嗜热链球菌促生长物质研究及增殖培养基优化筛选

研究了在MRS培养基中添加不同营养物质对嗜热链球菌生长的影响,进一步采用正交试验优化筛选了嗜热链球菌的增殖培养基。结果表明:在MRS培养基中添加玉米浆、番茄汁、啤酒液、乳糖可显著促进试验菌株的细胞生长(P<0.01),而添加蛋白胨、酵母浸膏、CaCl2对细胞生长无显著影响(P>0.01);利用L934正交试验筛选出增殖培养基的最佳配比为:在MRS培养基中添加0.3%玉米浆、7.5%番茄汁、5.0%啤酒液、1.0%乳糖;试验菌株在增殖培养基中经37℃培养24h,活菌数可达4.69×109cfu/ml,较对照MRS培养基的活菌数提高40.78倍。     

PB试验优化德氏乳杆菌增殖培养基的研究

试验对一株来源于传统酸奶的优良德氏乳杆菌（Lactobacillus delbrueckii）ATx生长所需的增殖因子进行了研究。在MRS培养基的基础上,测定了菌株ATx的生长曲线,并选取谷氨酸钠、磷酸吡哆醛、抗坏血酸、啤酒、乳糖、胡萝卜汁、番茄汁、pH为增殖因子。采用单因素试验确定每个因子的最优水平,Plackett-Burman试验考察各因子对菌株ATx细胞增殖的影响,通过最陡爬坡与中心组合试验对增殖因子进行优化。结果表明,谷氨酸钠、啤酒以及pH对菌株ATx的增殖具有显著影响（P＜0.05）,当MRS培养基中添加谷氨酸钠21.5 g/L、啤酒26.8 mL/L、初始pH值为6.4时,德氏乳杆菌ATx的活菌数最大为（7.56±0.23）×109 CFU/mL,为高活性发酵剂的制备提供了理论参考。     

嗜热链球菌和保加利亚乳杆菌的增埴培养基的研制

嗜热链球菌 (S.t)和保加利亚乳杆菌 (L.b)在经典培养基中的生长情况结果显示 :S.t和 L .b在含有乳成分(例如 :乳清和酪蛋白水解物 )和天然促生长物质 (例如 :蕃茄汁 )生长相对较好 ;用不同浓度的乳、乳清及水解组分配合做为增殖培养基的基质 ,结果表明 :4%的脱脂乳和 5%的酶解乳清以 1∶ 1比例混合获得了较好的增菌效果 (使 S.t和 L .b均达到 1 0 8cfu/ml) ;根据在此基础上进行的增殖因子单因素试验结果 ,可以将增殖因子分为两类 ,一类是以酵母粉、蕃茄汁为代表的天然物质 ,另一类是以乳糖、缬氨酸为代表的化合物。     

培养条件对金黄色葡萄球菌-大肠杆菌混合生物被膜的影响

以常见食源性致病菌金黄色葡萄球菌和大肠杆菌为研究对象,采用微孔板法对混合生物被膜形成过程中的不同影响因素进行了研究。结果表明：在25 ℃或30 ℃条件下,采用质量分数0.8%的胰酶大豆肉汤（TSB）或0.8%的脑心浸出液（BHI）培养基培养时,生物被膜形成量较高;添加适量的葡萄糖、乳糖、麦芽糖和蔗糖可提高混合生物被膜形成能力;培养基中NaCl质量分数＞8%时,混合生物被膜的生长明显受到抑制。     

保加利亚乳杆菌番茄复合汁增菌培养基的优选研究

研究了在番茄汁基础培养基中添加不同营养物质对保加利亚乳杆菌生长的影响,进一步采用正交试验优化筛选了保加利亚乳杆菌L.b-S1的增殖培养基。结果表明,在番茄汁基础培养基中添加胰蛋白胨、酵母膏、碳酸钙可显著促进试验菌株的细胞生长(P<0.01);利用L933正交试验筛选出增殖培养基的最佳配比为:在番茄汁基础培养基中添加0.5%酵母膏、1.0%胰蛋白胨、0.3%碳酸钙;试验菌株在增殖培养基中经37℃培养18h,活菌数可达为2.25×1010mL-1,较液体MRS培养基的活菌数(4.98×108mL-1)提高了45.18倍,成本较液体MRS培养基降低1500元/t。为工业化大规模培养乳酸菌并研制开发直投式酸奶发酵剂提供了经济廉价的增菌培养基。     

