Bacterial cellulase production via co-fermentation of paddy straw and Litchi waste and its stability assessment in the presence of Zn-Mg mixed-phase hydroxide-based nanocomposite derived from Litchi chinensis seeds

Co-fermentation via co-cultured bacterial microorganisms to develop enzymes in solid-state fermentation (SSF) is a promising approach. This strategy is imperative in a series of sustainable and effective approaches due to superior microbial growth and the use of a combination of inexpensive feedstocks for enzyme production wherein mutually participating enzyme-producing microbial communities are employed. Moreover, the addition of nanomaterials to this technique may aid in its prominent advantage of enhancing enzyme production. This strategy may be able to decrease the overall cost of the bioprocessing to produce enzymes by further implementing biogenic, route-derived nanomaterials as catalysts. Therefore, the present study attempts to explore endoglucanase (EG) production using a bacterial coculture system by employing two different bacterial strains, namely, Bacillus subtilis and Serratia marcescens under SSF in the presence of a Zn-Mg hydroxide-based nano-composite as a nanocatalyst. The nanocatalyst based on Zn-Mg hydroxide has been prepared via green synthesis using Litchi waste seed, while SSF for EG production has been conducted using cofermentation of litchi seed (Ls) and paddy straw (Ps) waste. Under an optimized substrate concentration ratio of 5:6 Ps:Ls and in the presence of 2.0 mg of nanocatalyst, the cocultured bacterial system produced 1.6 IU/mL of EG enzyme, which was similar to 1.33 fold higher as compared to the control. Additionally, the same enzyme showed its stability for 135 min in the presence of 1.0 mg of nanocatalyst at 38 degrees C. The nanocatalyst has been synthesized using the green method, wherein waste litchi seed is used as a reducing agent, and the nanocatalyst could be employed to improve the production and functional stability of crude enzymes. The findings of the present study may have significant application in lignocellulosic-based biorefinaries and cellulosic waste management.

Automated summary

Co-fermentation using co-cultured bacterial microorganisms is a promising technique for enzyme production in solid-state fermentation (SSF). The addition of nanomaterials, such as a Zn-Mg hydroxide-based nano-composite, can further enhance enzyme production. In this study, endoglucanase (EG) production was explored using a co-culture system of Bacillus subtilis and Serratia marcescens in SSF with the presence of a Zn-Mg hydroxide-based nanocatalyst. The optimized condition resulted in a 1.33-fold increase in EG enzyme production compared to the control, and the nanocatalyst showed stability for 135 minutes at 38 degrees C.