Increasing the scale of peroxidase production by Streptomyces sp. strain BSII#1

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.

Bioprospecting of novel peroxidase from Streptomyces coelicolor strain SPR7 for carcinogenic azo dyes decolorization

Peroxidase (POX) is a heme-containing oxidoreductase, its voluminous immuno-diagnostic and bioremediatory intuitions have incited optimization and large scale-generation from novel microbial repertoires. Azo dyes are the most detrimental classes of synthetic dyes and they are the common ecotoxic industrial pollutants in wastewater. In addition, azo dyes are refractory to degradation owing to their chemical nature, comprising of azoic linkages, amino moieties with recalcitrant traits. Moreover, they are major carcinogenic and mutagenic on humans and animals, whereby emphasizing the need for decolorization. In the present study, a novel POX from Streptomyces coelicolor strain SPR7 was investigated for the deterioration of ecotoxic dyestuffs. The initial medium component screening for POX production was achieved using, One Factor at a Time and Placket-Burman methodologies with starch, casein and temperature as essential parameters. In auxiliary, Response Surface Methodology (RSM) was recruited and followed by model validation using Back propagation algorithm (BPA). RSM-BPA composite approach prophesied that combination of starch, casein, and temperature at optimal values 2.5%, 0.035% and 35 °C respectively, has resulted in 7 folds enhancement of POX outturn (2.52 U/mL) compared to the unoptimized media (0.36 U/mL). The concentrated enzyme decolorized 75.4% and 90% of the two azo dyes with lignin (10 mM), respectively. Hence, this investigation confirms the potentiality of mangrove actinomycete derived POX for elimination of noxious azo dyes to overcome their carcinogenic, mutagenic and teratogenic effects on humans and aquatic organisms.

Agroresidues enhanced peroxidase activity expression by Bacillus sp. MABINYA-1 under submerged fermentation

Agroresidues have continued to gain preference over conventional carbon sources for microbial enzyme production due to the low price and abundance in the environment. Therefore, this study aimed at improving peroxidase yield by Bacillus sp. MABINYA-1 (BMAB-1) using agroresidues under submerged fermentation. The culture parameters that support maximum peroxidase yield by BMAB-1 was initially determined and the results showed that peroxidase activity expression was optimum at pH 5, 30 °C and 150 rpm while veratryl alcohol and ammonium sulphate served as the best peroxidase-inducer and inorganic nitrogen source, respectively. BMAB-1 exhibited maximum peroxidase expression (17.50 ± 0.10 U/mg) at 72 h using kraft lignin liquid medium (KLLM) under the optimized culture conditions. Upon utilization of selected agroresidues (sawdust, wheat straw and maize stover) as sole carbon sources by BMAB-1 in the fermentation process, peroxidase activity was significantly enhanced when compared with glucose (14.91 ± 0.31 U/mg) and kraft lignin (17.50 ± 0.10 U/mg). Sawdust produced the highest peroxidase yield (47.14 ± 0.41 U/mg), followed by maize stover (37.09 ± 0.00 U/mg) while wheat straw yielded the lowest peroxidase specific activity (21.65 ± 0.35 U/mg). This indicates that utilization of sawdust by BMAB-1 resulted in 3.2- and 2.7-fold increase in peroxidase activity expression as compared to glucose and kraft lignin, respectively. The aptitude of BMAB-1 to utilize agroresidues would reduce the cost of peroxidase production by the bacteria since the substrates are cheaper than the conventional carbon sources and are, as well, more readily available.

Production and characterisation of a novel actinobacterial DyP-type peroxidase and its application in coupling of phenolic monomers

The extracellular peroxidase from Streptomyces albidoflavus BSII#1 was purified to near homogeneity using sequential steps of acid and acetone precipitation, followed by ultrafiltration. The purified peroxidase was characterised and tested for the ability to catalyse coupling reactions between selected phenolic monomer pairs. A 46-fold purification of the peroxidase was achieved, and it was shown to be a 46 kDa haem peroxidase. Unlike other actinobacteria-derived peroxidases, it was only inhibited (27 % inhibition) by relatively high concentrations of sodium azide (5 mM) and was capable of oxidising eleven (2,4-dichlorophenol, 2,6-dimethoxyphenol, 4-tert-butylcatechol, ABTS, caffeic acid, catechol, guaiacol, l-DOPA, o-aminophenol, phenol, pyrogallol) of the seventeen substrates tested. The peroxidase remained stable at temperatures of up to 80 °C for 60 min and retained >50 % activity after 24 h between pH 5.0-9.0, but was most sensitive to incubation with hydrogen peroxide (H₂O₂; 0.01 mM), l-cysteine (0.02 mM) and ascorbate (0.05 mM) for one hour. It was significantly inhibited by all organic solvents tested (p ≤ 0.05). The K_m and V_max values of the partially purified peroxidase with the substrate 2,4-DCP were 0.95 mM and 0.12 mmol min^-1, respectively. The dyes reactive blue 4, reactive black 5, and Azure B, were all decolourised to a certain extent: approximately 30 % decolourisation was observed after 24 h (1 μM dye). The peroxidase successfully catalysed coupling reactions between several phenolic monomer pairs including catechin-caffeic acid, catechin-catechol, catechin-guaiacol and guaiacol-syringaldazine under the non-optimised conditions used in this study. Genome sequencing confirmed the identity of strain BSII#1 as a S. albidoflavus strain. In addition, the genome sequence revealed the presence of one peroxidase gene that includes the twin arginine translocation signal sequence of extracellular proteins. Functional studies confirmed that the peroxidase produced by S. albidoflavus BSII#1 is part of the dye-decolourising peroxidase (DyP-type) family.

