Random mutants of a Pleurotus ostreatus laccase as new biocatalysts for industrial effluents bioremediation

Aims: To select better performing laccase variants among the 2300 randomly mutated variants of Pleurotus ostreatus POXA1b laccase to develop improved laccase‐based biocatalysts. Methods and Results: Screening of collections of 2300 randomly mutated variants of POXA1b was performed by assaying activity towards the phenolic substrate 2,6‐dimethoxyphenol. Two new variants endowed with higher enzyme activity than the wild‐type laccase were characterized, and their ability to decolourize industrial dyes with complex trisazo‐, polyazo‐ and stilbene‐type structures, in the absence of mediators, was demonstrated. One of the mutants (2L4A) was also proved to be highly stable at both acidic and alkaline pH values (displaying a half‐life of around 1 month at the pH levels of both 5 and 10). Conclusions: In comparison with the wild‐type laccase, the new selected 2L4A mutant shows a significant increase in stability at acidic pH, whilst storing its high stability at alkaline pH. This variant also represents a more versatile enzyme with respect to both the variety of xenobiotics degraded and the operative conditions. Significance and Impact of the Study: This work represents the first example of improvement of a basidiomycete laccase for industrial effluents bioremediation by directed evolution.     

Biological Treatment of a Pulp and Paper Industry Effluent by Pleurotus spp.

In this work, the ability of Pleurotus spp.:P. sajor-caju; P. platypus and P. citrinopileatus to treat pulp and paper mill effluent on a laboratory and pilot scale were studied. On the laboratory scale treatment, P. sajor-caju decolorized the effluent by 66.7% on day 6 of incubation. Inorganic chloride liberated by P. sajor-caju was 230.9% (814.0 mg/dl) and the COD was reduced by 61.3% (1302.0 mg/dl) on day 10 of treatment. In the pilot scale treatment maximum decolorization was obtained by P. sajor-caju (60.1%) on day 6 of the incubation. Inorganic chloride content was increased by 524.0 mg/dl (113.0%) and the COD was reduced by 1442.0 mg/dl (57.2%) by P. sajor-caju on day 7 of incubation. These results revealed that the treatment of pulp and paper mill effluent by P. sajor-caju proved as better candidate for the purpose than P. platypus and P. citrinopileatus.     

Factors affecting mushroom Pleurotus spp.

Pleurotus genus is one of most extensively studied white-rot fungi due to its exceptional ligninolytic properties. It is an edible mushroom and it also has several biological effects, as it contains important bioactive molecules. In basidiomycete fungi, lignocellulolytic enzymes are affected by many typical fermentation factors, such as medium composition, ratio of carbon to nitrogen, pH, temperature, air composition, etc. The survival and multiplication of mushrooms is related to a number of factors, which may act separately or have interactive effects among them. Out that understanding challenges in handling Pleurotus species mushroom requires a fundamental understanding of their physical, chemical, biological and enzymatic properties. This review presents a practical checklist of available intrinsic and extrinsic factors, providing useful synthetic information that may help different users. An in-depth understanding of the technical features is needed for an appropriate and efficient production of Pleurotus spp.     

低温处理对侧耳属栽培菌株菌丝体酯酶同工酶谱的影响

应用垂直板聚丙烯酰胺凝胶电泳对不同低温、不同缓化方式处理后的侧耳属(Pleurotus)不同栽培种12个菌株进行酯酶(EST)同工酶谱分析。结果表明:不同菌株对低温的耐受能力不同,缓化方式对于酯酶基因表达的影响不同,但低温并没有使其酯酶酶活力完全丧失。     

Phenol degradation and colour removal in submerged culture of Pleurotus sajor-caju with paper mill effluents

The fungus Pleurotus sajor-caju secretes phenol-oxidases that enable the use of recalcitrant compounds as substrates. The residues of paper manufacture contain high lignin levels, which gives the effluents a characteristic brownish colour. To test the potential of P. sajor-caju cultures on reducing these parameters, we used 90% of raw effluents from medium consistency oxygen delignification and bleaching stages plus 10% of mineral solution and different levels of glucose (5–15 g L^?1) as substrate. We observed a greater fungal biomass in cultures using effluent than in controls. Cultures containing 10 to 15 g L^?1 of glucose resulted in about 42% colour reduction. The polyphenol content was also reduced by 58.9% by the 13th day of culture. In addition, we observed the secretion of laccases (211.44 U mL^?1 and 45.98 U mL^?1 using ABTS and syringaldazine, respectively) and peroxidases (6.11 U mL^?1-ABTS) both peaking at the 7th day of culture and with similar kinetics of production in different glucose concentrations.     

