The lack of a commercially available robust and inexpensive laccase is a major barrier to the widespread application of this enzyme in various industrial sectors. By using an efficient system developed in Streptomyces lividans, we have produced by homologous expression 350 mg L(-1) of a bacterial laccase with a high purity and without any extensive purification. This is the highest production yield reported in the literature for a bacterial laccase. The secreted enzyme achieved oxidation under a wide pH range depending on the substrate: 4.0 for 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) and 9.0 for 2,6-dimethoxyphenol. Furthermore, this bacterial laccase was found to be quite resistant under various conditions. It withstands pH from 3.0 to 9.0, shows a great thermostability at 70 degrees C and was highly resistant toward conventional inhibitors. For instance, while the laccase of Trametes versicolor was completely inhibited by 1 mM NaN(3), the laccase of Streptomyces coelicolor was fully active under the same conditions. To assess application potential of this laccase, we have investigated its ability to decolourise Indigo carmine. This enzyme was able to rapidly decolourise the dye in the presence of syringaldehyde as a redox mediator.
Colored wastewater from textile industries is a consequence of dye manufacturing processes. Two percent of dyes that are produced are discharged directly in aqueous effluent and more than 10% are subsequently lost during the textile coloration process. It is not surprising that these compounds have become a major environmental concern. In that context, we have evaluated the potential use of Streptomyces coelicolor laccase for decolourization of various dyes with and without a mediator. Results showed that in all cases the combination of laccase and the mediator acetosyringone was able to rapidly decolourize, to various degrees, all the dyes tested. In 10 min, decolourization was achieved at 94% for acid blue 74, 91% for direct sky blue 6b and 65% for reactive black 5. Furthermore, decolourization was achieved at 21% for reactive blue 19 and at 39% for the direct dye Congo red in 60 min. These results demonstrate the potential use of this laccase in combination with acetosyringone, a natural mediator, for dye decolourization.
BACKGROUND: In the pulp and paper manufacturing process, pitch colloidal particles have a tendency to agglomerate and deposit on pulp fibres and equipments. They reduce the efficiency of the washer, increase the dirt count and bleach chemical consumption, reduce pulp brightness thus leading to paper defects. Triglycerides are considered to be the most problematic compounds during the manufacturing of mechanical and acidic sulfite pulps from various softwood species.
Endopolygalacturonases are among the best selling enzymes for a number of commercial applications such as
food processing. For such enzymes, a potentially important component of production cost is glycosylation. This important
modification of endopolygalacturonase has been detected for a number of species, but its real importance has not been
thoroughly studied. Here we investigated endopolygalacturonase PGU1 from Saccharomyces cerevisiae CECT 1389 produced
in S. cerevisiae INVSc 1. Combinatorial mutagenesis of recombinant S. cerevesiae PGU1 putative glycosylation
sites was performed, where asparagines 318 and 330 were replaced with either aspartic acid or glutamine. Electrophoretic
analysis of the different recombinant enzymes studied here demonstrates that the putative sites 318 and 330 are indeed
glycosylated when produced in S. cerevesiae INVSc 1. The optimal activity of these enzymes was detected at pH 4.5 and
55-60 ºC. As for stability, all enzymes studied were less than 50% active after an incubation of two hours at 50 ºC and at
pH between 4.5 and 6.0. Glycosylation did not provide any significant stabilisation of PGU1, but the replacement of Asn
330 with Gln had a deleterious effect on stability. The secondary structure spectra are characteristics of proteins mostly
composed of beta sheets. The Tm values measured for PGU1, PGU1 deglycosylated with endo H, and three mutants
ranged from 53 to 55.4ºC, indicating that glycosylation had no impact on PGU1 conformation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.