Study of the Influence of Substrates on Kojic Acid Production by Estuarine Aspergillus oryzae RMS2 Isolate Under Solid State Fermentation Using Sugar Cane Bagasse as an Inert Substrate

Aims: In the present study, sugarcane bagasse was evaluated as an inert support for the production of kojic acid under solid state fermentation using two different production medium as moistening agents for the maximum production of kojic acid. Different parameters such as fermentation time, carrier size, moisture content, pH, temperature and inoculum size were optimized using One-Factor-at-a-Time approach (OFAT).

Study Design: Two fermentation mixed media were designed with 1:6:3 concentrations, where 1% is carrier, 6% carbon substrate and 3% nitrogen substrate. Such as medium I containing (g/100 g) sugar cane bagasse (carrier), 10; rice bran (carbon substrate), 60; ground nut oil cake (nitrogen substrate) 30; KH2PO4, 0.2; MgSO4.7H2O, 0.05; NaCl, 0.25. Medium II containing (g/100 g) sugar cane bagasse (carrier), 10; tea waste (carbon substrate), 60; sunflower oil cake (nitrogen substrate), 30; KH2PO4, 0.2; MgSO4.7H2O, 0.05; NaCl, 0.25.

Place and Duration of Study: Sample: Soil samples were collected from Vellar Estuary, Portonovo (Lat. 11°29’ N; Long. 79°46’), South East coat of India, between January 2015 and July 2016.

Methodology: Soil samples were serially diluted and inoculated in to a Potato Dextrose agar plate (Hi-media) supplemented with 0.10 g of FeCl3 and incubated for 7 days at 35±2°C when the kojic acid producer strain was grown on the medium then the kojic acid reacts with ferric ions the color of the medium turned red at around 1 week. It was observed on reverse side of petri plate. Kojic acid estimated according to colorimetric method of Bently (1957).

Results: It was observed that sugarcane bagasse impregnated with medium I, pH 5.0, Temperature 30°C. at 80% moisture content (v/w), carrier size 0.5 mm and inoculum size of 30 ml/100 g support produced 109 g/kg of Kojic acid after 14 days as compared to 81 g/kg before optimization.

Conclusion: The combination of rich carbohydrates and rich protein substrates produced higher production (M1, 109 g/kg and M2, 106 g/kg) as compared to un-optimized conditions (81 g/kg and 79 g/kg, respectively). In addition, the yield (M1, 0.109 g/g substrate and M2, 0.106 g/g substrate) and productivity (M1, 0.324 g/kg.h and M2, 0.315 g/kg.h) obtained from the optimization was higher than that obtained from the un-optimized conditions (0.081 g/g substrate and 0.079 g/kg.h, respectively).