Production of Rhizopus oryzae by solid state fermentation and evaluation of its biocomposite characteristics

Rhizophus oryzae biomass (RB) can be incorporated into polylactic acid (PLA) to create improved biocomposites that perfectly fit the biobased circular economy model. In this study, Rhizopus oryzae EGE-F75, produced through solid-state fermentation in aluminum trays with the maximum RB production conditions (Initial moisture (%): 79.84%, Inoculum ratio (%): 28.01, Incubation time (days): 9.74) was used as reinforcement material in PLA biocomposites. Biocomposites were obtained by adding varying amounts of RB (5% and 10% by weight) to PLA using a twin screw extruder, and the physical, thermal, mechanical and morphological properties of the biocomposites were investigated. According to the results, the incorporation of RB resulted in a decrease in mechanical properties. The tensile strength of 10% RB/PLA composite decreased by 23%, while the flexural modulus value of the composite increased by 6% compared to PLA. Furthermore, the addition of RB to PLA delayed the thermal decomposition of PLA and reduced its thermal conductivity. Introducing 5 wt% of RB to the PLA matrix reduced the thermal conductivity of the PLA matrix by 79%. Therefore, RB may not serve as an ideal filler for enhancing the mechanical properties and thermal stability of biocomposites, but it does offer potential as an alternative material for thermal insulation.