Optimization technology of the LHS-1 strain for degrading gallnut water extract and appraisal of benzene ring derivatives from fermented gallnut water extract pyrolysis by Py-GC/MS

Abstract

Gallnut water extract (GWE) enriches 80∼90% of gallnut tannic acid (TA). In order to study the biodegradation of GWE into gallic acid (GA), the LHS-1 strain, a variant of Aspergillus Niger, was chosen to determine the optimal degradation parameters for maximum production of GA by the response surface method. Pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) was first applied to appraise benzene ring derivatives of fermented GWE (FGWE) pyrolysis by comparison with the pyrolytic products of a tannic acid standard sample (TAS) and GWE. The results showed that optimum conditions were at 31 °C and pH of 5, with a 50-h incubation period and 0.1 ġL-1 of TA as substrate. The maximum yields of GA and tannase were 63∼65 mġmL-1 and 1.17 UmL-1, respectively. Over 20 kinds of compounds were identified as linear hydrocarbons and benzene ring derivatives based on GA and glucose. The key benzene ring derivatives were 3, 4, 5-trimethoxybenzoic acid methyl ester, 3-methoxy-1, 2-benzenediol, and 4-hydroxy-3, 5-dimethoxy-benzoic acid hydrazide.