Phenol degradation and colour removal in submerged culture of Pleurotus sajor-caju with paper mill effluents

The fungus Pleurotus sajor-caju secretes phenol-oxidases that enable the use of recalcitrant compounds as substrates. The residues of paper manufacture contain high lignin levels, which gives the effluents a characteristic brownish colour. To test the potential of P. sajor-caju cultures on reducing these parameters, we used 90% of raw effluents from medium consistency oxygen delignification and bleaching stages plus 10% of mineral solution and different levels of glucose (5-15 g L^-1) as substrate. We observed a greater fungal biomass in cultures using effluent than in controls. Cultures containing 10 to 15 g L^-1 of glucose resulted in about 42% colour reduction. The polyphenol content was also reduced by 58.9% by the 13th day of culture. In addition, we observed the secretion of laccases (211.44 U mL^-1 and 45.98 U mL^-1 using ABTS and syringaldazine, respectively) and peroxidases (6.11 U mL^-1-ABTS) both peaking at the 7th day of culture and with similar kinetics of production in different glucose concentrations.     

Phenol degradation by yeasts isolated from industrial effluents

Yeast strains of the genera Aureobasidium, Rhodotorula and Trichosporon were isolated from stainless steel effluents and tested for their ability to utilize phenol as the sole carbon source. Fourteen strains grew in the presence of up to 10 mm phenol. Only the strain Trichosporon sp. LE3 was able to grow in the presence of up to 20 mm phenol. An inhibitory effect was observed at concentrations higher than 11 mm, resulting in reduction of specific growth rates. Phenol degradation was a function of strain, time of incubation and initial phenol concentration. All strains exhibited activity of catechol 1,2-dioxygenase and phenol hydroxylase in free cell extracts from cells grown on phenol, suggesting that catechol was oxidized by the ortho type of ring fission. Addition of glucose and benzoate reduced the phenol consumption rate, and both substrates were used simultaneously. Glucose concentrations higher than 0.25% inhibited the induction of phenol oxidation by non-proliferating cells and inhibited phenol oxidation by pre-induced cells.     

Biomethanation of industrial effluents for energy recovery in China

Summary China has large amounts of effluents containing high organic loads. It is paying special attention to intensifying the process of biomethanation to increase the biogas production per unit of reactor volume and to reduce pollution. At present, a few plants have been realized such as two plants treating urban wastewater sludge, one plant working on effluents from the citric acid industry and three plants working with effluent from three alcohol distilleries. Biomethanation of waste liquor from pulp processing by lime has been studied on the laboratory scale and 79% COD removal has been obtained. An Upflow Anaerobic Sludge Blanket (UASB) pilot plant of 24 m³ fed with filtered residual liquor from a distillery produces 5 m³/m³ digester per day with a COD removal of 93%. Until now the extension of biomethanation of industrial effluents has been limited because the COD content of the effluents is still beyond the effluent discharge standards.

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Resumen China tiene una gran cantidad de efluentes con un nivel de polución orgánica elevado. Actualmente se está prestando una atención especial a los procesos de biometanación para poder incrementar la producción de biogas por unidad de volumen del reactor y aumentar la reducción del nivel de polución. Hasta ahora tan solo existen 2 plantas de tratemiento de aguas residuales urbanas, 1 planta que trabajan con efluentes de una fábrica de ácido ctrico y 3 plantas que trabajan con efluentes de 3 destilerias de alcool. Se ha estudiado a nivel de laboratorio la biometanación del licor de desecho del tratamiento de la pulpa con cal obteniéndose una disminución del 79% del COD. Una planta piloto UASB de 24 m³ alimentada con licor residual de destilerias filtrado produce 5 m³ y por día con una disminución del COD del 93%. Hasta el momento la expansión de la biometanación se ha visto frenada porque el contenido en COD de los efluentes no está aún contemplado en la normativa sobre vertidos líquidos.

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Résumé La Chine produit de grandes quantités d'effluents à fortes concentrations en matières organiques. Elle attache donc une importance particulière à l'intensification des procédés de biométhanisation afin d'en augmenter la productivité et l'effet dépolluant. A l'heure actuelle il existe quelques réalisations telles que deux installations de traitement des boues d'eaux résiduaires urbaines, un installation alimentées par les effluents d'industries de production d'acide citrique, et trois installations traitant des effluents de distillerie d'alcool. La biométhanisation d'eaux résiduaires résultant du processing de la pâte à papier par la chaux a été étudiée à l'échelle laboratoire et une réduction de 79% de la DCO a été obtenue. Une installation pilote (Upflow Anaerobic Sludge Blanket, UASB) de 24 m³ alimentée par les eaux résiduaires filtrées d'une distillerie produit 5 m³ par m³ et par jour avec une élimination de 93% de la DCO. Jusqu'à présent le développement de la biométhanisation d'effluents industriels a été limitée par un contenu en DCO des effluents méthanisés encore supérieur aux normes de décharge.