干酪乳杆菌纯种发酵水苏糖合生元酸奶的菌种筛选与工艺

针对目前我国合生元功能性乳制品研发水平低,大多采用益生菌与传统酸奶菌混种发酵的现状,以分离自天然发酵食品、保健品和微生物制剂等的18株新型益生菌和3种商品化发酵剂中所含益生菌为试验菌株,以传统酸奶发酵菌株保加利亚乳杆菌和嗜热链球菌为对照菌株,研究菌株发酵牛乳的凝乳时间、产酸能力、感官品质,分析菌株利用水苏糖的增殖效果,筛选能利用水苏糖作为益生元生产合生元酸奶的益生菌菌株;测定了菌株在纯牛乳基础培养基中的生长曲线;研究了益生元增殖培养基中水苏糖的最适添加量;优化了水苏糖合生元酸奶产品的发酵工艺条件;检测了0 d和贮藏21 d合生元酸奶产品的质量。结果表明：新型益生菌干酪乳杆菌07-211具有发酵牛乳的能力,可利用水苏糖进行显著增殖,活菌数由3.19×108 CFU/mL增至2.05×109 CFU/mL;益生元增殖培养基中水苏糖的最适添加量为0.8%;干酪乳杆菌07-211纯种发酵水苏糖合生元酸奶的最佳工艺条件是：接种量3%,蔗糖添加量4%,发酵温度42 ℃,合生元酸奶凝乳时间4.15 h,pH 4.65,滴定酸度64.27 °T,活菌数3.96×109 CFU/mL,感官品评得分8.78分（10分制）。其中,0 d和贮藏21 d的合生元酸奶的质量均优于国标。本研究结果为工业化生产干酪乳杆菌纯种发酵水苏糖合生元酸奶产品提供理论依据,也为其它功能性合生元乳制品的研发提供借鉴。     

两株低温乳酸菌增殖培养基的优化

10℃条件下,以两株源于四川泡菜的耐低温乳酸菌3m-1(Lactobacillus plantarum)和8m-9(Leuconostoc mesenteroides)为研究对象,在白菜汁基础培养基中,研究添加不同氮源、碳源及缓冲剂对其生长的影响,并通过正交实验对增殖因子进行优化,确定了菌株3m-1和8m-9增殖的改良白菜汁培养基配方分别为:白菜汁基础培养基中添加蛋白胨1.0%、牛肉膏0.5%、乳糖1.0%、葡萄糖1.5%、磷酸氢二钾0.2%;白菜汁基础培养基中添加蛋白胨1.5%、牛肉膏1.0%、乳糖0.5%、葡萄糖1.5%、磷酸氢二钾0.2%。10℃条件下,菌株3m-1和8m-9在相应改良白菜汁培养基中培养72h,活菌数分别为6.05×109cfu/mL和7.35×109cfu/mL,较白菜汁基础培养基提高了6.1倍和10.4倍,而与MRS培养基培养相比,活菌数相近,研究结果为制备低温乳酸菌发酵剂具有指导意义,同时也为低温发酵泡菜的生产奠定了基础。     

嗜酸乳杆菌L101发酵增殖因子的研究

为促进嗜酸乳杆菌L101的生长,本研究以MRS为基础培养基,选取添加6种增殖因子(番茄汁、胡萝卜汁、平菇汁、黄豆芽汁、啤酒和低聚异麦芽糖),单因素试验比较了各因子增殖作用,正交试验研究选取促进活菌数提高的最佳增殖因子组合.试验结果表明:黄豆芽汁在各单因子中增殖效果最佳,当其在MRS培养基中添加浓度为10%(V/V),菌体在38℃下培养14 h时,活菌数可达4.034×109℃FU/ml;经正交试验所得最佳复合增殖因子组合为:黄豆芽汁5%(V/V)、平菇汁1O%(V/V)、番茄汁10%(V/V)和低聚异麦芽糖(10g/L).嗜酸乳杆菌L101在添加了该增殖因子组合的MRS培养基内培养14 h时,活菌数可达5.25×1O10CFU/ml.本研究为进一步提高嗜酸乳杆菌L101活菌数提供了必要的工艺参数.     

