Abstract
Various agricultural products used in food fermentation are polluted by heavy metals, especially copper, which seriously endangers human health. Methods to remove copper with microbial strategies have gained interests. A novel Meyerozyma guilliermondii GXDK6 could survive independently under high stress of copper (1400 ppm). The copper tolerance mechanism of GXDK6 was revealed by integrated omics in this work. Whole-genome analysis showed that nine genes (i.e., CCC2, CTR3, FRE2, GGT, GST, CAT, SOD2, PXMP4, and HSP82) were related to GXDK6 copper tolerance. Copper stress elevated glutathione metabolism-related gene expression, glutathione content, and glutathione sulfur transferase activity, suggesting enhanced copper conjugation and detoxification in cells. The inhibited copper uptake by Ctr3 and enhanced copper efflux by Ccc2 contributed to the decrease in intracellular copper concentration. The improved expression of antioxidant enzyme genes (PXMP4, SOD2, and CAT), accompanied by the enhanced activities of antioxidant enzymes (peroxidase, superoxide dismutase, and catalase), decreased copper-induced reactive oxygen species production, protein carbonylation, lipid peroxidation, and cell death. The metabolite D-mannose against harsh stress conditions was beneficial to improving copper tolerance. This study contributed to understanding the copper tolerance mechanism of M. guilliermondii and its application in removing copper during fermentation.
Highlights
Copper is an essential trace element for living cells (Bao et al, 2020)
Yeast cells were grown in Yeast Extract Peptone Dextrose Medium (YPD) containing 2% glucose, 2% peptone, and 1% yeast extracts sterilized at 115◦C for 15 min
In the Cu-600 group, GXDK6 cells dented in the middle and became long
Summary
Copper is an essential trace element for living cells (Bao et al, 2020). Adults need to consume 1.2 mg copper daily for life activities (de Luna et al, 2020), and insufficient copper intake may cause anemia, gastrointestinal discomfort, and eye diseases (Zhang et al, 2019). The soil concentration of heavy metals in China is higher than in those in Europe and the United States but lower than those in India and Africa. This phenomenon may be due to the different levels of industrialization in different countries. On April 17, 2014, the first batch of national soil pollution survey results showed that one-fifth of the agricultural land was polluted by heavy metals. Heavy metal pollution has brought huge economic losses to our country. Excess copper cannot be metabolized and flows to the ecosystem, causing huge economic losses and copper accumulation in the food chain; as a result, many agricultural products are contaminated with copper. Food safety and human health have become a major issue worldwide (McLaughlin et al, 2000; Ling et al, 2007)
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