外源相容性溶质对S酵母耐盐性及酱油风味形成的研究

研究外源相容性溶质对S酵母(Zygosaccharomyces rouxii)耐盐性的影响,并探讨在高盐稀态酿造工艺中添加海藻糖对酱油风味的影响.结果表明,在酵母培养基中添加0.005mol/L海藻糖、甜菜碱和山梨醇,均可以显著改善S酵母在高盐培养基中的生长情况,缩短渗透胁迫条件下S酵母的延滞期,增加生物量,其中海藻糖的渗透保护效果最佳;添加海藻糖可使酱油的主体香味物质HEMF(4-羟基-2-乙基-5-甲基-3-呋喃酮)和乙酸乙酯的含量显著增加,同时促进S酵母合成酱油中典型风味物质4-EG (4-乙基愈创木酚).在酱油高盐稀态酿造中添加相容性溶质,如海藻糖,可有效改善酱油的风味和品质.     

高渗条件下相容性溶质对乳酸杆菌的作用

乳酸杆菌在发酵工业有着极其重要的作用,然而在乳酸杆菌高密度培养中却很难达到高的活菌数(一般活菌数在109 cfu/m L),这与其培养及生长过程中所处的环境有关。由于乳酸杆菌在高密度培养过程中往往通过流加碱液来消除酸的反馈抑制,而随之便会产生高渗应激问题,因此提出了相容性溶质的概念,在此就乳酸杆菌高渗应激反应及相容性溶质的作用等进行了简单的阐述和讨论。     

啤酒腐败微生物种类及特点

综述了啤酒中的微生物。着重介绍了啤酒生产原料中、生产过程中及二次污染的腐败微生物的种类、特性及其对啤酒危害。     

正渗透技术浓缩苹果汁过程中反向溶质扩散的研究

反向渗透扩散（RSF）是正渗透技术中的一大挑战,本实验立足于研究正渗透技术浓缩苹果汁性能以及功能性汲取液（乙酸钠、碳酸氢钠、柠檬酸钠溶液）的溶质扩散规律。首先,利用NaCl溶液为汲取液研究正渗透膜的基础特性,通过改变NaCl溶液浓度、进水流速以及膜操作模式,探究正渗透体系的水通量、反向溶质扩散及截留率,分析对去离子水和苹果汁的浓缩能力及溶质扩散规律;其次,对比不同功能性汲取液对苹果汁浓缩的效果和对RSF的影响,以期达到将RSF化弊为利的目的。结果表明,汲取液浓度和膜操作模式影响浓缩效率和RSF;采用压力延迟渗透（PRO）模式,苹果汁浓缩倍数和RSF均比正渗透（FO）模式高,PRO模式下,5 mol·L?1 NaCl汲取液RSF达87.34±6.32 g·m?2·h?1;不同种类功能性汲取液浓缩苹果汁的能力不同,汲水能力:碳酸氢钠>氯化钠>乙酸钠>柠檬酸钠。RSF:乙酸钠>碳酸氢钠>氯化钠>柠檬酸钠。2 mol·L?1柠檬酸钠汲取液的RSF为29.61±2.19 g·m?2·h?1,仅为同浓度NaCl汲取液的一半,与传统的NaCl汲取液相比,柠檬酸钠汲取液可有效控制RSF。     

乳酸菌在各种胁迫下的应激反应研究进展

乳酸菌在各种不同的环境下生长存活或者发挥作用,往往受到各种胁迫因素的影响和制约。各种胁迫包括盐、冷冻、热、干燥、酸胁迫等,它们在乳酸菌的生长、存储、保藏等过程中不可避免的会造成乳酸菌的损伤甚至死亡。本文综述了各种胁迫对乳酸菌的损伤机理并提出相应的保护措施来减少乳酸菌生理损伤,这也为乳酸菌直投发酵剂的制备提供了一定的理论依据。      

乳酸菌在各种胁迫下的应激反应研究进展

乳酸菌在各种不同的环境下生长存活或者发挥作用,往往受到各种胁迫因素的影响和制约。各种胁迫包括盐、冷冻、热、干燥、酸胁迫等,它们在乳酸菌的生长、存储、保藏等过程中不可避免的会造成乳酸菌的损伤甚至死亡。本文综述了各种胁迫对乳酸菌的损伤机理并提出相应的保护措施来减少乳酸菌生理损伤,这也为乳酸菌直投发酵剂的制备提供了一定的理论依据。     

