Evaluation of brewers’ spent grain as a novel media for yeast growth

Abstract

Brewers’ spent grain (BSG) is a by-product generated from the beer manufacturing industry, which is extremely rich in protein and fiber. Here we use low cost BSG as the raw material for the production of a novel growth media, through a bioconversion process utilizing a food grade fungi to hydrolyze BSG. The novel fermentation media was tested on the yeast Rhodosporidium toruloides, a natural yeast producing carotenoid. The yeast growth was analysed using the growth curve and the production of intracellular fatty acids and carotenoids. Untargeted GCMS based metabolomics was used to analyse the constituents of the different growth media, followed by multivariate data analysis. Growth media prepared using fermented BSG was found to be able to support the growth in R. toruloides (21.4 mg/ml) in comparable levels to YPD media (24.7 mg/ml). Therefore, the fermented BSG media was able to fulfill the requirement as a nitrogen source for R. toruloides growth. This media was able to sustain normal metabolomics activity in yeast, as indicated by the level of fatty acid and carotenoid production. This can be explained by the fact that, in the fermented BSG media metabolites and amino acids were found to be higher than in the unfermented media, and close to the levels in YPD media. Taken together, our study provided evidence of a growth media for yeast using BSG. This should have potential in replacing components in the current yeast culture media in a sustainable and cost effective manner.

Transforming okara into a microalgae culture medium

“…As such, fermentation may enhance the amount of small free amino nitrogen molecules and serve as an effective nitrogen source for cultivating P. tricornutum cells. A similar trend was found in a study (Cooray, Lee, & Chen, 2017) which fermented another type of food by-product, brewers' spent grain (BSG), a protein and fiber rich by-product produced from the beer manufacturing industry. The authors reported increased amino acid content in fermented BSG media compared to unfermented BSG media.…”

Valorization of brewer's spent grain using fermentation : potential for food sustainability

“…Relative production of carotenoids; torularhodin, torulene and β-carotene by R. toruloides when grown in YPD, Fermented BSG (2%w/w glucose) and Unfermented BSG (2%w/w glucose) media [230].…”

“…Growth curves for R. toruloides when grown in YPD, Unfermented BSG and Unfermented BSG (2%w/w glucose) media[230].…”

“…Growth curves for R. toruloides when grown in YPD, Fermented BSG and Fermented BSG (2%w/w glucose) media[230] Fatty acid and carotenoids production R. toruloides, being an oleaginous microorganism is reported to accumulate lipids.…”

“…Spectra observed by GC-MS of Unfermented BSG media (top), Fermented BSG media (middle) and YP media (bottom)[230].Metabolome of the YP, fermented BSG media and unfermented BSG media was examined to gain insight into their variation. The studies were established using GC-MS results and multivariate data analysis.…”