydrolysis, heat treatment, and enzymatic treatment, out of which the enzymatic method of hydrolysis shows prevalence. In the present study, the hydrolysis of starch sources is carried out by a nano-enzyme bio-conjugate. The enzyme used is α-amylase in association with silver nanoparticles. Previous studies indicate the efficacy of nano-enzymatic bio-conjugate, i.e., silver nanoparticles in association with á-amylase, showed a 2-fold increase in its efficacy in reaction mixtures over converting the substrates to products. Thus the usage of the catalys, silver nanoparticles-α-amylase bio-conjugate in the reaction mixture enhances the reaction rate in hydrolyzing the starch sources, thereby, more breakdowns of the sources be enabled in lesser time. The waste starch sources used in the current study are corn waste, rice husk, and potato peels which can reduce the economy of biofuel production. In this study, pretreatment of waste starch sources for hydrolysis was carried out using nano-enzyme bio-conjugate. Further to this, the efficacy of the hydrolyzed starch source in producing bioethanol was assessed in comparison with the non-hydrolyzed starch source when subjected to fermentation of hydrolyzed and non-hydrolyzed sources using baker’s yeast for 16hrs. The percentage of ethanol produced from hydrolyzed and non-hydrolyzed sources is estimated by gas chromatography. The factors affecting the bioethanol production are estimated by optimizing various ethanol process parameters, viz. time, pH, temperature, concentrate of starch source, and biomass concentration by the yield of bio-ethanol produced. The maximum percentage of bioethanol produced using hydrolyzed starch sources using nano-enzyme catalyst under the optimized condition is 63% in comparison with non-hydrolyzed sources, which was 13%.