Biotransformation of wheat straw into biovanillin by solid-state fermentation and optimization of conditions parameters through response surface methodology

Vanillin is an organoleptic component of vanilla and is found in plants as a secondary metabolite. It has a wide range of applications in the food, feed, beverages and pharmaceutical industry. The plant-derived vanillin is expensive while chemically synthesized is not considered safe and natural according to the US and European regulations. Biovanillin, produced through microbial fermentation, is considered natural but the main problem is the cost of the substrate (ferulic acid) used for production. The current research was conducted with the aim to utilize a wheat straw, as a source of ferulic acid for biovanillin synthesis using Streptomyces sannanensis through solid-state fermentation. Five cultural parameters were optimized by using response surface methodology (RSM) for higher biovanillin production. The highest production (2.74 mg/g) was observed at 70 % moisture content, 72-h incubation time, 2-mL inoculum volume, 7.5 pH and 35 degrees C temperature. According to the results, the effect of incubation time, inoculum size, pH and temperature was significant (p-value < 0.05) on biovanillin production, while the moisture content had an insignificant effect. The F-value of the proposed model was 7.95, p-value was 0.001 and R-2 (coefficient of determination) was 93.53% which demonstrates the proposed model is significant. The FTIR spectrum concluded that the produced compound is biovanillin while it is found through HPLC to be 97.43% pure in comparison with the standard of Sigma-Aldrich. The solid-state fermentation for the production of biovanillin from wheat straw has proved to be a cost-efficient process. The outcome of the study can be used at a pilot scale for the commercial production of biovanillin.