Studies on peroxidase production and detection of Sporotrichum thermophile-like catalase-peroxidase gene in a B acillus species isolated from Hogsback forest reserve, South Africa

Combined hemicellulolytic and phenoloxidase activities of Thermobacillus xylanilyticus enable growth on lignin-rich substrates and the release of phenolic molecules

Major challenge in biorefineries is the use of all lignocellulosic components, particularly lignins. In this study, Thermobacillus xylanilyliticus grew on kraft lignin, steam-exploded and native wheat straws produced different sets of phenoloxidases and xylanases, according to the substrate. After growth, limited lignin structural modifications, mainly accompanied by a decrease in phenolic acids was observed by Nuclear Magnetic Resonance spectroscopy. The depletion of p-coumaric acid, vanillin and p-hydroxybenzaldehyde combined to vanillin production in the culture media indicated that the bacterium can transform some phenolic compounds. Proteomic approaches allowed the identification of 29 to 33 different hemicellulases according to the substrates. Twenty oxidoreductases were differentially expressed between kraft lignin and steam-exploded wheat straw. These oxidoreductases may be involved in lignin and aromatic compound utilization and detoxification. This study highlights the potential value of Thermobacillus xylanilyticus and its enzymes in the simultaneous valorization of hemicellulose and phenolic compounds from lignocelluloses.

Evaluation of Bacillus aryabhattai B8W22 peroxidase for phenol removal in waste water effluents

Environmental contamination by phenol has been reported in both aquatic and atmospheric environments. This study aimed to separate and purify the peroxidase enzyme from bacteria that degrade phenol from wastewater sources. An enrichment culture of MSM was used to screen 25 bacterial isolates from different water samples for peroxidase production, six of the isolates exhibited high levels of peroxidase enzyme activity. Qualitative analysis of peroxidase revealed that isolate No. 4 had the highest halo zones (Poly-R478: 14.79 ± 0.78 mm, Azure B: 8.81 ± 0.61 mm). The promising isolate was identified as Bacillus aryabhattai B8W22 by 16S rRNA gene sequencing with accession number OP458197. As carbon and nitrogen sources, mannitol and sodium nitrate were utilized to achieve maximum peroxidase production. A 30-h incubation period was used with pH 6.0, 30 °C, mannitol, and sodium nitrate, respectively, for maximal production of peroxidase. Purified peroxidase enzyme showed 0.012 U/mg specific activity, and SDS-PAGE analysis indicated a molecular weight of 66 kDa. The purified enzyme exhibits maximum activity and thermal stability at pH values of 4.0 and 8.0, respectively, with maximum activity at 30 °C and complete thermal stability at 40 °C. In the purified enzyme, the Km value was 6.942 mg/ml and the Vmax value was 4.132 mol/ml/hr, respectively. The results demonstrated that Bacillus aryabhattai B8W22 has promising potential for degrading phenols from various phenol-polluted wastewater sources.

Response to Cold Adaption in Acinetobacter johnsonii XY27 from Spoiled Bigeye Tuna (Thunnus obesus): Membrane Protein Composition and Protein Biomarker Identification by Proteomics

Acinetobacter johnsonii is one of the major food-spoilage bacteria and can survive under cold stress. In this study, the membrane composition, membrane permeability, and energy transduction of A. johnsonii XY27 cultured at 4 and 30 °C were examined comparatively by flow cytometry combined with liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry. The Na⁺/K⁺ATPase activity, alkaline phosphatase and ATPase activity, fluorescence intensity, and cell viability in A. johnsonii XY27 increased with the decrease in cultivation temperature. The polyunsaturated fatty acid and monounsaturated fatty acids have a higher content in A. johnsonii XY27 cultured at 4 °C compared to that cultured at 30 °C, in which the contents of methyl palmitoleate, methyl myristoleate, and methyl oleate increased dramatically with decreasing temperature. Comparative proteomics analysis revealed that 31 proteins were downregulated and 4 proteins were upregulated, in which catalase-peroxidase 1 and cold shock proteins as biomarker proteins could effectively control A. johnsonii during cold adaptation.

Breakthroughs in the discovery and use of different peroxidase isoforms of microbial origin

Peroxidases are classified as oxidoreductases and are the second largest class of enzymes applied in biotechnological processes. These enzymes are used to catalyze various oxidative reactions using hydrogen peroxide and other substrates as electron donors. They are isolated from various sources such as plants, animals and microbes. Peroxidase enzymes have versatile applications in bioenergy, bioremediation, dye decolorization, humic acid degradation, paper and pulp, and textile industries. Besides, peroxidases from different sources have unique abilities to degrade a broad range of environmental pollutants such as petroleum hydrocarbons, dioxins, industrial dye effluents, herbicides and pesticides. Ironically, unlike most biological catalysts, the function of peroxidases varies according to their source. For instance, manganese peroxidase (MnP) of fungal origin is widely used for depolymerization and demethylation of lignin and bleaching of pulp. While, horseradish peroxidase of plant origin is used for removal of phenols and aromatic amines from waste waters. Microbial enzymes are believed to be more stable than enzymes of plant or animal origin. Thus, making microbially-derived peroxidases a well-sought-after biocatalysts for versatile industrial and environmental applications. Therefore, the current review article highlights on the recent breakthroughs in the discovery and use of peroxidase isoforms of microbial origin at a possible depth.