Study of starch fermentation at low pH by Lactobacillus fermentum Ogi E1 reveals uncoupling between growth and alpha-amylase production at pH 4.0

Lactobacillus fermentum Ogi E1 is an amylolytic heterofermentative lactic acid bacterium previously isolated from ogi, a Benin maize sourdough. In the present study, the effect of different pH between 3.5 and 6.0 on starch fermentation products and alpha-amylase production was investigated. Whereas a pH of 5.0 was optimum for specific growth rate and lactic acid production, growth was only slightly affected at suboptimal pH of 4.0 and 6.0. Over a pH range of 6.0 to 3.5, yields of product formation from substrate and of biomass relative to ATP were constant. These results showed that L. fermentum Ogi E1 was particularly acid tolerant, and well adapted to the acid conditions that develop during natural fermentation of cereal doughs. This acid tolerance may partly explain the dominance of L. fermentum in various traditional African sourdoughs. Surprisingly, alpha-amylase production, unlike growth, dropped dramatically when the strain was cultivated at pH 4.0 with starch. With maltose as substrate, the yield of alpha-amylase relative to biomass remained unchanged at pH 4.0 and 5.0, unlike that observed with starch. Based on the distribution of enzyme activity between extra- and intracellular fractions and fermentation kinetics, it appears that starch was first hydrolyzed into dextrins by alpha-amylase activity, and maltose was produced from dextrins by extracellular enzyme activity, transferred into the cell and then hydrolyzed into glucose by intracellular alpha-glucosidase.     

一株发酵乳杆菌(Lactobacillus fermentium)对柠檬酸的发酵特性研究

本文讨论了一株能高效转化利用高酸性水果(如青梅)中柠檬酸的发酵乳杆菌菌株的发酵特性。结果表明,该菌株能在以柠檬酸为主要碳源和能源的基础培养液中进行发酵生长,在转化利用柠檬酸的过程中仅仅产生少量的乙酸和乳酸,因此能将培养液中可滴定酸含量降低50%以上。菌株对乙醇具有较高的耐受性,当培养液中乙醇浓度达到9%(V/V)以上时,菌株的生长和柠檬酸代谢也就受到明显的抑制;菌株对亚硫酸盐非常敏感,培养液中仅仅添加0.5 m M的亚硫酸钠后,菌株的生长和柠檬酸代谢将会被完全抑制。培养液中蔗糖的添加能促进菌株的生长和柠檬酸代谢,但在柠檬酸存在的情况下,该菌株对蔗糖的转化利用较弱,因此,发酵期间培养液中糖的总含量并没有出现明显的下降。     

植物乳杆菌和发酵乳杆菌发酵对蓝莓花色苷的影响

选用植物乳杆菌（Lactobacillus plantarum）FM-LP-9和发酵乳杆菌（Lactobacillus fermentum）FM-LP-SR6分别对蓝莓花色苷进行发酵,考察发酵过程中菌落总数、pH值、色差、总黄酮含量、总糖含量、总花色苷含量、单体花色苷含量、有机酸含量等指标的变化规律。结果表明,经48 h发酵后,两种乳杆菌的菌落总数均能达到9.0 lg（CFU/mL）以上,发酵液的pH值降至3.6,总糖含量相较于发酵前分别降低了48.65%和58.97%,总黄酮含量分别增加至11.4、11.8 mg/L,总花色苷含量分别降低了48.63%和46.06%,色差值升高,颜色变暗。两株乳杆菌均能代谢花色苷和转化酚类物质,发酵过程中花色苷含量呈下降趋势,主成分分析得出两株乳杆菌发酵花色苷后的单体花色苷组分差异较大,主要来自飞燕草素-3-O-葡萄糖苷和矢车菊素-3-O-葡萄糖苷。此外,两株菌发酵后,发酵液中的乳酸、乙酸含量升高,草酸、苹果酸、柠檬酸含量降低。     

