Comparative study on the productivity of strains of Pleurotus spp. in commercial cultivation

This paper describes the commercial production of two strains of Pleurotus pulmonarius, selected in the laboratory for their rapid mycelial development and high production of basidiomata, and one commercial strain of Pleurotus ostreatus. Substrate preparation, impact of pathogens and environmental conditions necessary for the production and quality of the fruiting bodies required are discussed.     

Siderophore production byBradyrhizobium spp. strains nodulating groundnut

EighteenBradyrhizobium spp. strains, fourRhizobium spp. strains and oneAzorhizobium caulinodans strain were grown under Fe limitation and assayed for siderophore production. It was further assessed if Fe accumulation in two groundnut cultivars was influenced by inoculant strain or nitrate fertilisation. Growth ofBradyrhizobium spp. strains nodulating groundnut was slow with mean generation times from 11–24 h. All strains, except MAR 967, showed a reduced growth rate when deprived of Fe; none of the strains showed starvation at 1 M Fe. In the CAS (chrome azurol S)-agar assay, all strains, which formed colonies, produced siderophores as visualised by orange halos around the colonies on blue plates.Bradyrhizobium strains produced much smaller halos than the referenceRhizobium meliloti strain. In the CAS-supernatant assay, all strains, except MAR 967, gave positive responses (measured as absorbance at 630 nm) when supernatants of Fe-depleted cultures were assayed with CAS-indicator complex in comparison with Fe-supplemented cultures. Responses of all fourRhizobium spp. strains were large, while responses of allBradyrhizobium strains, exceptB. japonicum MAR 1491 (USDA 110), were small and mostly insignificant. A small response, i.e. a low Fe-scavenging ability, implies either the production of small quantities of siderophores or the production of low affinity siderophores. Among theBradyrhizobium strains, MAR 1574 and MAR 1587 gave the largest responses taken over the two assays. Fe accumulation in groundnut cultivar Falcon was seven times larger than in cultivar Natal Common. No correlation was found between the quantity of nodule tissue and Fe accumulation, making it unlikely that bacteroids are involved in Fe acquisition by groundnuts. Nitrate-fertilised plants accumulated significantly more Fe, suggesting involvement of nitrate reductase in Fe assimilation in groundnut. The two most successful Fe-scavengingBradyrhizobium spp. strains were also the most effective in nodulating groundnut, the reverse also being true. Strain MAR 967, with the lowest Fe requirement, produced the largest nodule dry weight. These data indicate that improved Fe scavenging properties and/or reduced Fe requirement improve rhizospheric growth and with that nodulation effectiveness.     

The prospects for cryopreservation of noctuid eggs in the mass production of Trichogramma spp.

BioControl - Successful long-term cryopreservation of lepidopteran eggs for the mass production of parasitoids of the genus Trichogramma Westwood (Hymenoptera: Trichogrammatidae) requires a more...     

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.     

Comparative culturing of Pleurotus spp. on coffee pulp and wheat straw: biomass production and substrate biodegradation

The results of the cultivation of six strains of Pleurotus (P. djamor (2), P. ostreatus (2) and P. pulmonarius (2)) on coffee pulp and wheat straw are presented. Metabolic activity associated with biomass of each strain was determined, as well as changes in lignin and polysaccharides (cellulose and hemicellulose), phenolic and caffeine contents in substrate samples colonized for a period of up to 36 days. Analysis were made of changes during the mycelium incubation period (16 days) and throughout different stages of fructification. Greater metabolic activity was observed in the wheat straw samples, with a significant increase between 4 and 12 days of incubation. The degradation of polysaccharide compounds was associated with the fruiting stage, while the reduction in phenolic contents was detected in both substrates samples during the first eight days of incubation. A decrease was observed in caffeine content of the coffee pulp samples during fruiting stage, which could mean that some caffeine accumulates in the fruiting bodies.     

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。     

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。     

Aerobic hydrogen production by the heterocystous cyanobacteria Anabaena spp. strains CA and 1F.

