Submitted to: Biomass Conversion and Biorefinery
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/9/2020
Publication Date: 3/7/2020
Citation: Yegin, S., Saha, B.C., Kennedy, G.J., Berhow, M.A., Vermillion, K. 2020. Efficient bioconversion of waste bread into 2-keto-D-gluconic acid by Pseudomonas reptilivora NRRL B-6. Biomass Conversion and Biorefinery. 10(2):545-553. https://doi.org/10.1007/s13399-020-00656-7.
DOI: https://doi.org/10.1007/s13399-020-00656-7

Interpretive Summary: 2-keto-gluconic acid is a key component in manufacture of vitamin C and an important food preservative. To date, industrial production of this compound is being carried by fermentation using glucose as substrate. In this research, we have demonstrated that waste bread is an excellent medium for production of 2-keto-gluconic acid without adding nutrients such as nitrogen source and mineral salts. This is the first study on the production of 2-keto-gluconic acid from food waste and results will be very useful for industrial production of this compound from food waste.

Technical Abstract: Development of bioprocess routes for production of value added materials from food waste is very attractive in terms of bioprocess economics and environmental protection. In this study, production of 2-keto-D-gluconic acid, a significant platform chemical, from food waste was performed by Pseudomonas reptilivora NRRL B-6 for the first time. The nitrogen source preference of the strain for 2-keto-D-gluconic acid production under different glucose concentrations in synthetic medium has been elucidated. At higher glucose concentrations, utilization of organic nitrogen (yeast extract) source led to higher product formation while at lower glucose concentration, utilization of inorganic nitrogen source (ammonium chloride) was also very feasible. The results indicated that favorable nitrogen source for 2-keto-D-gluconic acid production can change depending on the glucose concentration. The waste bread hydrolysate (Glucose: 181.43 g/L, Protein: 1.21 % (w/v)) prepared by sequential application of a-amylase, amyloglucosidase and protease was utilized in medium formulation at different glucose concentrations. Bread hydrolysate without additional supplements provided higher product formation than the optimum medium prepared with the hydrolysate. Utilization of 50 g/L CaCO3 led the maximum product formation. The maximum 2-keto-D-gluconic acid production from waste bread was 142.81 g/L with the productivity of 3.02 g/L/h and molar yield of 0.95. The proposed approach in this study confirms that waste bread as a sole source of nutrients can be valorized for microbial production of various industrially relevant platform chemicals.