Microbial conversion of pomegranate peels to biovanillin using submerged fermentation and process optimization through statistical design

Vanillin is the secondary metabolite in vanilla plants that acts as an aroma and flavoring agent. Natural vanillin, extracted from cured beans of vanilla, contributes only 0.2% to industrial demand. The remaining part is fulfilled by vanillin produced through chemical synthesis and microbial fermentation. The main substrate for vanillin biosynthesis, i.e., ferulic acid, is expensive. So, the present experimental study was intended to assess the potential of pomegranate peels as a source of ferulic acid for biotransformation into biovanillin using Enterobacter hormaechei via submerged fermentation. Different process parameters (e.g., ferulic acid concentration, incubation period, pH, temperature, and agitation speed) were optimized and their effect on biovanillin production was examined using central composite design (CCD) of response surface methodology (RSM). Approximately, 162.5 +/- 0.35 mg of ferulic acid was obtained from 100 g of pomegranate peels. The highest biovanillin production (4.2 g/L) was attained at 0.9% ferulic acid concentration, 8 h of incubation time, pH 7, temperature 30 degrees C, and agitation speed of 100 rpm. The F-value of 7.70 and p-value of 0.001 were calculated using a statistical tool that verified the utmost significance of the model. The 93.34% coefficient of determination (R-2) confirmed the precision of the designed model stating the effect of incubation time, temperature, pH, and agitation speed as significant on production yield. Identification of produced vanillin was determined by FTIR while HPLC indicates that produced biovanillin was 98.6% pure compared to the standard of Sigma-Aldrich. So, pomegranate peels served as an economical substrate for biotransformation into biovanillin. The optimized fermentation conditions could be further utilized for larger-scale production and value addition to market the product.