Extracellular enzymatic activities of cold-adapted bacteria from polar oceans and effect of temperature and salinity on cell growth

The potential of 324 bacteria isolated from different habitats in polar oceans to produce a variety of extracellular enzymatic activities at low temperature was investigated. By plate assay, lipase, protease, amylase, gelatinase, agarase, chitinase or cellulase were detected. Lipases were generally present by bacteria living in polar oceans. Protease-producing bacteria held the second highest proportion in culturable isolates. Strains producing amylase kept a relative stable proportion of around 30% in different polar marine habitats. All 50 Arctic sea-ice bacteria producing proteases were cold-adapted strains, however, only 20% were psychrophilic. 98% of them could grow at 3% NaCl, and 56% could grow without NaCl. On the other hand, 98% of these sea-ice bacteria produced extracellular proteases with optimum temperature at or higher than 35℃, well above the upper temperature limit of cell growth. Extracellular enzymes including amylase, agarase, cellulase and lipase released by bacteria from seawater or sediment in polar oceans, most expressed maximum activities between 25 and 35℃. Among extracellular enzymes released by bacterial strain BSw20308, protease expressed maximum activity at 40℃, higher than 35℃ of polysaccharide hydrolases and 25℃ of lipase.

Changs of Microorganisms in Mao Bamboo Stumps at Different Decomposition Degrees

The microbial flora in bamboo stump at different decomposition degree was studied. The results showed that the logarithmic values of bacterial concentrations ranged from 5.477 to 7.380; the logarithmic values of fungal concentrations ranged from 5.301 to 6.903; the logarithmic values of actinomycetes concentrations ranged from 5.740 to 7.000; the logarithmic values of cellulose-degrading bacterial concentrations ranged from 4.301 to 6.447; the logarithmic values of lignin-degrading bacterial concentrations ranged from 4.415 to 6.799. During the decomposition of bamboo stump, all the microorganisms grew rapidly at the initial stage; the logarithmic values of bacterial, fungal and actinomycetes concentrations changed constantly at the middle stage; and the logarithmic values were all higher at the late stage.There were assistance and competition among microorganism to certain extent. Understanding the decomposition rule of bamboo stump before its cutting down can provide some reference for the future decomposition of bamboo stump, and provide basic data for the isolation of microorganisms from bamboo stump at the species level.

Effects of Different Proportions of Spent Pleurotus ostreatus Substrate on Seed Germination and Seedling Growth of Mung Beans

[Objectives] This study was conducted to investigate the effects of different proportions of spent Pleurotus ostreatus substrate on the germination and seedling growth of mung beans. [Methods] The cellulose-degrading bacteria HB8 and HF1 were mixed with a commercially available microbial composting agent, respectively, for the composting of spent P. ostreatus substrate. Mung beans were cultivated with different proportions of spent mushroom substrate compost and soil. The seed germination rate, plant height, fresh weight and chlorophyll content of mung bean were used as indicators to investigate the effects of the organic fertilizer from spent P. ostreatus substrate on the growth of mung bean seedlings. [Results] The addition of cellulose-degrading bacteria can significantly improve the composting effect of the spent mushroom substrate. After 8 d of cultivation of mung beans with different ratios of the mushroom substrate organic fertilizer, 50% of the organic fertilizer can make the plant height, fresh weight and leaf chlorophyll content of mung bean seedlings reach the highest value and was suitable for mung bean breeding and cultivation. [Conclusions] This study provides scientific basis and technical indicators for the rapid and harmless treatment of spent mushroom substrate and its application in crop cultivation and nursery.