Abstract
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.
Highlights
Peroxidase has continued to gain attention, probably, due to the robust industrial application potentials; notably, the emerging role in bioremediation that has extensively been documented (Min et al 2015; Taboada-Puig et al 2015; Falade et al 2018)
Bioinformatics analysis involving the use of Basic Local Alignment Search Tool (BLAST) in the National Center for Biotechnology Information (NCBI) database revealed the identity of the bacteria as a Bacillus species as it had 99% similarity to Bacillus sp
Evaluation of culture conditions for maximum peroxidase activity expression The various culture parameters that promote maximum peroxidase expression by Bacillus sp. MABINYA-1 (BMAB-1) was initially determined because such microbial growth factors have been linked to persistent enzyme secretion
Summary
Peroxidase has continued to gain attention, probably, due to the robust industrial application potentials; notably, the emerging role in bioremediation that has extensively been documented (Min et al 2015; Taboada-Puig et al 2015; Falade et al 2018). Peroxidases are characterized by promising application potential in the bioenergy sector as members of class-II peroxidase–catalase superfamily (lignin peroxidase, manganese peroxidase and versatile peroxidase) are efficient lignin degraders. They are part of the suggested “lignocellulolytic enzyme. Simple sugars may not be the most appropriate carbon source for production of inducible enzymes including peroxidases, which may require the introduction of an “inducer” in the growth medium. It is, necessary to explore cheap alternative carbon sources capable of inducing increased enzyme expression
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