Strategies for Enhancing Laccase Yield from Streptomyces psammoticus and Its Role in Mediator-based Decolorization of Azo Dyes

Abstract

Enhanced production of laccases from Streptomyces psammoticus in solid-state fermentation was carried out using two different strategies: laccase inducers and scale-up process. Laccase yield was enhanced by a wide range of aromatic inducers. The best inducer was pyrogallol, which yielded 116 U/g as compared to the control (55.4 U/g). Scale-up studies in packed bed bioreactor was performed at different aeration rates. Aeration at 1.5 vvm was identified as the optimum condition for laccase production (75.4 U/g) in the column bioreactor. The enzyme yield was enhanced further by combining the best conditions from the first two experiments. Fermentation was carried out in bioreactors in the presence of 1 mM pyrogallol, which resulted in 3.9-fold increase in laccase yield (215.6 U/g). The role of laccase in azo dye decolorization was evaluated in the presence of four different laccase mediators, at different concentrations. 1-Hydroxybenzotriazole (HOBT) proved to be the best mediator for S. psammoticus laccase and decolorized the azo dyes efficiently. Acid orange, Methyl orange, and Bismarck brown were decolorized at the rates of 86%, 71%, and 75% respectively, by HOBT.

Controlling the simultaneous production of laccase and lignin peroxidase from Streptomyces cinnamomensis by medium formulation

“…The medium for laccase and LiP production from S. cinnamomensis by SmF (Table 1) was prepared in Erlenmeyer flasks with veratryl alcohol as inducer [5,29]. After inoculation with 10% (7.5 mL v/v) of bacterial cell suspension containing 1.5 × 10 7 CFU/mL, 75 mL medium from each run was cultured at were cultured at 25°C with shaking at 120 to 130 rpm.…”

Laccase Properties, Physiological Functions, and Evolution

“…The SLAC displays an unprecedentedly high pH optimum (9.4) for oxidation of 2,6-dimethoxyphenol (DMP); however, the recombinantly expressed enzyme exhibits paramagnetic properties typical for laccases [106]. Next to fungi, it is believed that actinomycetes are potent producers of laccases in nature [107], and their SLACs are thought to represent key evolutionary intermediates of the three-domain MCOs [16]. Still, their crystal structure resembles the structure of nitrite reductase or human ceruloplasmin more than that of a typical laccase [108,109].…”

“…The prokaryotic laccases described so far vary greatly in size from 32 to 180 kDa and occur as monomers, trimers, and tetramers. Although there is undeniable evidence for prokaryotic protein glycosylation [110], glycosylation of bacterial MCOs has not been investigated extensively and there are only few reports related to the carbohydrate content of bacterial laccases [97,107,111]. Similarly, very little is known about the electrochemistry of prokaryotic MCOs (Table S1).…”

Optimization of phenoxazinone synthase production by response surface methodology and its application in Congo red decolourization

“…Laccases produced from Streptomyces have been employed in previous studies to decolorize the recalcitrant dyes (Dubé et al 2008;Niladevi et al 2008) including Congo red, a dye widely used in textile dyeing and resistant to biodegradation treatment. To explore the potential application of PHS in dye degradation, we studied decolourization of Congo red by crude PHS extract and examined the effects of various factors on Congo red degradation.…”