发酵乳杆菌适度发酵替代红肠生产中亚硝酸盐发色效果的研究

将发酵乳杆菌JCM1173适度发酵,在红肠生产中替代亚硝酸盐,以形成红肠的特征性腌肉红色,并和常规的生产作对照。通过紫外/可见光谱扫描发现,发酵乳杆菌JCM1173在发酵肉的过程中形成NO-Mb,而且在试验范围内,添加量越高,形成的NO-Mb浓度越大,当添加量为108个/g(肉)时,其NO-Mb含量接近60mg/kg亚硝酸盐腌制的肉。成品红肠的a值和感官评定也表现出相似的规律。这说明发酵乳杆菌JCM1173可以用于红肠生产中,代替亚硝酸盐发色。     

发酵乳杆菌CECT 5716产胞外多糖培养基成分优化及抗氧化活性研究

采用单因素和正交试验对发酵乳杆菌(Lactobacillus fermentium)CECT 5716产胞外多糖(EPS)的培养基成分进行优化,并通过评价胞外多糖对1,1-二苯基-2-三硝基苯肼(DPPH)自由基和2,2-联氮-二(3-乙基-苯并噻唑啉-6-磺酸)二铵盐(ABTS)自由基的清除活性以及其总抗氧化能力和Fe³⁺总还原力考察胞外多糖的抗氧化活性。结果表明,发酵乳杆菌CECT 5716产胞外多糖的最优培养基配方：麦芽糖2.0%、蔗糖1.0%、酵母膏2.5%、L-半胱氨酸盐酸盐0.2%、乙酸钠0.5%、磷酸氢二钾0.2%、硫酸镁0.02%、硫酸锰0.005%、柠檬酸氢二胺0.2%、吐温80 0.1%。在此条件下,EPS产量为(1 575±22.91)mg/L,是优化前的6.38倍。胞外多糖具有较好的抗氧化活性,并与其质量浓度成正比,当胞外多糖的质量浓度为8 mg/m L时,对DPPH自由基的清除率为(84.17±1.30)%、对ABTS自由基的清除率为(35.37±1.24)%,总抗氧化能力为0.31±0.01、Fe³⁺总还原力为0....     

Effect of prebiotic carbohydrates on the growth and tolerance of Lactobacillus

Resistance to gastrointestinal conditions is a requirement for bacteria to be considered probiotics. In this work, we tested the resistance of six different Lactobacillus strains and the effect of carbon source to four different gastrointestinal conditions: presence of α-amylase, pancreatin, bile extract and low pH. Novel galactooligosaccharides synthesized from lactulose (GOS-Lu) as well as commercial galactooligosaccharides synthesized from lactose (GOS-La) and lactulose were used as carbon sources and compared with glucose. In general, all strains grew in all carbon sources, although after 24 h of fermentation the population of all Lactobacillus strains was higher for both types of GOS than for glucose and lactulose. No differences were found among GOS-Lu and GOS-La. α-amylase and pancreatin resistance was retained at all times for all strains. However, a dependence on carbon source and Lactobacillus strain was observed for bile extract and low pH resistance. High hydrophobicity was found for all strains with GOS-Lu when compared with other carbon sources. However, concentrations of lactic and acetic acids were higher in glucose and lactulose than GOS-Lu and GOS-La. These results show that the resistance to gastrointestinal conditions and hydrophobicity is directly related with the carbon source and Lactobacillus strains. In this sense, the use of prebiotics as GOS and lactulose could be an excellent alternative to monosaccharides to support growth of probiotic Lactobacillus strains and improve their survival through the gastrointestinal tract.     

