Enzyme activities during Benzo[a]pyrene degradation by the fungus Lasiodiplodia theobromae isolated from a polluted soil

Huimin Cao,Hongwen Sun,Haibin Liu,Cuiping Wang,Weili Jia

doi:10.1038/s41598-020-57692-6

Abstract

The enzyme activities of the fungus Lasiodiplodia theobromae (L. theobromae) were studied during degradation of benzo[a]pyrene (BaP). The L. theobromae was isolated from a polycyclic aromatic hydrocarbons (PAHs) contaminated soil collected from the Beijing Coking Plant in China and can potentially use BaP as its sole carbon source with a degradation ratio of up to 53% over 10 days. The activities of lignin peroxidase (LiP) and laccase (LAC) could be detected during BaP biodegradation; while manganese peroxidase (MnP) was not detected. Both glucose and salicylic acid enhanced BaP biodegradation slightly. In contrast, the coexistence of phenanthrene (PHE) inhibited BaP degradation. These metabolic substrates all enhanced the secretion of LiP and LAC. The addition of Tween 80 (TW-80) enhanced BaP biodegradation as well as the LiP and LAC activities. At the same time, TW-80 was degraded by the L. theobromae. In addition, the L. theobromae was compared to Phanerochaete chrysosporium (P. chrysosporium), which is a widely studied fungus for degrading PAH. P. chrysosporium was unable to use BaP as its sole carbon source. The activities of LiP and LAC produced by the P. chrysosporium were less than those of the L. theobromae. Additionally, the four intermediates formed in the BaP biodegradation process were monitored using GC-MS analysis. Four metabolite concentrations first increased and then decreased or obtained the platform with prolonged BaP biodegradation time. Therefore, this study shows that the L. theobromae may be explored as a new strain for removing PAHs from the environment.

Highlights

Polycyclic aromatic hydrocarbons (PAHs) are a class of diverse organic compounds containing two or more fused aromatic rings of carbon and hydrogen atoms, which can be adsorbed into soil due to their highly hydrophobic, stability and strong recalcitrant nature, and its toxicity, mutagenicity and carcinogenicity present a significant threat to human health[1]
It was reported that lignin peroxidises (LiP) and manganese peroxidases (MnP) can directly catalyze the one-electron oxidation of polycyclic aromatic hydrocarbons (PAHs) with an ionization potential (IP) of up to 7.55 eV to produce PAH quinones[13,14], which can be further metabolized via ring fission[15]
A novel fungus that can use BaP as sole carbon was isolated from a PAH contaminated soil sample in the Beijing Coking Plant in Beijing, China by our research group, which was identified as the Lasiodiplodia theobromae (L. theobromae)[17]

Summary

Introduction

Polycyclic aromatic hydrocarbons (PAHs) are a class of diverse organic compounds containing two or more fused aromatic rings of carbon and hydrogen atoms, which can be adsorbed into soil due to their highly hydrophobic, stability and strong recalcitrant nature, and its toxicity, mutagenicity and carcinogenicity present a significant threat to human health[1]. A novel fungus that can use BaP as sole carbon was isolated from a PAH contaminated soil sample in the Beijing Coking Plant in Beijing, China by our research group, which was identified as the Lasiodiplodia theobromae (L. theobromae)[17]. This fungu belongs to the group of botryosphaeriaceous fungi, is a causal agent of storage rot in many fruits and tubers and is a serious pathogen for many agricultural and horticultural crops[18]. BaP was used as the sole carbon and energy source for the L. theobromae and ligninolytic enzymes produced during the BaP biodegradation were assessed. To confirm the potential of the L. theobromae as an efficient BaP degrader, a comparative study of BaP degradation and enzymatic activities was conducted between the L. theobromae and a well-known PAH-degrading fungus, P. chrysosporium

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