Starved Spirodela polyrhiza and Saccharomyces cerevisiae: a potent combination for sustainable bioethanol production

Abstract

The depletion of nonrenewable fossil fuels and the rise in their prices depicts that there is a need to fend for alternative fuel resources. Biofuels are one of these renewable alternative options. Among biofuels, bioethanol is one of the most widely used transportation fuels around the world. However, currently, bioethanol is produced from food crops, which is raising food versus fuel feud. Spirodela polyrhiza is one of the novel feedstock that can be used to produce bioethanol at large scale without causing any food and fuel competition. This study involves the collection of S. polyrhiza from a local pond and establishment of its growth in Hoagland growth media. The plant was then given nutrient starvation stress to enhance its starch content by 78%. The high-starch-containing plant biomass was acid-pretreated, and 99.3% starch-to-glucose conversion was achieved. In order to ferment plant sugars, yeast strain Saccharomyces cerevisiae QG1 MK788210 was indigenously isolated and statistically optimized using Plackett–Burman and central composite design to achieve high ethanol yield. The fermentation of plant sugar by Saccharomyces cerevisiae QG1 MK788210 resulted in 100% ethanol yield thus successfully achieving complete conversion of S. polyrhiza starch to bioethanol. The study conducted demonstrates effective optimization of indigenously isolated yeast strain S. cerevisiae QG1 MK788210 to deliver high ethanol yield from S. polyrhiza. Further, this study has been successful in delivering a process for complete conversion of starch from nutrient-starved S. polyrhiza biomass into bioethanol.