Sustainable and cost-effective production of glutamic acid by Corynebacterium glutamicum PTCC 1532 from waste bread using enzymatic hydrolysis and microbial fermentation
Document Type : Original research
Authors
Bioprocess Engineering Laboratory (BPEL), Department of Food Science, Engineering & Technology, Faculty of Agricultural Engineering and Technology, University of Tehran, P.O. Box 4111, Karaj 31587-77871, Iran
Abstract
Food waste generation has increased in recent years due to population growth. The continuous rise in food production for human consumption has resulted in 1.3 billion tons of food waste annually worldwide. Waste bread, an inexpensive substrate with high carbohydrate content, can hydrolyze by proper methods, such as enzymatic hydrolysis, for utilization in fermentation. Glutamic acid, a non-essential amino acid with various applications in pharmaceuticals, food industries, and cosmetics, can be produced by fermentation. In this study, we applied waste bread, as a cost-effective starchy waste, to produce fermentable substances through enzymatic hydrolysis. This process resulted in a significant increase in reducing sugar concentration from 1.285 ± 0.195 g/L to 123.282 ± 0.924 g/L. The obtained hydrolysate was utilized as a carbonic source for the glutamic acid synthesis by Corynebacterium glutamicum PTCC 1532. To enhance the glutamic acid yield, response surface methodology was employed to optimize the independent variables. The optimum levels of reducing sugar concentration of hydrolysate, urea concentration, biotin concentration, and inoculum size was 49.889 g/L, 6.812 g/L, 6.57 μg/L, and 5.339% (v/v), respectively. Under these optimized conditions, the experimental glutamic acid production was 21.34 ± 0.204 g/L, which demonstrated a reasonable correlation between the predicted and experimental results. This study illustrated that waste bread can serve as a low-cost carbon source for producing valuable compounds such as glutamic acid.
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