     

Decolorization of industrial effluents containing reactive dyes by actinomycetes

Abstract Actinomucete strains have been identified which decolorize effluents containing different types of reactive dyes. Adsorption of anthraquinone, phthalocyanine and azo dyes to the cells of some of the strains resulted in the decolorization of the effluents, but no degradation of the dyes was observed. In contrast, effluents containing an azo-copper complex and a formazan-copper complex dye were almost completely decolorized by several of the strains without adsorption to the cells. The observed changes in the visible spectra indicated a degradation during incubation with she strains.     

侧耳属真菌经济利用的研究进展

侧耳属真菌分布广泛、是大型真菌中生物多样性最为丰富的类群之一。其含有丰富的多糖、蛋白质、氨基酸、脂肪酸等生物活性物质,在食品、保健和医药等方面具有广泛用途。侧耳属真菌通过产生木质素氧化酶、锰过氧化物酶和漆酶等酶类降解多环芳烃、染料、工农业废弃物等有害物,并广泛应用于纺织厂、造纸厂、橄榄油厂废水及城市废水的处理。同时,侧耳属是食用菌家族中利用基质最为广泛的真菌,可以多种农业、林业、轻工业等废弃物为基质进行栽培生产,且生物学效率较高,具重要农业生产应用价值。     

侧耳属食用菌高温胁迫条件优化研究

侧耳属真菌是我国最大规模栽培的食用菌,主要是糙皮侧耳Pleurotus ostreatus和白黄侧耳P. cornucopiae。高温是影响侧耳产量和质量的重要因子之一,确定高温胁迫条件是开展高温胁迫机制研究的方法学基础。以糙皮侧耳和白黄侧耳的11个菌株为材料,以硫代巴比妥酸反应产物（thiobarbituric acid reactive substances,TBARS）含量为主要生理指标,结合菌丝形态和生长等微生物学参数,开展了双核体菌丝高温胁迫条件的研究,包括胁迫的适宜温度、时间和菌龄等。结果表明,所有供试材料,高温胁迫后菌丝体内TBARS含量在28-40℃、0-48h范围内与温度和时间呈正相关,与之后的恢复生长率呈负相关,高温胁迫后菌丝体内TBARS含量和之后的恢复生长能力均与自身菌丝体生长和子实体形成的适宜温度无关。TBARS含量可作为菌丝高温胁迫生理研究条件确定的指标。与植物的最适温度加10℃不同,基于TBARS含量的糙皮侧耳和白黄侧耳高温胁迫研究条件应为Difco^TM Potato Dextrose Agar培养基,菌丝培养3d,最适温度加12℃,高温胁迫处理48h。     

Selective biosorption and recovery of Ruthenium from industrial effluents with Rhodopseudomonas palustris strains

This study demonstrated for the first time the possibility to remove and partially recover the Ruthenium contained in industrial effluents by using purple non sulfur bacteria (PNSB) as microbial biosorbents. Up to date, the biosorption was only claimed as possible tool for the removal of the platinum-group metals (PGM) but the biosorption of Ru was never experimentally investigated. The PNSBs tested have adsorbed around 40?mg?g (dry biomass)(-1) of the Ru contained in the real industrial effluents. At the end of the bioremoval experiments, the amount of Ru recovered from the biomass ranged from 42?% to 72?% of that adsorbed by PNSB, depending by the characteristics of the Ru effluent used. In any case, the use of microbial sorbents such as PNSB for the biosorption and recovery of Ru can be considered a way to reduce both the costs and the impact on the environment of the mining activities needed to obtain the increasing amounts of this rare and precious metal requested by the industrial activities related to its use.     

Role of micronutrients in activated sludge-based biotreatment of industrial effluents

Industrial processes often produce wastewaters that resist biological treatment owing to the unfamiliarity of some components to biological systems. Availability of nutrients determines the community structure of the activated sludge and hence the efficiency of the degradation process. Micronutrients influence the bacteria involved in waste degradation and also the species diversity within the sludge. The requirements for and toxicity of different micronutrients vary according to the nature of the waste and the ecology of the sludge. Adding micronutrients to biological treatment processes is one possible approach to upgrading an existing facility in order to deal with increasing volumes and strengths of industrial wastewaters and the tightening discharge legislation.     

Biosorptive removal of cadmium from contaminated groundwater and industrial effluents

The cadmium removing capacity of a biosorbent Calotropis procera, a perennial wild plant, is reported here. The biomass was found to possess high uptake capacity of Cd(II). Adsorption was pH dependent and the maximum removal was obtained at two different pH i.e. pH 5.0 and 8.0. Maximum biosorption capacity in batch and column mode was found to be 40 and 50.5 mg/g. The adsorption equilibrium (> or =90% removal) was attained within 5 min irrespective of the cadmium ion concentration. Interfering ions viz. Zn(II), As(III), Fe(II), Ni(II) interfered only when their concentration was higher than the equimolar ratio. The Freundlich isotherm best explained the adsorption, yet the monolayer adsorption was also noted at lower concentrations of Cd(II). The FTIR analysis indicates the involvement of hydroxyl (-OH), alkanes (-CH), nitrite (-NO(2)), and carboxyl group (-COO) chelates in metal binding. The complete desorption of the cadmium was achieved by 0.1M H(2)SO(4) and 0.1M HCl. The C. procera based Cd(II) removal technology appears feasible.     

