Abstract
Soybean whey wastewater (SWW), a rich source of soybean whey protein (SWP), is prone to microbial rancidity, posing environmental and resource challenges. This study explores the causes of rancidity-characterized by a pungent, sour, and putrid odor-in the effluents of sealed buffer tank during SWP recovery via pneumatic flotation. Metagenome, bacterial diversity, and HPLC analyses showed the obligate anaerobe Megasphaera spp. dominated rancid effluents (up to 44% abundance), consumed lactate (decreasing from 10.2 g/L in influent to 2.7 g/L in effluent), and produced malodorous propionate and butyrate (up to 3.6 and 4.3 g/L, respectively). Three mitigation strategies were assessed: (1) full-scale high-throughput aeration-likely effective but energy- and cost-intensive; (2) local aeration-low-cost but weakly inhibitory; and (3) microbial intervention using the probiotic Enterococcus faecium LBSW, which colonizes the buffer tank, with localized aeration used only if microbial control fails. Strategy (3) was adopted for its energy and cost efficiency, successfully reducing pollution and supporting SWP recovery. Although the biosafety of E. faecium LBSW in food applications requires caution, the recovered SWP is primarily intended for animal feed, and subsequent high-temperature drying and sterilization (> 120°C) also offer potential for food-grade use.