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

This study sought to determine the process conditions for optimum peroxidase production by a Bacillus species (Bacillus sp. FALADE-1-KX640922) isolated from Hogsback forest reserve in South Africa and characterize the peroxidase gene in the bacteria. We optimized peroxidase production by manipulating the environmental and nutritional parameters under submerged fermentation. Subsequently, the gene encoding heme-peroxidase was determined through nested polymerase chain reaction and Sanger DNA sequencing. The studied bacteria had maximum peroxidase production at pH 8, 30 °C and 150 rpm. The addition of guaiacol to lignin fermentation medium enhanced peroxidase production by over 100 % in the studied bacteria. However, the other lignin monomers (veratryl alcohol, vanillin, vanillic acid and ferulic acid) repressed the enzyme activity. Modification of the fermentation medium with ammonium sulphate gave the maximum peroxidase yield (8.87 U mL⁻¹). Under the predetermined culture conditions, Bacillus sp. FALADE-1 expressed maximum specific peroxidase activity at 48 h (8.32 U mg⁻¹). Interestingly, a search of the sequenced gene in PeroxiBase showed 100% similarity to Sporotrichum thermophile catalase-peroxidase gene (katG), as well, the deduced protein sequence clustered with bacterial catalase-peroxidases and had a molecular weight of about 11.45 kDa with 7.01 as the estimated isoelectric point. Subsequently, the nucleotide sequence was deposited in the National Center for Biotechnology Information (NCBI) repository with the accession number MF407314. In conclusion, Bacillus sp. FALADE-1 is a promising candidate for improved peroxidase production.

Exoproduction and Molecular Characterization of Peroxidase from Ensifer adhaerens

The increased industrial application potentials of peroxidase have led to high market demand, which has outweighed the commercially available peroxidases. Hence, the need for alternative and efficient peroxidase-producers is imperative. This study reported the process parameters for enhanced exoperoxidase production by Ensifer adhaerens NWODO-2 (accession number: KX640918) for the first time, and characterized the enzyme using molecular methods. Peroxidase production by the bacteria was optimal at 48 h, with specific productivity of 12.76 U mg−1 at pH 7, 30 °C and 100 rpm in an alkali lignin fermentation medium supplemented with guaiacol as the most effective inducer and ammonium sulphate as the best inorganic nitrogen source. Upon assessment of some agricultural residues as sources of carbon for the enzyme production, sawdust gave the highest peroxidase productivity (37.50 U mg−1) under solid-state fermentation. A search of the polymerase chain reaction (PCR)-amplified peroxidase gene in UniProtKB using blastx showed 70.5% similarity to an uncharacterized protein in Ensifer adhaerens but phylogenetic analysis suggests that the gene may encode a catalase-peroxidase with an estimated molecular weight of approximately 31 kDa and isoelectric point of about 11. The nucleotide sequence of the detected gene was deposited in the GenBank under the accession number MF374336. In conclusion, the ability of the strain to utilize lignocellulosic materials for peroxidase production augurs well for biotechnological application as this would greatly reduce cost, which is a major challenge in industrial enzyme production.

Agrowastes utilization by Raoultella ornithinolytica for optimal extracellular peroxidase activity

The industrial applications and prospects of microbial peroxidase are on the upwards trend, thus necessitating the search for sources with high turnaround time. Actinobacterial species have been a major source of peroxidase for the obvious reasons of having robust metabolite expression capabilities. However, other bacteria species have been underexplored for peroxidase production, hence the motivation for the investigation into the peroxidase production potential of Raoultella ornithinolytica OKOH-1 (KX640917). The bacteria expressed optimum specific peroxidase activity of 16.48 ± 0.89 U mg^-1 , which is higher than those previously reported. The optimal fermentation conditions were pH 5 (3.44 ± 0.64 U mL^-1 ), incubation temperature of 35 °C (5.25 ± 0.00 U mL^-1 ), and agitation speed of 150 rpm (9.45 ± 2.57 U mL^-1 ), with guaiacol and ammonium chloride as the best inducer and nitrogen supplement, respectively. On valorization of agrowastes as a sole carbon source for the secretion of peroxidase, sawdust gave the best peroxidase yield (15.21 ± 2.48 U mg^-1 ) under solid-state fermentation. Also, a nonperoxide-dependent enzyme activity, which suggests probable laccase activity, was observed. The ability of the bacteria to utilize agrowastes is highly economical and as well a suitable waste management strategy. Consequently, R. ornithinolytica OKOH-1 is a promising industrial strain with dexterity for enhanced peroxidase production.

Streptomyces spp. in the biocatalysis toolbox

About 20,100 research publications dated 2000-2017 were recovered searching the PubMed and Web of Science databases for Streptomyces, which are the richest known source of bioactive molecules. However, these bacteria with versatile metabolism are powerful suppliers of biocatalytic tools (enzymes) for advanced biotechnological applications such as green chemical transformations and biopharmaceutical and biofuel production. The recent technological advances, especially in DNA sequencing coupled with computational tools for protein functional and structural prediction, and the improved access to microbial diversity enabled the easier access to enzymes and the ability to engineer them to suit a wider range of biotechnological processes. The major driver behind a dramatic increase in the utilization of biocatalysis is sustainable development and the shift toward bioeconomy that will, in accordance to the UN policy agenda "Bioeconomy to 2030," become a global effort in the near future. Streptomyces spp. already play a significant role among industrial microorganisms. The intention of this minireview is to highlight the presence of Streptomyces in the toolbox of biocatalysis and to give an overview of the most important advances in novel biocatalyst discovery and applications. Judging by the steady increase in a number of recent references (228 for the 2000-2017 period), it is clear that biocatalysts from Streptomyces spp. hold promises in terms of valuable properties and applicative industrial potential.