Growth and mineral accumulation in Eucalyptus camaldulensis seedlings irrigated with mixed industrial effluents

Effects of mixed industrial effluents on growth, dry matter accumulation and mineral nutrient in Eucalyptus camaldulensis seedlings were studied. The objective was to evaluate the adaptability of E. camaldulensis to effluent, tolerance to excess/deficiency of mineral elements and ultimately to determine suitable combinations of industrial/municipal effluent for their use in biomass production in dry areas. Different irrigation treatments were: T(1): good water; T(2): municipal effluent; T(3): textile effluent; T(4): steel effluent; T(5): textile effluent+municipal effluent in 1:1 ratio; T(6): steel effluent+municipal effluent in 1:2 ratio; T(7): steel+textile+municipal effluent in 1:2:2 ratio; and T(8): steel+textile effluent in 1:2 ratio. High concentrations of metal ions and low concentrations of Ca, Mg, K, Na, N and P in soil and seedlings of T(4) resulted in mortality of the seedlings within a few days. Addition of the textile/municipal effluent increased the survival time of the seedlings for two to three months in T(6), T(7) and T(8) treatments. Among the remaining treatments, the seedlings of T(2) attained 131 cm height, 1.97 cm collar diameter, 19 total branches and produced 158 g seedling(-1) of dry biomass at the age of 10 months. The seedling of T(3) produced the least growth and biomass. Growth equivalent to that of the seedlings of T(1) treatment was achieved when municipal effluent was mixed with textile effluent (T(5)). There was a decrease in soil pH, EC, SOC, NH(4)-N, NO(3)-N, PO(4)-P and basic cations and increase in the concentration of Cu, Fe, Mn and Zn with T(4) treatment. The reverse trend was observed in T(3) where a high concentration of Na might have reduced Mg and micronutrient concentration in seedlings potentially affecting root and leaf growth. Mixing of effluents may be useful in tree irrigation to increase biomass productivity, which is evidenced by improved growth in T(5) and survival in T(6), T(7) and T(8) treatments. Further, reduction of toxic concentration of metal ions in effluents may be helpful for a long-term field application.     

Delignification of Wheat Straw by Pleurotus spp. under Mushroom-Growing Conditions

Pleurotus sajor-caju, P. sapidus, P. cornucopiae, and P. ostreatus mushrooms were produced on unsupplemented wheat straw. The yield of mushrooms averaged 3.6% (dry-weight basis), with an average 18% straw weight loss. Lignin losses (average, 11%) were lower than cellulose (20%) and hemicellulose (50%) losses. The cellulase digestibility of the residual straw after mushroom harvest was generally lower than that of the original straw. It does not appear feasible to simultaneously produce Pleurotus mushrooms and a highly delignified residue from wheat straw.     

Bacteria reducing chromium in nature and in effluents of industrial plants

Bacteria capable of hexavalent chromium (Cr6+) reduction can be found in Cr6+-containing sewage and sediments of purification tanks of industrial plants. They cannot be detected in water and soil samples containing no chromium compounds. Bacteria reducing chromium belong to the genera Aeromonas, Escherichia, Pseudomonas and Enterobacter. Their activity of Cr6+ reduction correlates with the high resistance to the elevated content of this ion in the medium. The fine cell structure of these bacteria is described.     

Survival and chromate reducing ability of Pseudomonas aeruginosa in industrial effluents

The ability of a chromate-reducing Pseudomonas aeruginosa strain, isolated from tannery effluent, to survive and reduce chromate in the effluent of a tannery and an electroplating unit was evaluated. The test strain survived in the native tannery effluent but numbers fell sharply in the native electroplating effluent. Supplementation with a carbon (C), nitrogen (N) and phosphorus (P) source supported bacterial multiplication and chromate reduction in both types of effluents with almost equal efficiency. Chromate reduction, however, was not observed in the absence of C, N or P supplement, or in the chromate-reducing strain.     

Occurrence of Listeria spp. in effluents of French urban wastewater treatment plants

Listeria spp. were found in most treated waters (84.4%) and raw sludge (89.2%) of six French urban wastewater treatment plants and one composting facility, examined monthly over a 1-year period. Most strains belonged to Listeria monocytogenes, serotypes 4b/4e being predominant. Sludge composting and liming reduced or prevented Listeria contamination.