双歧杆菌耐氧菌株的筛选及应用

从婴儿粪便中分离出一株厌氧性无芽孢杆菌，经属和种的鉴定，为长双歧杆菌。经长期耐氧驯化，此菌由厌氧生长驯化成有氧生长良好的菌种，与乳酸菌混合发酵后，可制成口感细腻、气味醇和、酸甜适口，有很好的营养保健功能的双歧杆菌酸奶。     

青春双歧杆菌的耐氧驯化及不同低聚糖对其增殖效果的影响

为改善青春双歧杆菌在发酵产品中活菌数低、菌种功效弱的情况,对厌氧青春双歧杆菌进行耐氧驯化,采用无氧有氧交替驯化法,在驯化过程中逐渐增加青春双歧杆菌培养液的氧分压,测定青春双歧杆菌驯化前后生理特性,并对比大豆低聚糖、低聚木糖、低聚麦芽糖对青春双歧杆菌增殖的影响。结果表明,青春双歧杆菌在耐氧驯化后对氧气的敏感程度下降,有氧条件下生长能力达标,产酸能力得到提升,菌体驯化前后形态基本一致,耐氧青春双歧杆菌代谢产生的乙酸与乳酸比值较厌氧青春双歧杆菌更适宜发酵,在3种低聚糖中,低聚木糖对青春双歧杆菌增殖作用明显,可作为青春双歧杆菌良好的双歧因子。耐氧驯化后的青春双歧杆菌有着优良的生理特性,能够作为潜在的益生菌菌种深入研究其功能并可应用于发酵食品中。     

双歧杆菌厌氧培养及耐氧驯化的研究

用４种不同驱氧方式的缸内厌氧法培养双歧杆菌，比较其厌氧培养效果。对厌氧的双歧杆菌进行耐氧驯化，耐氧化明显提高，经生理鉴定证明，驯化后的菌株与未经驯化的菌株相比，生理学特性没有发生变化。     

纯双歧杆菌酸奶的研究

将双歧杆菌经过筛选驯化使其岈厌氧驯化成有氧生长良好的菌种，制作纯双歧杆菌酸奶。Ｃ４菌可在牛乳中有氧条件下生长良好，而且品味优良，成本不高，设备简单，不需添加酸奶菌种即可制得纯双杆菌酸奶。     

双歧杆菌体外增殖培养的初步研究

本文主要研究了婴儿双歧杆菌的厌氧培养方法、碳源、氮源以及一些生物材料提取物对婴儿双歧杆菌体外增殖的影响。实验结果，盐水瓶培养法是婴儿双歧杆菌厌氧培养的最好方法；乳糖、大豆蛋白胨分别是婴儿双歧杆菌生长适宜的碳源和氮源；玉米、羊栖菜和马尾藻提取液能显著促进婴儿双歧杆菌生长；羊栖菜提取液分别与玉米提取液、酵母膏配合能进一步促进婴儿双歧杆菌的生长。     

双歧杆菌体外增殖培养的初步研究

本文主要研究了婴儿双歧杆菌的厌氧培养方法、碳源、氮源以及一些生物材料提取物对婴儿双歧杆菌体外增殖的影响.实验结果,盐水瓶培养法是婴儿双歧杆菌厌氧培养的最好方法;乳糖、大豆蛋白胨分别是婴儿双歧杆菌生长适宜的碳源和氮源;玉米、羊栖菜和马尾藻提取液能显著促进婴儿双歧杆菌生长;羊栖菜提取液分别与玉米提取液、酵母膏配合能进一步促进婴儿双歧杆菌的生长.     

