Enhanced production of violacein by Chromobacterium violaceum using agro-industrial waste soybean meal

The research is aimed at developing an economic and sustainable growth medium using abundantly available and highly nutritive agro-industrial waste soybean meal as the substrate for the production of violacein by Chromobacterium violaceum.

Violacein produced using soybean meal medium was compared with the commercial complex growth media. Upon utilization of 2% w/v soybean meal (SM₂ ) medium, 496 mg/L crude violacein was achieved after 48-hr incubation time, which was 1.62-fold higher than the crude violacein produced in Luria-Bertani (LB) broth. Additionally, supplementation of 100 mg/L L-tryptophan to 1% and 2% w/v soybean meal (SMT₁ and SMT₂ ) medium yielded 1217 mg/L (3.96-fold higher as compared to LB) and 1198 mg/L (3.90-fold higher as compared to LB) crude violacein respectively. Optimization of culture conditions and concentration of L-tryptophan using Box-Behnken design (BBD) model produced as high as 1504.5 mg/L crude violacein. To the best of our knowledge, this is the highest crude violacein produced to date using agro-industrial-based waste as a substrate with minimal supplementation in a shake flask.

The study signifies the potentiality of soybean meal as a cost-effective growth medium for the production of violacein. Optimization of the fermentation parameters clearly demonstrated a surge in violacein production.

Utilization of soybean meal as an alternative to the expensive commercial media would surely promote the large-scale synthesis of this multifaceted compound.