Degradation Mechanism of 2,4-Dichlorophenol by Fungi Isolated from Marine Invertebrates

Microbial degradation of organochlorine pesticide: 2,4-Dichlorophenoxyacetic acid by axenic and mixed consortium

The presence of 2,4-dichlorophenoxyacetic acid (2,4-D), an organochlorine herbicide, in the environment has raised public concern as it poses hazard to both humans and the ecosystem. Three potential strains having the capability to degrade 2,4-D were isolated from on site agricultural soil and identified as Arthrobacter sp. SVMIICT25, Sphingomonas sp. SVMIICT11 and Stenotrophomonas sp. SVMIICT13. Over 12 days of incubation, 81-90% of 100 mg/L of 2,4-D degradation was observed at 2% inoculum. A shorter lag phase with 80% of degradation efficiency was observed within 5 days when the inoculum size was increased to 10%. Six microbial consortia were prepared by combining the isolates along with in-house strains, Bacillus sp. and Pseudomonas sp. Consortia R3 (Arthrobacter sp. + Sphingomonas sp.), operated with 10% of inoculum, showed 85-90% degradation within 4 days and 98-100% in 9 days. Further, targeted exo-metabolite analysis confirmed the presence and catabolism of intermediate 2,4-dichlorophenol and 4-chlorophenol compounds.

Marine-derived fungi as biocatalysts

Marine microorganisms account for over 90% of ocean biomass and their diversity is believed to be the result of their ability to adapt to extreme conditions of the marine environment. Biotransformations are used to produce a wide range of high-added value materials, and marine-derived fungi have proven to be a source of new enzymes, even for activities not previously discovered. This review focuses on biotransformations by fungi from marine environments, including bioremediation, from the standpoint of the chemical structure of the substrate, and covers up to September 2022.

Degradation characteristics of crude oil by a consortium of bacteria in the existence of chlorophenol

In order to enhance the degradation effect of microorganisms on crude oil in the existence of chlorophenol compounds, oil-degrading bacteria C4 (Alcaligenes faecails), C5 (Bacillus sp.) and 2,4-dichlorophenol (2,4-DCP) degrading bacteria L3 (Bacillus marisflavi), L4 (Bacillus aquimaris) were isolated to construct a highly efficient consortium named (C4C5 + L3L4). When the compound bacteria agent combination by V_C4: V_C5: V_L3: V_L4 = 1:2:2:1, the crude oil degradation efficiency of 7 days was stable at 50.63% ~ 55.43% under different conditions. Degradation mechanism was analyzed by FTIR, GC-MS and IC technology and the following conclusions showed that in the system of adding consortium (C4C5 + L3L4), the heavy components were converted into saturated and unsaturated components. The bacterial consortium could first degrade medium and long chain alkanes into short chain hydrocarbons and then further degrade. And the dechlorination efficiency of 2,4-DCP in the degradation system reached 73.83%. The results suggested that the potential applicability and effectiveness of the selected bacteria consortium for the remediation of oil-contaminated water or soil with the existence of chlorophenol compound.

Degradation of 2,6-dicholorophenol by Trichoderma longibraciatum Isolated from an industrial Soil Sample in Dammam, Saudi Arabia

2,6-Dichlorophenol (2,6-DCP) is an aromatic compound with industrial importance in making insecticides, herbicides, and other organic compounds. However, it poses serious health and ecological problems. Microbial degradation of 2,6-DCP has been widely applied due to its effectiveness and eco-friendly characteristics. In this study, Trichoderma longibraciatum was isolated from an industrial soil sample in Dammam, Saudi Arabia using the enrichment method of mineral salt's medium (MSM) amended with 2,6-DCP. Morphological and molecular identification (using the internal transcribed spacer rRNA gene sequencing) of the 2,6-DCP tolerating fungal isolate were charactraized. The fungal isolate has demonstrated a tolerance to 2,6-DCP up to 300 mg/L. Mycelial growth and fungal sporulation were reduced with increasing 2,6-DCP concentrations up to 96 h incubation period. However, after 168 h incubation period, the fungal isolate recorded maximum growth at all the tested 2,6-DCP concentrations up to 150 mg/L. Carboxy methyl cellulase production by tested fungus was decreased by increasing 2,6-DCP concentration up to 75 mg/L. The biodegradation pattern of 2,6-DCP in GM liquid medium using GC–mass analysis as well as the degradation pathway was presented. This study provides a promising fungal isolate that could be used in the bioremediation process for chlorinated phenols in soil.

Recent developments in the biology and biotechnological applications of halotolerant yeasts

Natural hypersaline environments are inhabited by an abundance of prokaryotic and eukaryotic microorganisms capable of thriving under extreme saline conditions. Yeasts represent a substantial fraction of halotolerant eukaryotic microbiomes and are frequently isolated as food contaminants and from solar salterns. During the last years, a handful of new species has been discovered in moderate saline environments, including estuarine and deep-sea waters. Although Saccharomyces cerevisiae is considered the primary osmoadaptation model system for studies of hyperosmotic stress conditions, our increasing understanding of the physiology and molecular biology of halotolerant yeasts provides new insights into their distinct metabolic traits and provides novel and innovative opportunities for genome mining of biotechnologically relevant genes. Yeast species such as Debaryomyces hansenii, Zygosaccharomyces rouxii, Hortaea werneckii and Wallemia ichthyophaga show unique properties, which make them attractive for biotechnological applications. Select halotolerant yeasts are used in food processing and contribute to aromas and taste, while certain gene clusters are used in second generation biofuel production. Finally, both pharmaceutical and chemical industries benefit from applications of halotolerant yeasts as biocatalysts. This comprehensive review summarizes the most recent findings related to the biology of industrially-important halotolerant yeasts and provides a detailed and up-to-date description of modern halotolerant yeast-based biotechnological applications.

Functional and transcriptomic investigation of laccase activity in the presence of PCB29 identifies two novel enzymes and the multicopper oxidase repertoire of a marine-derived fungus

Polychlorinated biphenyls (PCBs) are persistent organic pollutants (POPs), that can be detected in a variety of environments including the human body, adversely affecting global health. Bioremediation is an emerging field for the detoxification and removal of environmental pollutants, with novel biocatalysts appropriate for this task being in high demand. In this study, a biobank of novel fungal strains isolated as symbionts of marine invertebrates was screened for their ability to remove 2,4,5-trichlorobiphenyl (PCB29). The most efficient strains were studied further for their ability to express laccase activity, the most commonly associated extracellular activity involved in the removal of aromatic pollutants and encoded in fungi by the enzymatic class of multicopper oxidases (MCOs). The strain expressing the highest laccase activity, Cladosporium sp. TM138-S3, was cultivated in the presence of copper ions in a 12 L bioreactor and two enzymes exhibiting laccase activity were isolated from the culture broth through ion-exchange chromatography. The two enzymes, Lac1 and Lac2, were biochemically characterized and showed similar characteristics, although an improved ability to remove PCB29 (up to 71.2%) was observed for Lac2 in the presence of mediators. In parallel, we performed RNAseq of the strain growing in presence and absence of PCB29 and reconstructed its transcriptome assembly. Functional annotation allowed identifying the MCO repertoire of the fungus, consisting of 13 enzymes. Phylogenetic analysis of Ascomycete MCOs further allowed classifying these enzymes, revealing the diversity of laccase activities in Cladosporium sp. TM138-S3.