动物双歧杆菌乳亚种BZ11的耐氧驯化及降胆固醇性能的研究

为了提高动物双歧杆菌乳亚种BZ11对有氧环境的耐受性,采用逐渐增加培养基中的氧分压和有氧、厌氧条件下交替培养两种方案对其进行了耐氧驯化。通过对驯化前后菌株的生长特性进行分析得出逐渐增加培养基中的氧分压的驯化方案取得了更好的效果。经最优方案驯化后的菌株在有氧条件下培养20 h后,活菌数可达到6.30×10~8CFU/m L,是初始菌株的2.24倍。驯化后菌株的降胆固醇率为27.31%±0.80%,与初始菌株相比没有显著性差异(P0.05)。通过鉴定得出,动物双歧杆菌乳亚种BZ11在耐氧驯化前后保持了相似的形态及生理生化特征。因此,驯化后的菌株有望作为1株潜在益生菌被开发利用。     

菊芋在体外对双歧杆菌生长的影响研究

目的:研究菊芋在体外对双歧杆菌生长的影响,为进一步开发菊芋资源和生产双歧杆菌制品提供理论依据。方法:以菊芋汁为试验材料,以长双歧杆菌(Blm)和两歧双歧杆菌(Bbm)为试验菌株,采用Hungate厌氧培养技术。结果:菊芋汁在基础培养基中对双歧杆菌具有促进生长作用,表现为生长速率提高,最大生长量增加,并且对不同菌种的促进生长作用存在差异。结论:菊芋在体外对双歧杆菌有促进生长作用。     

耐氧性双歧杆菌的驯化及其培养条件的研究

通过对一株青春双歧杆菌的耐氧驯化,获得了具一定耐氧能力的双歧杆菌ad,该菌株可在含有一定空气容积的密闭容器中良好生长。并探讨了以大豆为主要原料发酵培养青春双歧杆菌ad的工艺条件,其最佳培养基配方为:豆浆浓度3BX,葡萄糖1%,自制乳肽0.5%,番茄汁2.5%,胡萝卜汁2.5%;pH7.0;接种量2%;培养温度37℃;厌氧培养24～48h。发酵液活菌数可达6.9×109cfu/mL。青春双歧杆菌ad发酵液原液直接冷冻干燥,无须添加其他保护剂;双歧杆菌ad冻干前增加温度前处理环节,可提高菌体成活率;双歧杆菌ad含水冻干粉活菌数达1.0×1010cfu/g;绝干样品活菌数达1.1×1010cfu/g。     

双歧杆菌最佳培养条件的研究

双歧杆菌是人体最重要的生理细菌之一，它是一种专性厌氧微生物。根据双歧杆菌生理生化特性，选择了5种营养丰富且对该茵体生长有利的培养基进行研究。研究结果：发现最佳培养基为淀粉水解液培养基，最佳温度为37℃，最适pH值为7，最佳培养时间为12h。     

微冻及真空包装对原汁整壳贻贝贮存期品质的影响

为研究微冻及真空包装对原汁整壳贻贝贮存期品质的影响,将原汁整壳贻贝进行真空包装及普通包装,于4和-3℃下进行贮存,对样品的感官评分、汁液流失率、pH、电导率、挥发性盐基氮(total volatile basic nitrogen,TVB-N)、2-硫代巴比妥酸(2-thiobarbituric acid,TBA)、菌落总数等指标的变化规律进行分析。结果表明:原汁整壳贻贝在贮藏过程中,随着时间的延长,感官评分下降;pH先降低后升高;汁液流失率、TVB-N、TBA、电导率和菌落总数均随贮存时间的延长而增长。-3℃微冻的保鲜效果明显优于4℃冷藏(P<0.05),真空包装的保鲜效果明显优于普通包装(P<0.05),-3℃微冻结合真空包装保鲜效果最佳,能显著延缓原汁整壳贻贝感官性状的下降(P<0.05),抑制汁液流失率、电导率、TVB-N值、TBA值的上升(P<0.05),延缓pH最低点出现的时间(P<0.05),抑制菌落总数的增长(P<0.05)。综合比较分析,4℃普通包装、4℃真空包装、-3℃普通包装、-3℃真空包装的货架期分别为6、15、15和60 d。因此,微冻结合真空包装能较好维持原汁整壳贻贝的感官性状及品质稳定性,有效延长货架期。     

In vitro effects of the thiopeptide A10255 on ruminal fermentation and microbial populations.