Aerobic photoproduction of H2 was demonstrated in Anabaena spp. strains CA and 1F when cells were growing under nitrogen-fixing conditions. The rates of production, measured either by the hydrogen electrode or in a flow system by gas chromatography, were 10 to 15% of the rate of photosynthetic O2 evolution or 50 to 80% of the rates of acetylene reduction. Strains CA and 1F differed in several respects. In strain CA, H2 production was immediately partially sensitive to 3-(3,4-dichlorophenyl)-1,1-dimethylurea, whereas strain 1F was not immediately affected. Strain CA also showed a consistently higher rate of H2 production than did strain 1F. H2 production in strain CA was also markedly influenced by the light intensity used for growth, although the growth rates indicated that the light intensities used were essentially saturating.     

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。     

Diacetyl production by different strains of Lactococcus lactis subsp. lactis var. diacetylactis and Leuconostoc spp.

Summary Several strains of Lactococcus lactis subsp. lactis var. diacetylactis and Leuconostoc spp. were compared for product formation from citrate in milk cultures. Most strains produced acetoin and butanediol. Some strains derived from buffer starter cultures produced, in addition, -acetolactate. Lactococcus lactis strain C17, which produced acetoin and butanediol but no -acetolactate in culture, was compared physiologically with L. lactis strain Ru4, which produced only -acetolactate. Activities of enzymes involved in citrate metabolism were almost identical in both strains, with the exception of -acetolactate decarboxylase, which was missing in strain Ru4. The formation of -acetolactate, acetoin and diacetyl was further analysed in cell-free extracts. -Acetolactate synthase activity saturated at a high pyruvate concentration (100 mm). This is in agreement with the observed accumulation of pyruvate externally, and probably internally, during -acetolactate, acetoin and butanediol production by L. lactis cells.Correspondence to: J. Hugenholtz     

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.     

Cutinase production byStreptomyces spp.

Forty-fiveStreptomyces strains, including representatives of the plant pathogensS. acidiscabies, S. scabies, andS. ipomoea, were screened for ability to produce enzymes (cutinases) capable of hydrolyzing the insoluble plant biopolyester cutin. Initially, all strains were tested for production of extracellular esterase in liquid shake (250 rpm) cultures at room temperature in defined (glycerol-asparagine) or complex (tryptone-yeast extract with or without addition of mannitol) broth media supplemented with either tomato or apple cutin. Esterase activity was determined by a spectrophotometric assay utilizing the model substratep-nitrophenyl butyrate. Of the five strains exhibiting highest esterase activity, four (S. acidiscabies ATCC 49003,S. scabies ATCC 15485 and IMRU 3018, andS. badius ATCC 19888) were confirmed to produce enzymes with cutin-degrading activity (cutinases). Confirmation of extracellular cutinase production was accomplished by use of a new high-performance liquid chromatography method for separation and quantification of released cutin monomers. Monomer identification was confirmed by GC/MS analyses. Cutinase production was induced 2- to 17-fold by inclusion of cutin in the media. To our knowledge this constitutes the first report of cutinase production byStreptomyces spp. other thanS. scabies.Reference to any brand or firm name does not constitute endorsement by the U.S. Department of Agriculture over others of a similar nature not mentioned.     

Differences in production of several extracellular virulence factors in clinical and food Aeromonas spp. strains

C. PIN, M.L. MARÍN, D. SELGAS, M.L. GARCÍA, J. TORMO AND C. CASAS. 1995. Production of several extracellular virulence factors (lipase, protease and haemolysin) was compared in 15 Aeromonas spp. isolated from faeces of patients with Aeromonas -associated gastroenteritis and 81 strains isolated from food. Strains from food did not show differences in production of these factors when compared with strains isolated from faeces. However, if strains were considered in relation to autoagglutination (AA) character, the AA⁺ differed from AA^- strains in lipase and protease production. Supernatant fluids of AA⁺ food and human strains showed 2·5-fold more protease production than that observed in AA^- strains. These two characteristics of certain Aeromonas strains could be related with the more virulent capacity.     

Treatment of coloured industrial effluents with Pleurotus spp

The decolouration of fermentation residues (vinasse) and liquid extract of coffee pulp by the mushroom Pleurotus ostreatus was studied in addition to laccase activity. The fungus was inhibited in both residues when they remained undiluted. In submerged cultivation on wastewaters a good production of biomass (14.8 g/l for vinasse and 5.4 g/l for extract of coffee pulp) and also laccase activity (14.1 U/ml for vinasse and 3.0 U/ml for extract of coffee pulp) up to the 10 days of fermentation was observed, being significantly greater in the culture with vinasse. It was shown that treatment with this mushroom reduces both the chemical oxygen demand and the colour, contributing to their biological treatment.     

