In this paper,a slight halophilic alkaliphile swain,Alkalibacterium sp.F26,which produced high level of intracellular CAT observed in previous research,was selected as a model microbial to explain the responses of this bacterium to oxidative stress.The results indicated that Alkalibacterium sp.F26 had obvious responses to higher concentration (＞1 mmol/L) of H2O2 than that to lower H2O2 (＜1 mmol/L) challenge from the aspects of defensive enzyme synthesis and cofactors level variation.As for catalase production,the activity increased up to 106.54 U/rag protein which was 1.76 fold of the control when cells were challenged by 3 mmol/L H2O2,but its activity only was 1.13 fold when H2P2 was 100 μmol/L.As far as energy state was concerned,ATP production and NAD+ generation were significantly inhibited from 20.55 μmol/L to 17.80 μmol/L and 69.89 μmol/L to 31.77 μmol/L,respectively,leading to the drop of energy charge from 0.77 to 0.68 and the increase of the portion of NADH/NAD+ from 0.08 to 0.41 in the former case.However,these effects were less distinct under lower concentration of H2O2.Except of the condition of 100 μmol/L H2O2,under which the activation of defensive mechanism resulted in an increase of ATE the level of ATP dropped from 22.69 μmol/L of the control to 22.38 μmol/L and 13.70 μmol/L when challenged by 50 μmol/L and 500 μmol/L H2O2.Besides,the concentration of NADH fluctuated and the NAD+ gradually reduced when H2O2 below 1 mmol/L.

Endophytic bacteria reside in most healthy plants;it can not be easily influenced by outer environment.Some endophytic bacteria are beneficial to host plants,such as growth promotion,disease prevention and nitrogen fixation etc.Therefore,endophytic bacteria ale the potential microbial fungicides,it may be widely applied.In this study,endophytic bacteria were isolated from soybcan cultivar Hefeng 25 that was a main soybean cultivar in Heilongjiang province,China.The results indicated that the density of endophytic bacteria varied in different tissues of the plant.It was 3.4×103CFU/g in roots,2.8×103CFU/g in leaves,2.9×102 CFU/g in stems and 1.4×102 CFU/g in seeds.The activity of 121strains against Fusarium oxysporum f.sp.soybean,caused soybean root rot,were assayed.25.6% of them showed antagonistic activity against F. oxysporum f. sp.soybean.One of them,strain TF28 isolated from soybean roots could inhibit the growth of many fungal pathogens.The inhibitory rates against F. oxysporum from different plant species were 80.2%-96.7%.Based on the morphological,physiological and biochemical characteristics as well as the sequence of 16S rRNA,strain TF28 was identified as Bacillus amyloliquefaciens.

astaxanthin is an effective antioxidant and natural pigment which has wide application. Phaffia rhodozyma is a good source of astaxantin, but wild strain has limited use in industry because of low production level of astaxanthin. Several mutants of Phaffia rhodozyma were obtained by exerting mutagen N-methyl-N-nitro-N-nitrosoguanidine. The growth curve suggested that pigments were mainly produced in the middle and latter periods of log phase. The pigments were extracted from Phaffia rhodozyma and analysed by esterification, thin layer chromatography and absorption spectrometry. It was proved that astaxanthin, astaxanthin diester and β-carotene were the major components of the pigments produced by Phaffia rhodozyma. We also studied the pigments producing phase of Phaffia rhodozyma. and founded that astaxanthin was stable to light under butylatedhydroxytoluene coexistance.

Four cellulolytic strains, which can be used as feed additive, were studied under the conditions of various temperature, incubation time, and anaerobic process, and examined the changes of their cell protein content, cellulase and hemi-cellulase activity. The results show: 1) The maximum cellulolytic enzyme activities were observed incubation 20h; 2) Constant medium temperature 28℃ was adequate to the growth of the 4 strains ; 3) anaerobic condition, 39℃±2℃ and fermentation 12h, 24h, 36h, the tested strains can growth well in PDA plate, however, the cellulolytic enzyme activities and growth of the tested strains were influenced adversely when fermentation 48h. The experiment provide many important basis for the strains production, storage and utilization.

Four bacterial and 8 fungal isolates were incubated in media for 6 days. It was found that organic acid content in the media increased largely, but pH decreased sharply. Phosphorus content in the media enhanced dramatically as well. The fungal isolates showed stronger ability to dissolve phosphate rock than the bacterial ones. These isolates excreted not only quite distinct volume of organic acids but diverse organic acid chemicals. The fungi produced more kinds of organic acids than the bacteria. However, there was no significant relationship between the total quantity of organic acids and P content in the media.

Six atrazine-degrading strains, Pseudomonas spp. AD1, AD2, AD6, Agrobacterium sp. AD4, Xanthomonas AD5, and Erwinia sp. AD7, were isolated from industrial wastewater. These strains are able to grow on atrazine as sole nitrogen source. Strain AD1 is able to degrade atrazine of 0. 3g/L in minimal medium at a percentage of 99.9% in 72 hours. PCR products that are homologous to the atrazine chlorohydrolase gene atzA)from Pseudomonas sp. strain ADP were obtained by PCR method using total DNA of the strains AD1 ,AD4,AD5,AD6,and AD7 as templates.

The enzyme activity of α－Acetolactate Decaroboxylases (ALDC)from different microbes was studied, the results demonstrated that it was quite different among them. There were diversities of their enzyme reaction velocities. It was clear that the enzyme activity was affected by the pH of the enzyme reaction system, for example, the optimum pH of ALDC from Lactococcus lactis was 6.6, while for Aerobacter Aerogenes it was 5.8. Addition leucine,valine and isoleucine into enzyme reaction system obviously affected the enzyme activity of ALDC from different microbes.

We first find Xanthomonas campestris N. K-01 which don't produce xanthan at 28℃ cansynthesize and secrete the xanthan under low temperature (4℃). Little string is the most minute unit of the secreted under low temperature. Many little strings ecreted by bacterium cell extend to form a wider xanthan fiber. When depart from cell, xanthan fiber either twine to form double helix of bundle together. They are both advanced structures of the xanthan strings. Xanthan secreted under 4℃ has the same chemical composition and structure as that under 28℃, but lower moleculer weight and lower pyruvate content.

The present study is concerned with the isolation and screening of different strains of Aspergillus oryzae for the production of alpha amylase. Ninety strains were isolated from soil and tested for the production of alpha amylase in shake flasks. Of all the strains tested,Aspergillus oryzae GCB-32 and Aspergillus oryzae GCB-35 gave maximum production of alpha amylase. Different culture media were screened for maximum production of alpha amylase by both the strains Aspergillus oryzae GCB-32 and Aspergillus oryzae GCB-35. Kinetic analysis revealed that the values of product yield coefficient (Yp/x) and specific product yield coefficient( qp ) were found highly significant (p ≤ 0.05 ) when medium M1 was used for the enzyme production.

Pseudomonas aeruginosa recognized as opportunistic pathogen causes severe infections for hospitalized patients, survive in and resist many antimicrobial agents like antibiotics and disinfectants. The aim of this study is to evaluate the role of EDTA in improving the sensitivity of resistant P. aeruginosa strains to disinfectants and Na-citrate. The strains used in this study were selected in house from Tanta University hospital, Egypt and tested for the synergistic effect of EDTA with Na-citrate or disinfectant (s). The results showed a significant effect ofEDTA in improving P. aeruginosa sensitivity. In conclusion, we proposed that using EDTA in combination with different sanitization compounds and antimicrobial agentsespecially in hospitals aiming to control the spreading of infections.