Valorisation of composting spent leachate for sustainable microbial growth: enhancing biomass production of <i>Saccharomyces cerevisiae</i> MTCC 173

The composting of domestic food waste generates substantial amount of leachate with high organic load, which we previously utilised for bioethanol production. This study investigates the use of spent leachate from bioethanol production as a sustainable growth medium for Saccharomyces cerevisiae MTCC 173, aiming to create a zero-discharge system and enhance resource utilisation in bioethanol processes. The supernatant from the fermentation process, containing 12 % bioethanol, was distilled, and after 30 min, the distillate and spent leachate were collected. The spent leachate was then lyophilised, and the resulting nutrient-rich powder was used as a carbon source for S. cerevisiae MTCC 173 growth. FT-IR characterisation demonstrated similarities to yeast extract and peptone, suggesting its potential as a nutrient source. Growth experiments were conducted at the shake-flask level, testing spent leachate with and without yeast extract and peptone supplements. The results indicated that S. cerevisiae MTCC 173 grew effectively in the spent leachate, with enhanced growth observed in supplemented conditions. This study highlights the potential of spent leachate as a sustainable growth medium, aligning with the principles of a circular economy by reducing waste and optimising resource utilisation. By supporting S. cerevisiae MTCC 173 growth, this approach contributes to zero-discharge strategies and enhances the sustainability of bioethanol production. Additionally, it underscores the need for further research to explore the broader sustainability aspects of the process.