食品抗菌包装系统的研究与展

由于人们对食品安全、货架期延长、成本效益、环境问题和消费便利性要求的提高,食品包装技术也得到了充分的发展,为了提高包装的性能,满足人们的需求,活性包装技术便应运而生.食品抗菌包装技术是活性包装技术的一种, 它可以有效地抑制食品表面的微生物,延长食品的货架期,保证食品品质.本文主要论述了抗菌包装技术类型以及它们在食品中的应用,并对抗菌包装系统中无机抗菌剂、有机抗菌剂和天然抗菌剂作了概括.最后,本文对抗菌包装技术未来发展趋势作了描述.     

共附生海洋微生物抗菌活性物质的研究

随着抗生素的广泛使用,微生物的抗药性逐渐增强.与此同时,环境污染的加剧,社会和人文的变迁,使人类的免疫力不断下降,新的致病菌和条件致病菌不断出现,这些已经成为严重的社会问题.解决问题的最有效办法就是加大力度,筛选开发新的抗生素.海洋拥有独特的生境条件,已成为新抗生素的重要来源.海洋微生物中共附生微生物具有独特的特点,已逐渐成为研究的焦点.     

食源性致病菌单细胞观测与预测的研究进展

微生物在单细胞水平下的生长普遍具有随机性和变异性,同时低菌量污染食品所造成的危害风险亦不可忽视,因此食源性致病菌单细胞的生长观测及预测研究逐渐成为食品预测微生物学及食源性致病菌风险评估的研究热点。在分析现有相关文献的基础上,将目前主要的食源性致病菌单细胞生长观测研究分为间接推断和直接观测两类方法;同时对食源性致病菌单细胞生长预测的模型参数与建模过程进行概述,比较了传统预测微生物的决定模型与微生物单细胞的随机模型二者之间的区别,强调了单细胞生长模型需在随机建模的基础上开展,并通过个体建模方法进一步联系其与所在食品环境之间的关系。最后,分析了食源性致病菌单细胞生长观测与预测的现状,并展望了其未来与食品安全风险评估相结合的发展趋势。     

Microbial dynamics in an anaerobic soil slurry amended with glucose, and their dependence on geochemical processes

Under anoxic conditions, microbial activities interact closely with geochemical reactions and consequently affect soils, underlying aquifers, and the atmosphere. Recent studies have noted the relationships between microbial biodiversity and environmental conditions, but the dynamics of numerous coexisting microbial groups in connection with soil biogeochemical processes has never been investigated. In this work, we investigated the dynamics of anaerobic microbial populations using a new method combining PCR-SSCP and epifluorescent direct counts, and analysed these results in the light of biogeochemical changes. Batch incubations were performed over an 8-day period on a calcic cambisol (WRB) incubated anaerobically, either without amendment (treatment C) or after adding glucose (treatment +G). In treatment +G, the predominant microbial processes included (i) NO₃⁻ and NO₂⁻ reduction during the first 12 and 24 h of incubation respectively, (ii) fermentations during the first 6 days with non-symbiotic N₂ fixation between days 1 and 6, enabling bacterial growth during this period, and probably (iii) reduction of FeIII by H₂ oxidation throughout the incubation period. In treatment C, microbiological and geochemical measurements revealed no prominent microbial activities, and the PCR-SSCP method led to complex bacterial density profiles without prominent peaks. In treatment +G, 78 microbial groups were distinguished; these were divided into seven sets (A to G) according to their dynamics. Bacteria belonging to sets A, E and F grew during the period of intense fermentation and were probably able to fix N₂, as is the case with Clostridium butyricum (set A). Bacteria belonging to sets B, D, and G were probably able to reduce FeIII to FeII with concomitant oxidation of H₂ into H₃O⁺, but unable to fix N₂. Two microbial groups in these sets were closely related to Clostridium favosporum (set B) and the genus Bacillus (set B). Bacteria belonging to class C were probably only able to reduce N oxide(s). Lastly, we obtained two similar estimates of the gross increase in microbial biomass by taking into account either (i) the sum of gross increases for the 78 microbial groups, or (ii) the energy yield of catabolic reactions minus the energy requirement for N₂ fixation.     

Ureolytic Activity of Soybean and Corn Residue Extracts

The enzyme urease is responsible for the rapid hydrolysis of urea in agroecosystems where more than 50% of the applied nitrogen (N) can be lost via ammonia volatilization. The objectives of the study were to (1) extract urease from corn (Zea mays L.) and soybean (Glycine max L.) and (2) compare the urease activity from soybean and corn residues to Jackbean (Canavalia ensiformis) urease using Fourier transform infrared spectroscopy (FTI-R). Concentrations of urea and sodium bicarbonate ranging from 0 to 200 mM were analyzed with FTI-R to determine the correlation to peak height. Bicarbonate produced the most responsive peaks to concentration at 1,362 cm^?1. Urease extracted from soybean residue was active, producing a bicarbonate peak at 1362 cm^?1, whereas no urease activity was observed in corn residue. Variation among urease activities in crop residues could suggest a need for more precise nitrogen management in conservation tillage agroecosystems to reduce ammonia volatilization.     