香肠乳杆菌增殖培养基及培养条件的优化研究

对香肠乳杆菌的增殖培养基及培养条件进行优化研究.根据乳酸菌生长增殖的营养物质需求,对其增殖培养基成分中的氮源、碳源、生长因子及缓冲盐进行选择,通过正交实验对各成分之间的配比进行了优化,确定了增殖培养基的最佳组成.采用单因素实验对发酵菌株的培养条件进行研究,确定培养温度、培养方式、培养基初始pH等.同时根据乳酸菌发酵变化曲线,确定发酵16～18h为发酵最佳收获期.     

优化两歧双歧杆菌培养基的增菌研究

针对两歧双歧杆菌的营养需要,采用正交实验设计优化增殖培养基。结果表明,酵母膏是短双歧杆菌的显著影响因素。最佳的优化培养基配比是:酵母膏0.9%,胰蛋白胨0.3%,大豆蛋白胨0.3%,葡萄糖2.0%,双歧因子0.8%,生长因子10%(均为质量分数)。用经优化的增殖培养基配方测定两歧双歧杆菌的生长曲线及其pH值的变化,确定该菌增殖培养的最适终止时间约为18h,此时平板菌落计数的菌数可高达2.1×1010mL-1。     

肉制品发酵剂的筛选与发酵特性的研究

以MRS培养基为基础培养基,从自然发酵香肠和自制腌肉中分离、筛选出三株乳酸菌(F1、F2、F3),对其生化特性、发酵特性、生长状况、产酸能力、致死温度及菌株间的拮抗性进行研究,结果表明:3株乳酸菌均符合肉制品发酵剂的要求,可以作为肉制品发酵剂;菌株F1和F3,F2和F3可以作为肉制品的混合发酵剂.     

Effects of mixed starter composition on nisin Z production by lactococcus lactis subsp. lactis biovar. diacetylactis UL 719 during production and ripening of Gouda cheese

A starter culture system that produced both acid and nisin at acceptable rates in milk for manufacture of Gouda cheese was developed using nisin Z-producing L. lactis subsp. lactis biovar. diacetylactis UL 719 (UL 719) and a commercial Flora Danica (FD) starter culture. Different compositions of mixed cultures (0, 0.2, 0.4, 0.6 or 0.8% UL 719 with 1.4% FD) were tested for acidification and nisin Z production in milk after 12 h incubation at 30 degrees C. The 0.6/1.4% combination, selected as the optimal mixture of starter cultures, acidified milk to a suitable pH and produced nisin Z at a high concentration of 512 IU/ml. With this optimal combination, FD numbers of citrate-fermenting and non-fermenting bacteria did not change compared with the control (1.4% FD). However, with 0.8% of L. lactis strain UL 719 and 1.4% of the FD starter culture, the numbers of citrate-fermenting and non-fermenting bacteria in fermented milk decreased compared with those obtained when milk was inoculated with 0.2, 0.4 or 0.6% of UL 719 added to 1.4% FD or control cultures (1.4% FD). Mixed starter culture ratios 0.6/1.4%, 0.4/1.4% and 0.5/1.4% (UL 719/FD) were used to manufacture nisin Z containing Gouda cheese which was ripened up to 45 weeks. The composition of control cheeses made with 1.4% FD, and nisin Z-containing Gouda cheeses were similar with respect to percent moisture, fat, salt and protein. During the ripening period, the cell counts observed were approximately two logs higher in cheese made with the 0.6/1.4% mixed starter culture than in control cheese. In experimental cheese produced with 0.6/1.4% (UL 719/FD) mixed starter culture, nisin activity increased from 256 IU/g at the end of manufacture to a maximum of 512 IU/g after 6 weeks of ripening; the levels then decreased to 128 and 32 IU/g after 27 and 45 weeks of ripening, respectively. In contrast, nisin Z was not detected in experimental cheeses made with 0.4/1.4% or 0.5/1.4% (UL 719/FD) mixed starters. Using an affinity purified anti-nisin polyclonal antibody, anti-rabbit gold-conjugate and transmission electron microscopy, nisin Z was found to be localized in the cheese matrix, in fat globules, in the casein phase and concentrated at the fat-casein interface. After 27 weeks of ripening, nisin Z was detected preferentially in the fat globules of the experimental cheese.     

