Effects of Glucose Concentration on Ethanol Fermentation of White-Rot Fungus Phanerochaete sordida YK-624 Under Aerobic Conditions

Ethanol fermentation by saprotrophic white-rot fungus Phanerochaete sordida YK-624 during wood decay as a system for short-term resistance to hypoxic conditions

In this study, major factors involved in regulating ethanol production from wood by the saprotrophic white-rot fungus Phanerochaete sordida YK-624 were investigated. P. sordida YK-624 produced ethanol from wood meal culture without the addition of any nutrients, and ethanol was produced from wood culture only when the oxygen concentration in headspace was reduced to ≤5%; thereafter, ethanol production ceased within a few days. Analyses of gene expression during aerobic incubation indicated that P. sordida simultaneously upregulates the glycolytic pathway from sugar uptake to pyruvate conversion during ethanol fermentation and suppresses pyruvate influx into the TCA cycle. Upon termination of ethanol fermentation, the expression of all tested genes was repressed, and the fungus ceased to grow. In contrast, the fungus could utilize ethanol for aerobic growth. These results suggest that ethanol fermentation by P. sordida functions as a short-term stress response system under anaerobic conditions during wood decay, enabling the fungus to rapidly resume growing when oxygen is supplied (e.g., following breakdown of plant cell walls or removal of the fungus from water immersion). This is the first report to describe the physiologic significance of ethanol fermentation in saprotrophic white-rot fungi.

Studies on the characteristics and mechanism of aerobic biodegradation of tetrabromobisphenol A by Irpex lacteus F17

The study investigated the characteristics of aerobic degradation of tetrabromobisphenol A (TBBPA) by Irpex lacteus F17 (I. lacteus F17) under four different cometabolic substrates (phenol, glucose, sodium pyruvate, and sodium citrate). The biodegradation of TBBPA by I. lacteus F17 could be enhanced via cometabolism, and glucose (8 g/L) was confirmed to be the optimum carbon source. For different initial solution pH ranging from 3.0 to 8.0, the results showed that I. lacteus F17 could be applied to biodegrade TBBPA in a wide pH range of 4.0-8.0, and the degradation rate could reach the maximum 75.31%, while the debromination rate reached the maximum 12.40% under pH 5.0. In addition, it has been confirmed that Mn²⁺ (50 μmol/L) could promote the secretion of manganese peroxidase and TBBPA biodegradation efficiency. Seven intermediates were identified by gas chromatography-mass spectrometry analysis, and the possible degradation pathways were proposed, which indicated the biodegradation of TBBPA might be subjected to debromination, β-scission, hydroxylation, deprotonation, and oxidation reactions.