Study Of Growth Characteristics And Metabolic Mechanism Of Furan Gegradation By The Biodetoxification Fungus Amorphotheca Resinae ZN1

The degradation products from lignocellulose pretreatment strongly inhibit the activities of cellulase enzymes and ethanol fermentation strains, thus the efficient removal of the inhibitor substances ("detoxification") is the inevitable step for the biotransformation processes. Among the inhibitor substances, the furan derivatives including furfural and 5-hydromethylfurfural (5-HMF) are the major inhibitors. In this study, the biological detoxification of furfural and 5-HMF by a newly isolated fungus. Amorphotheca resinae ZN1, was studied and the metabolic pathways of furfural and 5-HMF were analyzed experimentally. This paper reported that A. resinae ZN1 can use much carbon source, and studied each carbon source for the biological virus-free fungi A. resinae ZN1 growth stimulative effect. Research found that the degradation products(including furan derivatives, organic acid and some aromatic compounds) from lignocellulose pretreatment can be as carbon sources for the growth of A. resinae ZN1. The metabolic pathways of furfural and 5-hydromethylfurfural were analyzed by means of fermentation tank on-line monitoring, regular sampling and high performance liquid chromatography (HPLC) quantitatively. The metabolic pathway of furfural and 5-HMF degradation in A resinae ZN1 was described as follows:first, furfural was quickly transformed into the low toxic furfuryl alcohol; then the furfuryl alcohol was gradually transformed into the furfural again but at the low concentration at aerobic condition, which was not lethal to the growth of the microorganisms; furfural continued to be oxidized to furoic acid by A. resinae ZN1. Similarly,5-HMF was quickly transformed into the furan-2,5-dimethanol (HMF alcohol); then the HMF alcohol was transformed into 5-HMF but at a low concentration at aerobic condition; followed by the transformation of 5-HMF to 5-hydroxylmethyl-furan-2-carboxylic acid. It is estimated that furoic acid and 5-hydroxylmethyl-furan-2-carboxylic acid were further degraded in the TCA cycle to complete the biological degradation of furfural and 5-HMF. The degradation was found to be closely related to the oxygen dissolution level. The present study provided the important experimental basis for speeding up the biodetoxification of furfural and 5-HMF by A. resinae ZN1 and the rate-limiting step in the lignocellulose biotransformation to ethanol.