THE MANUFACTURE AND USE OF STARTERS FOR THE DAIRY INDUSTRY: CHARACTERISTICS AND USE OF STARTER CULTURES IN THE MANUFACTURE OF HARD PRESSED CHEESE

The paper considers the classification, composition and growth properties of starter cultures and the significance of bacteriophage and inhibitor effects. The requirements for starter culture are examined and tables given summarizing the features of growth and acid production in milk. The importance of flavour characteristics and curd maturation is discussed, the effects of bacteriophage on cheesemaking studied, and the inhibitory substances present in milk analysed. The use of starter cultures and the selection of the most effective type - single, multiple or mixed strain - used in the production of hard cheese is assessed.     

Comparison of Genetic and Enological Characteristics of New and Existing S. cerevisiae Strains for Chardonnay Wine Fermentations

Wine makers are currently looking for ways to enhance the flavor and develop complexity in their wines by applying new enological tools, utilizing novel yeasts or mixed strain cultures. This research characterized the genetic fingerprints and killer phenotypes of two Burgundian yeast isolates (C2, C6). Chardonnay must was fermented, and the Burgundian yeast strains were assessed for their enological characteristics (ethanol, acetic acid, glycerol and sulfur dioxide production, foam formation, ethanol tolerance) in individual and mixed cultures and compared to six commercial wine strains. Their unique genetic fingerprints and killer positive phenotypes confirmed that the Burgundian strains would predominate in individual culture or would be able to grow simultaneously in mixed culture. Analyses of variance and principal component analysis were used to compare the enological characteristics of the individual and mixed strains. The individual and mixed strain fermentations of C2 and C6, were more similar to one another compared to the commercial strains, yet enologically equivalent. As such, the novel Burgundian yeast strains offer wine makers a new tool for customizing the characteristics and enhancing complexity of the wines, while ensuring that their enological characteristics are consistent with commercial requirements.     

Enhancement of styrene removal efficiency in biofilter by mixed cultures of Pseudomonas sp. SR-5

The styrene-degrading bacterium Pseudomonas sp. SR-5 exhibited a high styrene removability in a biofilter. However, the styrene removal efficiency (RE) of SR-5 decreased with time. We carried out styrene gas removal in a biofilter inoculated with mixed cultures of SR-5 and other microorganisms to determine the possibility of obtaining an enhanced RE for a long period. The following three inocula were carried out: (i) styrene-degrading bacteria, strains 1 and 3, (ii) a benzoic acid-degrading bacterium Raoultella sp. A, and (iii) wastewater from a chemical company dealing with styrene. These biofilters with mixed SR-5 showed an enhanced RE compared with those with a single culture of SR-5. The complete styrene elimination capacities for ensuring 100% styrene removal in those mixed cultures were 151, 108 and 124 g/m(3)/h, compared with a single culture of SR-5.     

假丝酵母ZD-3与黑曲霉ZD-8复合固体发酵对棉籽饼脱毒及营养价值的影响研究

研究目的为研究热带假丝酵母ZD-3与黑曲霉ZD-8复合固体发酵对棉籽饼粕脱毒效果、蛋白质营养价值及显微形态结构等的影响。利用热带假丝酵母ZD-3和黑曲霉ZD-8对棉籽饼进行单菌及复合固体发酵，然后测定发酵底物中游离棉酚（FG）、氨基酸含量，体外法测定饲料蛋白质氨基酸消失率，用环境扫描电镜拍摄底物发酵后的显微形态结构变化等。试验结果：复合发酵可极显著（P〈0．01）地降低棉籽饼底物游离棉酚含量，脱毒率为91．64％；棉籽饼底物粗蛋白、总氨基酸、必需氨基酸含量分别提高27．83％、18．15％、19、18％；提高粗蛋白、总氨基酸及必需氨基酸体外消化率分别为20．90％、26．16％、24．47％，赖氨酸和蛋氨酸分别增加20．24％、66．29％。环境扫描电镜图片表明，复合发酵处理棉籽饼底物后，黑曲霉形态结构发生变化，其菌丝变细，未观察到抱子头，只见光秃秃的顶囊。酵母菌形态未发现有明显变化。试验结果表明，复合发酵效果明显优于单菌发酵棉籽饼底物的效果，不但达到棉酚脱毒的目的，而且发酵饲料营养价值显著提高。复合发酵时，热带假丝酵母ZD-3对黑曲霉ZD-8的形态变化有显著影响。     

DETERMINATION OF pH CHANGE KINETICS DURING DIFFERENT STAGES OF KASHAR CHEESE MANUFACTURING FROM RAW AND PASTEURIZED MILK WITH ADDITION OF THERMOPHILIC, MESOPHILIC AND MIXED THERMOPHILIC CULTURE