鱼胶的种类、成分及功效研究进展

鱼胶是一种食药两用的滋补佳品,因突出的补充胶原蛋白、美容养颜、调节内分泌、提高免疫力等功效而备受消费者青睐。然而,目前国内外对鱼胶的研究较少且缺乏对消费者所关注问题的研究。为促进我国鱼胶产业持续发展,本文对市面上流行鱼胶的种类及特征,鱼胶的主要成分及功效,鱼胶产业发展所面临的问题进行系统综述,提出应加强对鱼胶的鉴别分类、功效、质量标准的研究,以期为鱼胶科学食用及产品开发提供参考。     

饺子馅的种类及调制

随着人民生活水平的不断提高,饺子这朵中华饮食百花园中的奇葩放射出更加夺目的光彩,它越来越多地出现在各种规格的宴席和一日三餐的饭桌上。 要做好饺子,关键是调馅。如何调好饺子馅呢?这除了考虑各地习俗的不同外,配料和调制是一项比较复杂的技术。 在琳琅满目的饺子馅中,各地有许多名品,但以咸味馅为多见。据有关资料统计,目前我国的饺子馅有几百种之多,故对饺子馅进行分类,为比较复杂。如按原料的性质来分,大体可分为荤馅、素馅和肉     

直链淀粉与支链淀粉相容性研究进展

直链淀粉和支链淀粉之间的相容性直接关系到淀粉类食品的加工性能、形态结构、储存性能以及食用性能等.然而在大多数情况下,直链淀粉和支链淀粉混合物都表现出不相容性,容易造成淀粉类食品的外观无光泽、口感差、淀粉易发生老化等不良现象.综述了近几十年来国内外有关对直链淀粉与支链淀粉相容性的研究现状,并简述了判断直链淀粉与支链淀粉相容性所采用的一些主要分析技术和方法,以便使各种分析技术和方法能更广泛而深入地应用于直链淀粉与支链淀粉相容性研究,为生产具有良好外观、流变学味觉和化学味觉以及良好稳定性的淀粉类食品提供理论指导.     

大蒜细胞溶质中超氧化物歧化酶的性质研究

利用热变性、等电点沉淀和DEAE -纤维素柱层析分离纯化大蒜细胞溶质中的超氧化物歧化酶 ,并对其性质进行了研究。结果表明 ,温度 40～ 6 0℃、pH4～ 9范围内酶的活性稳定 ,对KCN和H2 O2 敏感 ,紫外光区的吸收峰在 2 5 8nm ,可见光区的吸收峰在 6 80nm ,表明酶的类型为Cu·Zn SOD。     

Effects of yeast suspension density on the accumulation ratio of transported solutes

The previously described effect of cell suspension density on metabolic and transport phenomena in yeast, apparently caused by inhibition by dissolved carbon dioxide, is also observed with the accumulation ratio of both sugars and amino acids where not only a kinetic but also a energetic factor comes into play. Unlike all previously measured metabolic and transport parameters, the dependence of the accumulation ratio on suspension density is not monotonic but shows a pronounced maximum in the range of 4-8 mg dry wt/ml, depending on yeast species and on cultivation conditions. In Rhodotorula gracilis and in Lodderomyces elongisporus it is not due to CO2 but is semiquantitatively related to the proton-motive force across the plasma membrane as well as to the intracellular ATP content. It is observed both in oxygen and in argon, over a wide range of pH values and of temperatures, but it is suppressed by metabolic inhibitors. It is expressed only in a range of transported solute concentrations between about 0.1 and 10 mM.     