Experiments used unadapted mixed cultures of ruminal microorganisms in batch or continuous culture fermentation to investigate the effect of a thiopeptide, A10255, on ruminal fermentation and microbial populations. After 24 h of fermentation in batch culture, addition of A10255 (.5 to 20 ppm of the culture fluid) to 0, 45, 60, and 75% concentrate diets had no effect on total VFA but increased molar proportion of propionate and decreased butyrate. The molar proportion of acetate was decreased by treatment only in the 0 and 75% concentrate diets. The increase in molar proportion of propionate by 20 ppm of A10255 was less than the increase caused by a similar concentration of monensin. The same concentration of A10255 (20 ppm) decreased ADF digestion less than 20 ppm of monensin. In continuous culture, A10255 (33 mg/kg of dietary DM) did not affect total VFA concentration, culture pH, OM digestion, or ADF digestion. Ruminal bacterial populations of total anaerobes and lactate-producing, lactate-utilizing, cellulolytic and amylolytic bacteria were unaffected by treatment. However, molar proportions of acetate, butyrate, and isovalerate were decreased, and propionate was increased, by addition of A10255.     

Development of a fed-batch culture process for enhanced production of recombinant human antithrombin by Chinese hamster ovary cells

Antithrombin is a serine protease inhibitor that inactivates several coagulation proteases, primarily thrombin and factor Xa. The Chinese hamster ovary (CHO) cell line transfected with a vector expressing recombinant human antithrombin (rAT) and a selectable marker, glutamine synthetase (GS), was cultivated in a 2-l fed-batch culture process using serum-free, glutamine-free medium. To maximize the rAT yield, effects of culture pH, balanced amino acid feeding, and an increased glutamate concentration on cell metabolism and rAT production were investigated. When cells were grown at pH values of 6.6, 6.8, 7.0, and 7.2, the maximum cell density and maximum lactate concentration decreased with decreasing pH. The highest production level of rAT was obtained at culture pH 6.8 due to the extended culture lifetime. Compared to the imbalanced amino acid feeding at culture pH 6.8, the balanced amino acid feeding increased the amount of rAT activity by 30% as a result of an increased viable cell number. A decrease in the specific glucose consumption rate (q(Glc)) with increasing culture time was observed in all the above-mentioned experiments, while the glucose concentration was maintained above 0.7 g l(-1). In addition, a decrease in the specific rAT production rate (q(rAT)) was observed after the depletion of lactate in the late cultivation stage. Taken together, these results suggest that the reduced availability of cellular energy caused by the decrease in q(Glc) and depletion of lactate led to the decrease in q(rAT). This decrease in q(rAT) was partially prevented by increasing the residual glutamate concentration from 1 mM to 7 mM, thus resulting in an additional 30% increase in the amount of rAT activity. The optimized fed-batch culture process yielded 1.0 g l(-1) rAT at 287 h of cultivation.     

Effects of Lactobacillus plantarum and Staphylococcus xylosus on the Quality Characteristics of Dry Fermented Sausage "Sucuk"

