Feasibility and Sustainability of Bioethanol Production from Starchy restaurants’ Bio-wastes by New Yeast Strains

The study treats an important and imperious worldwide problem. It deals with the production of alternative biofuels from starchy restaurants’ bio-waste. The starchy wastes of the restaurants, especially in developing countries, are produced in huge quantities that represent a sustainable substrate for ethanol production. So, we aimed to study the feasibility of the conversion of the starchy wastes to biofuel (bioethanol) using different pretreatments and new yeast strains. Our results approved the feasibility of conversion of the starchy wastes into biofuel. Using of thermo-acidic hydrolysis, we obtained 360 g of free and fermentable sugars from each dry kg of the wasted materials. Pichia barkeri and Candida intermedia were introduced as new species for the field of biofuel production in addition to the classical Saccharomyces cerevisiae. Among them, S. cerevisiae KKUY-0301 produced 11.5 g/L of ethanol from 27 g of sugars. Its transformation rate was 82% of the theoretical yield, i.e. 1 kg of the waste could produce 150 g of ethanol. Optimization of the cultural conditions approved that 4 days of incubation, pH 5, 35 °C and 5% of the yeast inoculum (108 cell/mL) were the most appropriate conditions that could induce the maximum production bioethanol. This study recommends the application of this technology on a commercial scale all over the world to benefit from all types of bio-wastes. In addition, our findings offer a crucial solution for the recycling the restaurant starchy waste materials into ecofriendly product “biofuel” that reduce the overall cost production of the bioenergy and make it a competitive to the oil-based energy.