优化实验内容,改进教学方法,提高微生物学实验教学效果

微生物学实验是一门非常重要的基础课实验,在微生物学的教学中占有举足轻重的地位。通过合理地设置实验内容,采用科学的教学方法,提高了教学效果,培养了学生观察、思考、分析和解决问题的综合能力,为学生进一步学习有关专业课程打下良好基础。     

糠醛渣改良土壤增强苕子对盐碱土的适应性

科学合理的盐碱土改良措施对植物在盐碱土上适应性栽培具有重要的科学意义与应用价值。该研究旨在通过施用糠醛渣探讨盐碱土土壤特性及植物生长适应性栽培研究,为糠醛渣在盐碱土的合理使用提供科学依据。试验按土壤质量为基数确定糠醛渣的用量,试验由添加量0、5%、10%糠醛渣的盐碱土3个处理组成,温室条件下进行盆栽试验。结果表明,施用糠醛渣不仅降低盐碱土pH和含盐量,而且显著提升了土壤微生物多样性Sobs和Shannon指数,降低了simpson指数降低。主要表现在变形菌门(Proteobacteria)、放线菌门(Actinobacteria)、厚壁菌门(Firmicutes)和绿弯菌门(Chloroflexi)成为优势菌门。施用糠醛渣增加了苕子叶片中叶绿素、可溶性糖含量和脯氨酸含量。显著增强了过氧化物酶(POD)、过氧化氢酶(CAT)和超氧化物歧化酶(SOD)的活性。施用糠醛渣明显促进苕子生长发育,增加了苕子苗期生物量,5%糠醛渣用量处理改良盐碱土效果较优。研究表明糠醛渣通过改善盐碱土的其理化特性及生物多样性分布,促进苕子的生长发育,研究为糠醛渣在盐碱地土壤改良及植物适应性栽培的合理应用提供了科学依据与参考。     

Numbers of nitrate-reducing bacteria in the rumen as estimated by competitive polymerase chain reaction

Cell numbers of known species of nitrate- and nitrite-reducing bacteria, Selenomonas ruminantium, Veillonella parvula and Wollinella succinogenes , in the rumen of goats (25–30 kg) were estimated by competitive polymerase chain reaction (PCR). The number of S. ruminantium was the largest of the three species examined, and tended to be greater in goats fed a high-concentrate diet (5.6 × 10⁷ cells/mL rumen fluid) than in goats fed a high-roughage diet (1.3 × 10⁷ cells/mL). The number of V. parvula tended to be greater when goats were fed a high-roughage diet (6.7 × 10³/mL) than when fed a high-concentrate diet (3.2 × 10³/mL). The number of W. succinogenes was below the detectable level (< 1.0 × 10²/mL) when a high-concentrate diet was fed, but was significantly increased by feeding a high-roughage diet (1.6 × 10³/mL). Addition of potassium nitrate (6 g/day) to the high-concentrate diet tended to increase V. parvula , and significantly increased W. succinogenes , indicating that these two bacteria can be increased by feeding a diet containing nitrate.     

Enhancement of Nodulation and Yield of Chickpea by Co-inoculation of Indigenous Mesorhizobium spp. and Plant Growth–Promoting Rhizobacteria in Eastern Uttar Pradesh

We study the effect of plant growth–promoting rhizobacteria (PGPR) along with Mesorhizobium sp. BHURC02 on nodulation, plant growth, yield, and nutrient content of chickpea (Cicer arietinum L.) under field conditions. A similar study has been conducted for nodulation and plant growth of chickpea in pot experiment under glasshouse conditions. The treatment combination of Mesorhizobium sp. BHURC02 and Pseudomonas fluorescens BHUPSB06 statistically significantly increased nodule number plant^–1, dry weight of nodule plant^–1, and root and shoot dry weights plant^–1 over the control under a glasshouse experiment. The maximum significant increase in nodule number, dry matter, and nutrient content were recorded in co-inoculation of Mesorhizobium sp. BHURC02 and P. fluorescens BHUPSB06 followed by co-inoculation of Mesorhizobium sp., Azotobacter chroococcum, and Bacillus megatrium BHUPSB14 over uninoculated control in a 2-year field study. Hence, co-inoculation of Mesorhizobium sp. and P. fluorescens may be effective indigenous PGPR for chickpea production.     

微生物在环境保护中的应用及前景

从环境保护的角度出发,重点论述了微生物在这一领域的应用现状与发展前景,指出微生物将会在21世纪的环境保护领域中发挥重要作用。