ABSTRACT:  The effect of starter culture, containing the strains Lactobacillus plantarum GM77 and Staphylococcus xylosus GM92, isolated from traditional sucuk, on the quality characteristics of dry fermented sausage (sucuk) during ripening period was studied. The microbiological (lactic acid bacteria, Micrococcus/Staphylococcus , Enterobacteriaceae) and physicochemical (pH, a_w, NPN, TBARS) properties and volatile compounds, extracted by solid phase microextraction and analyzed by gas chromatography-mass spectrometry, were determined in sucuk samples with starter culture and in the control group (without starter culture). Both starter culture and ripening period had significant effects on lactic acid bacteria, Micrococcus/Staphylococcus counts, and pH and a_w values ( P  < 0.01). The highest value for nonprotein nitrogen (NPN) was observed to occur in samples with starter culture ( P  < 0.05). TBARS value increased during ripening, the highest value was determined at 14th day in samples with starter culture. Among volatile compounds, terpenes were the major group in sucuk. Other volatile compounds (aldehydes, ketones, sulfur compounds, acids, esters, aliphatic hydrocarbons, aromatic hydrocarbons, and alcohols) can be found in fewer amounts. While the use of starter culture was affecting a few compounds, ripening period had affected most of the compounds.     

Interactive Effects of Factors Affecting Gelation of Whey Proteins

The individual effects of heating time (15–120 min), pH (3–9) and NaCl (0–2M), sucrose (0–30% w/v) and protein (10–30% w/v) concentrations on the strength, turbidity and water holding capacity were investigated on a commercial whey protein concentrate (WPC, 75% protein) when heated at temperatures ranging from 65 to 90°C. Interactive effects were investigated using a four-variable, five-level central composite rotatable design (CCRD) analyzed by response surface methodology (RSM). Gel strength (GS) and water holding capacity (WHC) increased with protein concentration, heating temperature and time. Increasing sucrose concentration decreased GS but increased WHC. Increasing NaCl concentration increased GS and WHC below pH 5 but resulted in weaker gels at high pH (>7).     

Enhanced biohydrogen production from sewage sludge with alkaline pretreatment

Batch tests were carried out to analyze influences of the alkaline pretreatment and initial pH value on biohydrogen production from sewage sludge. Experimental results of the impact of different initial pH on biohydrogen production showed that both the maximal hydrogen yield occurred and that no methane was detected in the tests of at the initial pH of 11.0. The final pH decreased at the initial pH of 7.0-12.5 but increased atthe initial pH of 3.0-6.0, probably due to the combination of solubilized protein from sludge and the formation of volatile fatty acids (VFAs) and ammonia during biohydrogen fermentation. The performance of biohydrogen production using the raw sludge and the alkaline pretreated sludge was then compared in batch fermentation tests atthe initial pH of 11.0. The hydrogen yield was increased from 9.1 mL of H2/g of dry solids (DS) of the raw sludge to 16.6 mL of H2/g of DS of the alkaline pretreated sludge. No methane and less carbon dioxide (0.8% of control) were present in the biohydrogen production from the alkaline pretreated sludge. These results clearly showed that biohydrogen production could be enhanced and maintained stable by the combination of the high initial pH and alkaline pretreatment. The mechanism of biohydrogen production from sewage sludge at high initial pH was therefore investigated because the results of this study were differentfrom previous studies of biohydrogen production. Results showed that protein was the major substrate for biohydrogen production from sewage sludge and that Eubacterium multiforme and Paenibacillus polymyxa were the dominant bacteria in biohydrogen production from alkaline pretreated sludge at an initial pH of 11.0. The combination of alkaline pretreatment and high initial pH could not only maintain a suitable pH range for the growth of dominant hydrogen-producing anaerobes but also inhibit the growth of hydrogen-consuming anaerobes. In addition, the changes in pH value, oxidation-reduction potential, VFAs and soluble COD during hydrogen fermentation were also discussed.     

