Gamma-linolenic acid production of Mucor rouxii by solid-state fermentation using agricultural by-products

Aims:  This study aims to maximize the yield of gamma-linolenic acid by a filamentous fungus, Mucor rouxii , using low cost production by solid-state fermentation.
Methods and Results:  We optimized substrate types and culture conditions including inoculum size and temperature. The optimal growth of M. rouxii was found in the cultures inoculated with 5 × 10⁵ spores g⁻¹ substrate. The fungal cells grew well on rice bran and soy bean meal, whereas a lower biomass was found in the cultures grown on polished rice, broken rice and spent malt grain. The GLA content was highly accumulated in rice bran ferment and its maximal content of about 6 g kg⁻¹ fermented mass was observed in the 5th-day culture grown at 30°C. However, the GLA content in the rice bran ferment was not enhanced by low temperature.
Conclusions:  The GLA production of M. rouxii could be enhanced by optimizing the agricultural by-product substrates and culture condition.
Significance and Impact of the Study:  Low cost GLA production process was achieved, and fermented product containing GLA can be incorporated into feed additives without further oil extraction to alternate the expensive plant oils.