Maize stover as a feedstock for enhanced laccase production by two gammaproteobacteria: A solution to agroindustrial waste stockpiling

Abstract

The production of grain crops, worldwide is traditionally tantamountto the generation of hardy plant crop residues, once their edible parts have been consumed. These residues could serve as agents of environmental pollution, when eventually burned. Conversely, it is widely reported that most agro-industrial residues are a repository of nutrients and compounds sufficient to support the growth of many microorganisms. Therefore, our goal in this current investigation was to valorize some agro-industrial wastes, with especial focus on maize stover for the production of laccase from two gammaproteobacteria (Stenotrophomonas maltophila BIJ16; Berl11b2 and Citrobacter freundii LLJ16; Ie1c). Production time line featured the classical optimization to screen out the significant fermentation factors, and the statistical approach, central composite design of response surface methodology, to detect the optimal levels of the significant variables identified in the aforementioned screening. As outcomes, the synchronous effect of classical and statistical optimization identified maize stover as a conceivable biomaterial for enhanced laccase production in both isolates reviewed. Maximum laccase outputs from practical evaluations were observed at model validations where predictions were stretched beyond limits of the design space (Berl11b2; 208.23 U/mL, Ie1c; 205.50 U/mL), yet the similarity with the experimental outcomes was considerably high (≥cca. 90%). The overall 27.2 and 20.93 fold increase in extracellularly secreted laccase titer therefore confirms RSM as a pivotal experimental tool in valorizing maize as an ideal feedstock for laccase production, and it should be employed beyond the laboratory scale for tremendous production of laccase.