A new laccase (EC 1.10.3.2) produced by Streptomyces cyaneus CECT 3335 in liquid media containing soya flour (20 g per liter) was purified to homogeneity. The physicochemical, catalytic, and spectral characteristics of this enzyme, as well as its suitability for biobleaching of eucalyptus kraft pulps, were assessed. The purified laccase had a molecular mass of 75 kDa and an isoelectric point of 5.6, and its optimal pH and temperature were 4.5 and 70°C, respectively. The activity was strongly enhanced in the presence of Cu 2؉ , Mn 2؉ , and Mg 2؉and was completely inhibited by EDTA and sodium azide. The purified laccase exhibited high levels of activity against 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) and 2,6-dimethoxyphenol and no activity against tyrosine. The UV-visible spectrum of the purified laccase was the typical spectrum of the blue laccases, with an absorption peak at 600 nm and a shoulder around 330 to 340 nm. The ability of the purified laccase to oxidize a nonphenolic compound, such as veratryl alcohol, in the presence of ABTS opens up new possibilities for the use of bacterial laccases in the pulp and paper industry. We demonstrated that application of the laccase from S. cyaneus in the presence of ABTS to biobleaching of eucalyptus kraft pulps resulted in a significant decrease in the kappa number (2.3 U) and an important increase in the brightness (2.2%, as determined by the International Standard Organization test) of pulps, showing the suitability of laccases produced by streptomycetes for industrial purposes.Because of their potential for biotechnological applications in areas such as biobleaching, increasing the strength of cellulose fibers, textile dye or stain bleaching, and bioremediation, attention is currently being paid to laccases (2,23,30,43,50). These enzymes are widely distributed in plants and fungi, but until now laccase activity has been reported in only a few bacteria, including Azospirillum lipoferum, Marinomonas mediterranea, Streptomyces griseus, and Bacillus subtilis (1,15,20,22,41,45). A number of roles for laccases in bacterial systems have been suggested and include roles in melanin production and spore coat resistance and involvement in morphogenesis (15,22). In Streptomyces cyaneus, a laccase-type phenol oxidase was found to be produced during growth under solid-substrate fermentation conditions, and it was suggested that this enzyme was involved in the solubilization and mineralization of lignin from wheat straw (5). Further studies demonstrated that this organism could be used to improve the qualities of pulp after 2 weeks of incubation under solid-substrate fermentation conditions (6). However, to date there have been no reports describing the involvement of bacterial laccases in the oxidation of nonphenolic compounds in the presence of mediators. The specific activities of these enzymes with lignin and related substrates have not been examined yet.Laccases are considered some of the most promising enzymes for future industrial applications in the pulp ...

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Wildfires subject soil microbes to extreme temperatures and modify their physical and chemical habitat. This might immediately alter their community structure and ecosystem functions. We burned a fire-prone shrubland under controlled conditions to investigate (1) the fire-induced changes in the community structure of soil archaea, bacteria and fungi by analysing 16S or 18S rRNA gene amplicons separated through denaturing gradient gel electrophoresis; (2) the physical and chemical variables determining the immediate shifts in the microbial community structure; and (3) the microbial drivers of the change in ecosystem functions related to biogeochemical cycling. Prokaryotes and eukaryotes were structured by the local environment in pre-fire soils. Fire caused a significant shift in the microbial community structure, biomass C, respiration and soil hydrolases. One-day changes in bacterial and fungal community structure correlated to the rise in total organic C and NO(3)(-)-N caused by the combustion of plant residues. In the following week, bacterial communities shifted further forced by desiccation and increasing concentrations of macronutrients. Shifts in archaeal community structure were unrelated to any of the 18 environmental variables measured. Fire-induced changes in the community structure of bacteria, rather than archaea or fungi, were correlated to the enhanced microbial biomass, CO(2) production and hydrolysis of C and P organics. This is the first report on the combined effects of fire on the three biological domains in soils. We concluded that immediately after fire the biogeochemical cycling in Mediterranean shrublands becomes less conservative through the increased microbial biomass, activity and changes in the bacterial community structure.

Currently, there is increasing interest in assessing the potential of bacterial laccases for industrial and environmental applications especially in harsh conditions. The environmental impact of the textile industry requires novel and effective technologies to mitigate the presence of dyes in wastewaters before discharging into the environment. Dyes usually remain stable in the presence of a variety of chemicals, light and are recalcitrant to microbial degradation. Among available technologies the biological treatments offer environmentally friendly strategies for decolorizing and detoxifying these compounds. The recent discovery of versatile laccases in streptomycetes opens up new opportunities for their commercial application. The aim of this study is to assess the potential of a novel bacterial laccase SilA produced by Streptomyces ipomoeae CECT 3341 active over wide temperature and pH ranges for use as an eco-friendly, biological treatment for the degradation of textile dyes. Insights into the enhancement of the oxidative action of this enzyme through the use of natural redox mediators are presented together with an assessment of the potential toxicity of the degradation products. Our results confirm that the combination of the laccase and natural mediators such as acetosyringone and methyl syringate enhanced the decolorization and detoxification of a variety of textile dyes up to sixfold and 20-fold, respectively. Mediator concentration was found to have a significant effect (p < 0.05) on dye decolorization at 60 °C; thus, the decolorization of Acid Orange 63 increased from 6 to 70-fold when the mediator concentration was increased from 0.1 to 0.5 mM. Further, the toxicity of tartrazine decreased 36-fold when the SilA-MeS system was used to decolorize the dye. The thermal properties of the SilA coupled with the stability of SilA at high pH suggest a potential commercial application for use in the decolorization of textile wastewaters which generally are performed at high temperature (>55 °C) and salinity and neutral pH, conditions which are unfavourable for conventional fungal laccases.

This work describes the solid-state fermentation (SSF) of wheat straw with Streptomyces sp. MDG147 and further soda-pulping process to obtain wheat straw soda lignins (WSLs). Subsequently, these WSLs were NCO-functionalized with 1,6-hexamethylene diisocyanate and then dispersed in castor oil to achieve stable oleogels. The WSLs were characterized using standard analytical methods, gel permeation chromatography, Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. Rheological properties of oleogels were determined by means of small-amplitude oscillatory shear and viscous flow measurements. The enzymatic profile and production of lignin−carbohydrate complexes were recorded along the growth time of Streptomyces, whose life cycle was achieved after 7 days. NCO-functionalized WSL was able to chemically interact with castor oil via urethane bonding, providing oleogels with suitable rheological characteristics. Linear viscoelastic functions and viscosity values of oleogels were higher when wheat straw was submitted to SSF using Streptomyces, turning out in stronger oleogels.