Nondestructive determination of soluble solids content and pH in tomato juice using NIR transmittance spectroscopy

The potential of near-infrared (NIR) transmittance spectroscopy to nondestructively detect soluble solids content (SSC) and pH in tomato juices was investigated. A total of 200 tomato juice samples were used for NIR spectroscopy analysis at 800–2400 nm using an FT-NIR spectrometer. Multiplicative signal correction (MSC), and the first and second derivative were applied for pre-processing spectral data. The relationship between SSC, pH, and FT-NIR spectra of tomato juice were analyzed via partial least-squares (PLS) regression. PLS regression models were able to predict SSC and pH in tomato juices. The r _c, RMSEC, RMSEP, and RMSECV for SSC were 0.92, 0.0703°Brix, 0.150°Brix, and 0.138°Brix, respectively, whereas those values for pH were 0.90, 0.0333, 0.0316, and 0.0489, respectively. It is concluded that the combination of NIR transmittance spectroscopy and PLS methods can be used to provide a technique of convenient, versatile, and rapid analysis for SSC and pH in tomato juices.     

Influence of storage time on parameters of colour stability of beef

Direct measurements of the oxygen partial pressure profiles at the surface of the longissimus dorsi muscle of six bulls were obtained by means of a solid-state-probe after 1 min and 5 h exposure to air at 5°C. Changes in muscle colour were examined at the same time. The results show the profiles of oxygen partial pressure at the muscle surface after differing storage times (1, 3, 5, 7, 11 and 13 days at 5°C). Up to 5 days post mortem, increases in oxygen partial pressure with lengthening storage periods also led to higher percentages of oxymyoglobin, following exposure to air 1 min to 5 h. Further storage for up to 13 days decreased oxygenation, despite higher oxygen partial pressures. There was no evidence of rapid autoxidation to metmyoglobin during a 5-h period of exposure to air. Obvious connections between oxygenation and measurements of a-value were not found. The Lab-values increased dependent on the length of storage time.     

Bactericidal effect of sodium chlorate on Escherichia coli O157:H7 and Salmonella typhimurium DT104 in rumen contents in vitro

Escherichia coli O157:H7 and Salmonella Typhimurium DT104 are important foodborne pathogens affecting the beef and dairy industries and strategies are sought to rid these organisms from cattle at slaughter. Both pathogens possess respiratory nitrate reductase that also reduces chlorate to the lethal chlorite ion. Because most anaerobes lack respiratory nitrate reductase, we hypothesized that chlorate may selectively kill E. coli O157:H7 and Salmonella Typhimurium DT104 but not potentially beneficial anaerobes. In support of this hypothesis, we found that concentrations of E. coli O157:H7 and Salmonella Typhimurium DT104 were reduced from approximately 1,000,000 colony forming units (CFU) to below our level of detection (< or = 10 CFU) following in vitro incubation (24 h) in buffered ruminal contents (pH 6.8) containing 5 mM added chlorate. In contrast, chlorate had little effect on the most probable number (mean +/- SD) of total culturable anaerobes (ranging from 9.9 +/- 0.72 to 10.7 +/- 0.01 log10 cells/ml). Thus, chlorate was bactericidal to E. coli O157:H7 and Salmonella Typhimurium DT104 but not to potentially beneficial bacteria. The bactericidal effect of chlorate was concentration dependent (less at 1.25 mM) and markedly affected by pH (more bactericidal at pH 6.8 than pH 5.6).     

pH值及溶解氧对灵芝多糖深层液态发酵的影响与控制

探讨了 pH值及溶解氧 (DO)对灵芝多糖深层液态发酵的影响和控制措施。结果表明 ,灵芝胞内多糖的生成与菌丝体的生长呈偶联型 ,胞外多糖的形成与菌丝体生长呈部分偶联型。菌丝体生长及胞内多糖产生的最适 pH值为 5 4 ,胞外多糖产生的最适 pH值为 4 6。菌丝体生长最适溶氧和胞外多糖生成最适溶氧基本一致 ,在 80 0 %左右 ,溶氧超过这一水平 ,不利于胞外多糖的形成。据此设计出灵芝多糖发酵 pH和DO优化控制条件 ,在此优化条件下进行发酵 ,灵芝菌丝体生物量、胞内多糖量、胞外多糖量较未经优化控制的发酵分别提高 57%、51%、31% ,总灵芝多糖产量提高了 33%