Agrowastes utilization by Raoultella ornithinolytica for optimal extracellular peroxidase activity

Abstract

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.

Exoproduction and Molecular Characterization of Peroxidase from Ensifer adhaerens

“…However, Musengi et al [12] observed optimum peroxidase production by Streptomyces sp. BSII#1 at pH 8 while we recorded pH 5 as the optimal pH for peroxidase production by Raoultella ornithinolytica OKOH-1 in a recent study [25]. It is worthy of note that the characteristic production of peroxidase by the test bacteria at a neutral pH augurs well for biotechnological applications as the large volume of acid and base required for pH adjustment would be saved [37], consequently, reducing the cost of peroxidase production.…”

“…It is worthy of note that the characteristic production of peroxidase by the test bacteria at a neutral pH augurs well for biotechnological applications as the large volume of acid and base required for pH adjustment would be saved [37], consequently, reducing the cost of peroxidase production. recent study [25]. It is worthy of note that the characteristic production of peroxidase by the test bacteria at a neutral pH augurs well for biotechnological applications as the large volume of acid and base required for pH adjustment would be saved [37], consequently, reducing the cost of peroxidase production.…”

“…The reason for the inconsistencies in the optimal temperature for peroxidase production by the different bacteria species is unclear. However, all the temperatures that supported maximum peroxidase production by the various organisms are in the mesophilic range [25]. The decline in the enzyme production by Ensifer adhaerens NWODO-2 observed at temperatures lower and higher than 30 o C (Figure 1b) may probably be due to decrease in metabolic activities, which consequently, may inhibit the organism growth and enzyme biosynthesis [40].…”

“…The supernatant recovered from the culture was assayed for exoperoxidase and non-peroxide dependent exoenzyme production every 24 h [23]. Also, the total concentration of protein was estimated according to the method of Bradford [24] as reported earlier in our recent study [25]. Then, the bacterial growth was determined by the optical density at 600 nm.…”

“…Some agricultural residues (sawdust, wheat straw and corn stover) obtained from Alice metropolis, South Africa, were utilized for exoperoxidase production using solid state fermentation (SSF). The residues were prepared as described by Falade et al [25] and, subsequently, were utilized as substrates for exoperoxidase production using the method described by Neifar and coauthors [26] with slight modifications reported in our previous study [25].…”