Onchocerca spp: cryopreservation of microfilariae and subsequent development in the insect host.

Microfilariae of Onchocerca gutturosa, O. cervicalis and O. volvulus were successfully recovered after freezing, storage at ?196 C, and thawing. The technique that produced maximum viability involved a two-step cooling schedule consisting of an initial slow cool of 1 C min^?1 to an intermediate temperature of between ?14 and ?17 C, followed by a rapid cool into liquid nitrogen (taking about 1 sec). Upon rapid warming to 37 C, a high percentage of microfilariae showed normal motility. Following subcutaneous injection into T.O. mice, the microfilariae of O. gutturosa migrated to the skin of the ears and nose, and a proportion of them developed into third-stage larvae in the insect vector, Simulium ornatum. Microfilariae of O. volvulus also developed into third-stage larvae in this insect, while those of O. cervicalis developed similarly in their natural vector, Culicoides nubeculosus. This technique of preservation provides a good and reliable method for storage of viable microfilariae of these bovine, equine, and human Onchocerca spp.     

Evaluation of the effect of temperature and nutrients on the survival of Campylobacter spp. in water microcosms

Batch microcosms containing various water types (de-ionized and river water with or without sediment), incubated at a range of temperatures (5-37 degrees C), were used to facilitate a comparative evaluation of the significance of such variables and their interactions upon the collective and individual survival of four species of thermophilic Campylobacter. All variables significantly influenced (P < = 0.031) population decay rates. Minimal decay for the group was identified at low temperatures (5 degrees C) in river water, i.e. nutrient-containing microcosms. Collective decay rates within river water microcosms were significantly decreased (P = 0.03) from those observed in de-ionized water, particularly at environmental temperatures (5 and 15 degrees C). However, the increased nutrient levels observed in sediment-containing microcosms did not significantly (P = 0.41) reduce population decay rates. Overall, Camp. jejuni populations demonstrated the most resilience to the environmental stressors evaluated, with the exception of 15 degrees C where Camp. lari was the most persistent. Campylobacter coli and Camp. upsaliensis demonstrated comparable survival characteristics but were less resilient than Camp. jejuni and Camp. lari. These observations identify the suitability of water systems as a reservoir and medium for Campylobacter infection, and potentially identifies Camp. jejuni and Camp. lari as the main protagonists of water-mediated campylobacteriosis.     

Effect of substrate particle size and additional nitrogen source on production of lignocellulolytic enzymes by Pleurotus ostreatus strains

Two strains of Pleurotus ostreatus (IE-8 and CP-50) were grown on defined medium added with wheat straw extract (WSE). Mycelia from these cultures were used as an inoculum for solid fermentation using sugar cane bagasse (C:N=142). This substrate was used separately either as a mixture of heterogeneous particle sizes (average size 2.9 mm) or as batches with two different particle sizes (0.92 mm and 1.68 mm). Protein enrichment and production of lignocellulolytic enzymes on each particle size was compared. The effect of ammonium sulphate (AS) addition was also analyzed (modified C:N=20), this compound favored higher levels of protein content. Strain CP-50 showed the highest increase of protein content (48% on particle size of 1.68 mm) when compared to media with no additional N source. However, strain IE-8 produced the highest levels of all enzymes: xylanases (5.79 IU/g dry wt on heterogeneous particles) and cellulases (0.18 IU/g dry wt on smallest particles), both without the addition of AS. The highest laccase activity (0.040 IU/g dry wt) was obtained on particles of 1.68 mm in the presence of AS. Since effect of particle size and addition AS was different for each strain, these criteria should be considered for diverse biotechnological applications.     

Isolation of spontaneous mutant strains of Flavobacterium spp.

Flavobacterium sp. ATCC 27551 is prototrophic, streptomycin-resistant and contains plasmid DNA. Two strains of this Flavobacterium sp. with altered growth requirements and antibiotic sensitivity have been isolated. Unlike the parental strain, both isolates are sensitive to the antibiotic streptomycin. Isolate YE requires yeast extract supplementation of the medium and contains no plasmid DNA. Isolate AHC contains plasmid DNA and requires aspartic acid, histidine and cysteine for growth.