The pH change kinetics during Kashar cheese production from raw and pasteurized milk with addition of thermophilic, mesophilic and mixed thermophilic-mesophilic lactic acid bacteria were evaluated. The kinetics of pH change were determined during milk ripening, cooking/holding and pressing/fermentation phases of Kashar cheese. The pH decreased logarithmically, nonlinearly, with time in the milk ripening period, and reduced linearly with time in the cooking/holding and pressing/fermentation stages. Pasteurization of milk retarded the rate of change in pH during the three periods. The highest rate of pH change was determined in the addition of thermophilic culture, followed by mixed thermophilic-mesophilic and then mesophilic ones during milk ripening. The pH change characteristics of cheese made with thermophilic starter were similar to the cheese made with mixed thermophilic-mesophilic culture, but different from mesophilic lactic acid bacteria during cooking/holding and pressing/fermentation stages.

PRACTICAL APPLICATIONS

One of the important factors in the control of cheese quality is the extent of acid production in the vat. Acid development at a desired rate is important during cheese making. The progress of acidification is monitored by pH change in the industrial Kashar cheese production. Three main stages have been recognized with respect to pH change: milk ripening, cooking/holding and pressing/fermentation. This study evaluated and compared the pH change kinetics during various stages of Kashar cheese making using raw, pasteurized milk with the addition of thermophilic, mesophilic and mixed thermophilic culture. This work may help in the comparison of raw and pasteurized milk, and in the selection of appropriate starter culture for Kashar cheese production.     

促进混合培养的保加利亚杆菌和嗜热链球菌生长的物质研究

通过在不同乳酸菌基础培养基中添加营养物质的研究,发现啤酒,番茄汁及ＣａＣｌ２均对混合培养的保加利亚杆菌和嗜热链球菌生长有一定影响。实验结果表明,２．５％啤酒可以促进两菌在全脂牛乳中生长及嗜热链球菌在乳清培养基中生长,５％番茄汁可以促进两菌在服清培养基中生长。ＣａＣｌ对两菌在ＢＬＣ培养液中有一定促进生长作用。     

EFFECTS OF TRISODIUM PHOSPHATE ON POPULATIONS OF SALMONELLA TYPHIMURIUM AND SALMONELLA ENTERITIDIS IN VITRO

This study determined the bactericidal activity of different concentrations of trisodium phosphate (TSP) against Salmonella typhimurium and Salmonella enteritidis in vitro. One milliliter of each TSP solution (0.5, 1, 1.5 and 2% w/v) was mixed with 1 mL of each bacterial culture and left to stand at room temperature (18  ±  1C) for 0, 15, 30, 45, 60 or 90 min before enumeration of the surviving pathogens.
The effects of 1.5 and 2% TSP were apparent on both bacterial species from 0 min and bacterial counts reached undetectable ( < 1.0  ×  10¹ cfu/mL) levels immediately. The 1% TSP solution effected close to 4.20–5.72 log reduction after 15 min. However, the reduction effect of 0.5% TSP was a function of treatment time, and some culturable bacteria remained even after 90 min of treatment. These results suggest that the bactericidal effect of TSP solution on these pathogens depends on its concentration and on the duration of treatment.

PRACTICAL APPLICATIONS

Poultry has been identified as one of the most important reservoirs of Salmonella typhimurium and Salmonella enteritidis in food chain. Efforts to eliminate or reduce Salmonella spp. and other pathogens attached to poultry carcasses during processing have been made for many years. In 1992, the U.S. Department of Agriculture approved the use of trisodium phosphate (TSP) as a processing aid to reduce Salmonella spp. on raw poultry carcasses. The aim of the present study was to determine the bactericidal effects of different concentrations of TSP on pure cultures of these pathogens in vitro .     

GENETIC ANALYSIS OF CRYOPHILIC AND MESOPHILIC WINE YEASTS

Ascospore genetic analysis, predominantly tetrad analysis, was performed upon 4 cryophilic and one mesophilic wine yeasts. Four strains appear to be homothallic; one may be heterothallic and polyploid. No segregation for the cryophilic character was obtained in 2 strains amenable to tetrad analysis. Overall, around 9% of ascospore cultures produced faster fermentations in laboratory-scale tests. Pilot-scale and industrial-scale trials gave promising results for the commercial use of 2 spore culture strains and one hybrid strain in the production of fruit wines.