Bioconversion of Baijiu Huangshui for single cell protein using Saccharomyces cerevisiae: A study on influence of carbon metabolic pathways.

The study presented a novel approach to treating Huangshui, a typical organic wastewater from Chinese Baijiu industry, utilizing Saccharomyces cerevisiae (S. cerevisiae) to convert the carbon source from Huangshui into its cellular component, ultimately forming single cell protein (SCP). S. cerevisiae tended to use organic acids in Huangshui. Adjusting organic load could lower ammonia nitrogen, total organic carbon, total nitrogen and phosphorus from Huangshui, with their corresponding removals of 2.5 ± 0.15 %-39 ± 0.2 %, 21.34 ± 0.26 %-79.73 ± 2.3 %, 23.8 ± 0.16 %-87.86 ± 1.7 %, and 29.45 ± 0.15 %-62.78 ± 1.8 %, respectively. Optimal organic load (30 g/L) achieved remarkable SCP yield (5.83 ± 0.17 g/L) with 36.82 ± 3.02 % protein content. Transcriptomic analysis revealed that high organic loads (e.g., 260 g/L) caused the down-regulation of genes related to cell wall synthesis, including RHO1, CCW12 and CWP2, as well as genes associated with ribosome formation, such as RPL28, RPS21B, RPL18A and RPS4A. Carbon metabolic pathways including transformation of organic acids into acetyl-CoA and the tricarboxylic acid cycle were inhibited at 260 g/L. The expression of related genes like ACS1, IDP1 and LSC1 was down-regulated. This work demonstrated efficient organic load reduction coupled with high-quality SCP yield, offering a sustainable solution for Baijiu wastewater management.