Effects of exogenous compatible solutes on growth of the hyperthermophilic archaeon Sulfolobus solfataricus

Six known compatible solutes as well as twenty L-amino acids were individually added to a glucose minimal medium and their effects on the growth of Sulfolobus solfataricus (DSM 1617) were examined. Among the compatible solutes tested, putrescine, trehalose, and l-glutamate enhanced the growth of S. solfataricus. On the other hand, glycine betaine, choline, and L-proline showed little or no influence on cell growth. When cells were grown in the glucose medium supplemented with trehalose or L-glutamate, S. solfataricus preferentially utilized the compatible solute over glucose. The growth-enhancement effect of L-glutamate was also observed to be dependent on the glucose concentration in the medium: growth enhancement was higher when the concentration of glucose was low and gradually decreased with increasing glucose concentration. Interestingly, the effects of amino acids on cell growth differed markedly depending on the chemical nature of the amino acid added. While acidic amino acids-L-glutamate and L-aspartate-enhanced the growth rate, almost no growth was observed in the presence of glycine, L-leucine, L-valine, L-phenylalanine, L-threonine, L-methionine, or L-cysteine. Among all the low-molecular-weight solutes tested in this study, the growth-stimulation effect was most profound in the presence of L-glutamate. When S. solfataricus cells were grown in a glucose (1.0 g/l) medium supplemented with 3.0 g/l L-glutamate, the maximal cell density and growth rate were about 3.2- and 2.3-fold higher than those obtained without L-glutamate.     

Long-range transported atmospheric pollutants in snowpacks accumulated at different altitudes in the Tatra Mountains (Slovakia)

Persistent organic pollutants (POPs), including polychlorobiphenyls (PCB), endosulfans, hexachlorocyclohexanes (HCHs), hexachlorobenzene (HCB), polybromodiphenyl ethers (PBDEs), and polycyclic aromatic hydrocarbons (PAHs), were analyzed in snowpack samples collected along an altitudinal gradient (1683-2634 meters above sea level) in the High Tatra Mountains (Slovakia). All analyzed compounds were found at all altitudes, pointing to their global distribution. The presence of PBDEs, particularly BDE 209, in the snowpack samples is especially relevant, as it reflects the air transport capacity of this low volatile, very hydrophobic pollutant to remote mountain regions. The most abundant compounds at all altitudes were PAHs, with mean values ranging from 90 to 300 ngL(-1), 1 order of magnitude higher than concentrations of other compounds. PCBs (sum of PCB 28, 52, 101, 118, 153, 138, and 180) and BDE 209 were the dominant organohalogen pollutants, with concentrations from 550 to 1600 pg L(-1) and from 670 to 2000 pgL(-1), respectively. Low brominated PBDEs, endosulfans, HCHs and HCB were consistently found in all samples at lower concentrations. The concentrations of these compounds correlated positively with altitude (i.e., negatively with temperature), which is consistent with cold-trapping effects. The regression coefficients were positive and statistically significant (p < 0.05) for all compounds except BDE 209, endosulfan sulfate, HCB and α-HCH. Contrariwise, the concentrations of BDE 209 and endosulfan sulfate exhibited a statistically significant positive correlation with total particle amount, which agrees with long-range atmospheric transport associated to aerosols according to the physical-chemical properties of these compounds. Snow specific surface area, which determines the maximum amount of each organic compound that can be sorbed by snow, proved utile for describing the distribution of the more volatile compounds, namely α-HCB and HCB, in the snowpack.     

葡萄品种学研究进展

文章系统分析了葡萄品种学研究的发展历史及现状，对研究内容的系统化、研究手段的现代化、数量化，研究方法的规范化作了详细论述。     

Growth of Escherichia coli ATCC 9637 through the uptake of compatible solutes at high osmolarity

The growth rate of Escherichia coli ATCC 9637 was determined in a chemically defined (CD) medium with high osmolarity, 1-1.2 M. The addition of ectoine or glycine betaine to the medium resulted in a significant stimulation of growth rate for this strain. In the presence of ectoine derivatives, hydroxyectoine and homoectoine, cell growth was not stimulated to the same extent as when ectoine was added, but it was improved slightly. The acceleration of growth rate of E. coli ATCC 9637 at elevated osmolarity was ascribed to the accumulation in the cells of ectoine or glycine betaine added to the medium, both of which were proved to be genuine osmolytes in cells. Rapid uptake of ectoine by cells was confirmed when ectoine was available in the CD medium with high osmolarity. Since strain ATCC 9637 did not accumulate ectoine in the absence of an energy source, ectoine uptake might take place not only through cellular sensing of the external high osmolarity but through cellular functioning via energization.     

