砀山梨果醋加工工艺研究

优质梨果醋是以新鲜梨为原料,经液体深层发酵而成的优质调味品。以砀山梨为原料,经过对酒精发酵和醋酸发酵工艺的研究,得到了梨果醋。确定了混合菌种发酵的最佳比例,以及酒精发酵和醋酸发酵的最优发酵条件,对果醋产品混浊的原因及其澄清方法进行了研究。实验结果表明,制得的砀山梨果醋风味纯正,并具有水果香味,是一种价值较高的营养保健型果醋。     

酸乳发酵剂对羊乳发酵特性的研究

以羊奶粉为原料,选取4种由保加利亚乳杆菌和嗜热链球菌组成的乳酸菌基础发酵剂对羊乳进行发酵,通过测定发酵过程中羊乳的活菌数、酸度、pH值及黏度,研究这4种发酵剂的发酵特性.结果表明,在40 ℃条件下,YO-MIX499,YO-MIX300,FVV121,YO-MIX883四种基础发酵剂发酵羊乳,12～18 h活菌数达到最大值,分别为11.00×108,6.74×108,6.89×108,7.02×108 CFU/mL;酸度和黏度均随发酵时间的延长而增大,其中YO-MIX883产黏性最好,YO-MIX300产酸性最好.     

Germination of Salicornia bigelovii Ecotypes under Stressing Conditions of Temperature and Salinity and Ameliorative Effects of Plant Growth-promoting Bacteria

Salinity is a major stress condition. Salicornia bigelovii is a valuable edible halophyte, considered to be a promising resource for cultivation in arid coastal zones. Its productivity depends on the supplementary provision of nitrogen, for which an option is chemical fertilization. Nevertheless, indiscriminate use of chemical fertilizers contributes to the problem of increased salinity. The inoculation of plant growth‐promoting bacteria (PGPB) represents an alternative. Seed ecotypes from four coastal areas [Santa Rosa Chica, Santa Rosa Grande, Santa Cruz and Cerro Prieto (CP), Sonora, México] were collected, in order to inoculate them with two species of PGPB (Azospirillum halopraeferens and Klebsiella pneumoniae). Two germination tests were carried out to study the effect of salinity, temperature regime (night/day) and inoculation with PGPB on germination (percentage and rate), plant height, root length and biomass produced (fresh and dry matter). In the first test, all four ecotypes were considered, whereas in the second test only the CP ecotype was involved because it was found to be the outstanding ecotype in the previous test. Results showed inhibition of germination when salinity was higher in all ecotypes except CP. The CP ecotype showed a decrease of seed germination with an increase in NaCl concentrations at all temperatures tested. However, when it was inoculated with both PGPB, the germination percentage was influenced.     

菠菜内生固氮菌的分离及其功能特性研究

内生固氮菌具有促生、病原菌的防治及生物固氮等作用,并且占据着植物组织内有利于营养供应和微环境适宜的生态位,是重要的微生物菌种资源。从菠菜根内分离筛选优势内生固氮菌7株,其中假单胞菌属(Pseudomonas)5株,红球菌属(Rhodococcus)和黄杆菌属(Flavobacterium)各1株。菌株Pseudomonas sp.BCE6和Pseudomonas sp.BC-E8固氮酶活性较高,分别为(13.19±0.32)和(12.11±0.96)C2H4nmol/(mg protein·h),与圆褐固氮菌(ACCC11103)的固氮酶活性具有极显著性差异(P0.01);菌株Pseudomonas sp.BC-E7具有固氮酶活性[(8.42±0.03)C2H4nmol/(mg protein·h)]、产IAA能力[(59.58±4.15)μg/m L]、ACC脱氨酶活性[(5.067±0.376)μmol/(mg protein·h)],拮抗立枯丝核菌ACCC36124(Rhizoctonia solani)、麦类赤霉病ACCC36272(Gibberella zeae)等4种常见土传病害。菠菜内生固氮菌Pseudomonas sp.BC-E7是一株多功能内生菌,具有较好的生产应用前景。     

光合细菌在种植业上的应用研究近展

就光合细菌(PSB)在提高粮食、果蔬及多种经济作物的产量,并改善其产品质量,提高植物抗病毒能力,增强果实耐贮性,促进土壤有益微生物增殖,改善土壤理化结构,减轻农药对植物的毒害和降解残留农药中的作用等研究近况作了较全面的叙述,并对其作用原理作了简要分析。     

Screening of soil bacteria for plasmids carrying antibiotic resistance

Summary To evaluate the role of plasmids in soil communities antibiotic-resistant bacteria have been isolated from soil. Among them, 419 l-aminopeptidase positive strains (Gram-negative) and 28 l-aminopeptidase negative strains (Gram-positive) were screened for the presence of plasmids. None of the Gram-negative organisms contained plasmids. Among the Gram-positive bacteria plasmid-harboring strains were detected.     

Hydrogen oxidation activities in soil as influenced by pH,temperature, moisture,and season

Summary Hydrogen oxidation in soil was measured at low (1 ppmv) and high (300 ppmv) H₂ concentrations to distinguish between the activities of abiontic soil hydrogenases and Knallgas bacteria, respectively. The two activities also showed distinctly different pH optima, temperature optima, and apparent activation energies. The pH optima for the soil hydrogenase activities were similar to the soil pH in situ, i.e., pH 8 in an slightly alkaline garden soil (pH 7.3) and pH 5 in an acidic cambisol (pH 4.6–5.4). Most probable number determinations in the alkaline acidic soils showed that Knallgas bacterial populations grew preferentially in neutral or acidic media, respectively. However, H₂ oxidation activity by Knallgas bacteria in the acidic soil showed two distinct pH optima, one at pH 4 and a second at pH 6.4–7.0. The soil hydrogenase activities exhibited temperature optima at 35–40°C, whereas the Knallgas bacteria had optima at 50–60°C. The apparent activation energies of the soil hydrogenases were lower (11–23kJ mol^-1) than those of the Knallgas bacteria (51–145 kJ mol^-1). Most of the soil hydrogenase activity was located in the upper 10 cm of the acidic cambisol and changed with season. The seasonal activity changes were correlated with changes in soil moisture and soil pH.     

Utilization of Sparingly Soluble Phosphate by Red Clover in Association with Glomus mosseae and Bacillus megaterium

A pot experiment was conducted to investigate the mobilization of sparingly soluble inorganic and organic sources of phosphorus (P) by red clover (Trifolium pratense L.) whose roots were colonized by the arbuscular mycorrhizal (AM) fungus Glomus mosseae and in association with the phosphate-solubilizing (PS) bacterium Bacillus megaterium ACCC10010. Phosphate-solubilizing bacteria and rock phosphate had a synergistic effect on the colonization of plant roots by the AM fungus. There was a positive interaction between the PS bacterium and the AM fungus in mobilization of rock phosphate, leading to improved plant P nutrition. In dual inoculation with the AM fungus and the PS bacterium, the main contribution to plant P nutrition was made by the AM fungus. Application of P to the low P soil increased phosphatase activity in the rhizosphere. Alkaline phosphatase activity was significantly promoted by inoculation with either the PS bacterium or the AM fungus.