Effects of thermophilic and acidophilic microbial consortia on maize steeping

Abstract To understand the ecology of species and promote biotechnology through beneficial strain selection for improving starch yield in maize wet-milling steeping, bacterial diversity and community structure during the counter-current steeping process in a commercial steeping system were characterized and investigated in this study. Microbial diversity in the steeping liquor, which consisted of 16 phyla, 131 families, and 290 genera, was more abundant compared to those present on the surface of unsteeped maize. As the process of counter-current steeping progressed, with the newest maize being exposed to the oldest steepwater, Lactobacillus became the primary family, replacing Rahnella, Pseudomonas, Pantoea, and Serratia. The thermophilic and acidophilic microbial consortia were enriched through adaptive evolution engineering and employed to improve starch yield. Several steeping strategies were evaluased, including water alone, SO2 alone, mono-culture of B. coagulans, microbial consortia, and a combination of consortium and SO2. The combination of microbial consortium and SO2 resulted in a significant increase in starch yield, reaching approximately 66.4±0.5%, which was an increase of 22% and 46% compared to SO2 alone and microbial consortium alone, respectively. Additionally, protein solubilization was enhanced. Scanning electron microscope (SEM) of steeped maize structure indicated that the combination of consortium and SO2 disrupted the protein matrix and increased the gap between starch granules in maize endosperm. This led to the release of protein into the steepwater and the presence of starch granules in the aleurone layer. The steeping strategy of thermophilic and acidophilic microbial consortium as additives shows potential application as an environmentally friendly alternative for conventional procedures of maize steeping.