Effect of compatible solutes on the respiratory activity and growth of Escherichia coli K-12 under NaCl stress

The respiratory activity of Escherichia coli K-12 was inhibited by high NaCl concentrations. The addition of compatible solutes such as proline and ectoine led to the recovery of the respiration of E. coli K-12 inhibited by 1 M NaCl to a similar extent as did the addition of glycine betaine. Glucose, an exogenous substrate for the stimulation of respiratory activity, was not taken up by the cells in the presence of 1 M NaCl, but active uptake of glucose was observed following the addition of compatible solutes. As a result, we obtained a good correlation between respiratory activities and glucose uptake rates, suggesting that the glucose uptake activity inhibited by high NaCl concentrations was facilitated by these solutes. The addition of proline did not lead to cell proliferation in the minimal medium containing 1 M NaCl, although the cells took up proline quite efficiently under high osmolarity. On the other hand, cell growth occurred after a lag time in the medium containing glycine betaine or ectoine in place of proline. Similar actions of the compatible solutes mentioned above were observed for E. coli ATCC 9637.     

可蓄积到食物中的持久性有机污染物及其检测技术研究进展

持久性有机污染物(POPs)可通过大气、水、土壤等介质在环境和人体积累,对人的身体健康和生命安全构成威胁。本文综述了持久性有机污染物的种类、危害和治理技术。详细介绍了目前检测方法的研究进展和热点,对各种方法的优缺点进行了分析。旨在为持久性有机污染物的检测提供参考。     

Production of poly-beta-hydroxybutyric acid by microorganisms accumulated from river water using a two-stage perfusion culture system

The perfusion culture system using a shaken ceramic membrane flask (SCMF) was employed to accumulate microorganisms separated from river water and to produce poly-beta-hydroxybutyric acid (PHB). Using a two-step culture method with a single SCMF, river microorganisms were cultured by separately feeding four representative carbon sources, n-propanol, lactic acid, methanol, and formic acid. After 140 h culture, the cell concentration and PHB content respectively reached 43 g/l and 35% when a propanol medium was fed. Using a two-stage perfusion culture with twin SCMFs, the seed cell mass was increased in the first SCMF and then supplied to the second flask for PHB production. As a consequence, the cellular PHB content rose to 51% in the second SCMF, while the cell concentration gradually increased to 25 g/l after 175 h perfusion culture. These results demonstrated the utility of the two-stage perfusion culture system for developing a cheap means of producing PHB coincident with wastewater treatment.     

液体深层发酵中丝状菌形态控制的研究进展

丝状菌广泛用于工业发酵,其菌丝形态与产物产量及发酵液粘度和能耗紧密相连,成为发酵过程控制的热点。本文综述了丝状菌形态特征、成球机理及液体深层发酵中影响丝状菌菌丝形态的因素,包括添加微粒子、碎布片及搅拌通气、接种量、培养基组分、培养条件等对丝状菌形态的影响,并对未来深层发酵丝状菌形态控制进行了展望。      

Reduction of carcass yield in transported pigs

Pigs (53-70 kg) in a non-fasted state were either not transported or subjected to a journey lasting for 1 h or 6 h prior to slaughter. Pigs given the short transport lost 0.6% and pigs given the long transport 2.3% of their initial live weight. After lairage for 1 h with access to water, all pigs were killed 8 h after their last feed. Compared with pigs not transported before slaughter, killing out percentage was slightly, but not significantly, lowered in the short transport group and significantly (P<0.05) reduced in the long transport group. The loss in carcass weight of the latter group amounted to 2.1% of the carcass weight of the untransported control pigs. Overall, killing out percentage and liver weight expressed as a percentage of liveweight were negatively correlated with the percentage loss of live weight in transport (P<0.02). The carcass weight loss on chilling was not influenced by treatment. Measurements of adrenal ascorbic acid suggested that most of the stress of transport occurred during the loading and first hour of the journey. Transported pigs drank more water in lairage, particularly those transported for 6 h which also had a higher total protein concentration in their plasma (P<0.05). Plasma creatine phosphokinase activity was not influenced by transport. It is suggested that enforced deprivation of water is an important contributing factor to the weight loss of pigs during transport but that physical activity is not.