Maximizing Fungal Growth in State-of-the-Art Tray Solid-State Fermenter: Aeration Strategies Optimized for Enhanced Performance

Abstract

This study introduced a tray fermenter, featuring eight layers of squared perforated trays, specifically designed for solid-state fermentation applications. It is named the multi-layer squared tray solid-state fermenter. The fermenter employs two aeration strategies with varying air flow rates to optimize fungal growth. Firstly, sterilized moistened air at 8 L/min flows from the bottom through the perforated trays. Secondly, a flow rate of 1 L/min delivers sterilized moistened air directly onto the substrate surface. Real-time monitoring of fungal growth is enabled by an oxygen/carbon dioxide gas analyzer and a thermocouple, tracking oxygen consumption, carbon dioxide production and metabolic heat generation. Aspergillus awamori and Aspergillus oryzae thrive on wheat bran substrate within this fermenter. Carbon dioxide evolution, indicative of fungal activity, is modeled using a Gompertz model, showing strong agreement and fitting well with experimental data. The respiratory quotient, calculated from carbon dioxide evolution and oxygen uptake rates, confirms fungal activity levels. Additionally, the correlation between fungal metabolic heat generation and carbon dioxide evolution offers complementary insights into growth dynamics. Aeration strategies notably affected fungal productivity. Both A. awamori and A. oryzae showed higher spore production with moistened air at 1 L/min. A. awamori exhibits strong enzyme production, particularly glucoamylase, xylanase and cellulase, while A. oryzae, excelled in protease production under similar conditions. Continuous monitoring of environmental variables ensures precise control of fermentation conditions. These initial findings highlight the potential of the multi-layer squared tray solid-state fermenter, with its forced moistened aeration, as a promising instrument for solid-state fermentation processes.