Statistical optimisation of the exopolysaccharide production by Lactobacillus fermentum Lf2 and analysis of its chemical composition

Lactobacillus fermentum Lf2 produces high amounts of exopolysaccharides (EPS) (~1 g/L) with demonstrated functional and technological roles when applied as a food ingredient in dairy matrices, properties that made these EPS interesting in comparison with other similar molecules from lactic acid bacteria (LAB). Those characteristics encouraged us to optimise the production. The EPS extract is composed of a high molecular mass β‐glucan and a medium molecular mass heteroglycan. In the present work, the optimal conditions that doubled the EPS yield using a semidefined medium (SDM, 0.63% yeast nitrogen base, 0.53% bacto casitone, 0.53% ammonium citrate, 6.25% sucrose, pH 6.5) were found by means of response surface methodology (RSM). The chemical characterisation indicated that under optimised conditions the synthesis of the heteroglycan was favoured compared with that of the β‐glucan.     

Fermentation of table cream by Lactobacillus plantarum strains: effect on fungal growth,aflatoxin M1 and ochratoxin A

Aflatoxin M1 (AFM₁) and ochratoxin A (OTA) are two main mycotoxins in milk and dairy products. In the present work, the ability of four Lactobacillus strains (L. plantarum PTCC 1058, L. plantarum LP3, L. plantarum AF1 and L. plantarum LU5) to remove AFM1 and OTA in fermented cream was studied during 24 h fermentation. The antifungal activity of the mentioned lactobacilli against the defined fungi (Aspergillus flavus PTCC 5004, Aspergillus parasiticus PTCC 5018, Aspergillus nidulans PTCC 5014, Aspergillus ochraceus PTCC 5060) was also evaluated. The results showed that the cell counts of all strains were increased by 64–70% during fermentation. All Lactobacillus strains decreased the amount of AFM₁ significantly (P ≤ 0.05) in the range of 26–52%, which the highest AFM₁-reducing effect was related to L. plantarum LU5 (from 0.5 to 0.24 μg kg⁻¹). The mean OTA removal by Lactobacillus strains in fermented cream also ranged from 32 to 58%. Amongst Lactobacillus strains, the cell-free culture supernatants of L. plantarum LU5 showed the highest (inhibition zone of 26.7 ± 1.2 mm) and L. plantarum LP3 and L. plantarum PTCC 1058 the lowest antifungal activities. The fermented creams contained Lactobacillus strains exhibited the highest and lowest antifungal activities against A. ochraceus and A. parasiticus, respectively. L. plantarum LU5, with the inhibition zone of 27.6 ± 0.9 mm, was the most effective fungal inhibitor, while L. plantarum PTCC 1058 had the lowest antifungal activity.     

Enumeration and growth of naturally occurring Listeria spp. in unpackaged ham

A total of 301 unpackaged retail ham samples were tested for the presence and number of Listeria spp. after 7 days at 5 degrees C to simulate domestic storage. Thirteen samples (4.3%) contained Listeria monocytogenes, with the highest count being 1.6 x 10(3)cfu g(-1). Thirteen samples contained other Listeria spp. Genotyping showed that only one L. monocytogenes isolate from the 14 tested was of a type previously identified in New Zealand human cases. Listeria-contaminated batches were incubated at 5 degrees C over approximately 3 weeks to assess the growth rate of natural contaminants. None contained L. monocytogenes, but growth occurred in one sample containing Listeria welshimeri and four containing Listeria innocua. Growth was usually slow at 0.002-0.004 log h(-1). In one sample, L. innocua grew at 0.02 log h(-1) although the maximum number reached was only 4.0-5.0 x 10(3)cfu g(-1). In five other samples little growth, if any, occurred. Growth of naturally occurring Listeria spp. at 5 degrees C was therefore generally slower than predicted by the Pathogen Modelling Programme (PMP) or did not occur.     

Lactobacillus Fermentum发酵降酸对三华李汁品质的影响

本文分析了三华李汁发酵乳杆菌发酵降酸期间乳酸菌活菌数、糖组分、有机酸、p H、可滴定酸、总酚、抗氧化活性、花色苷、色泽的变化规律。结果表明,在30℃的条件下,发酵乳杆菌缓慢生长,发酵6 d后,菌种数量趋于稳定;发酵期间,菌株对糖的利用较缓慢,仅利用少量的葡萄糖维持代谢生长,而对苹果酸的消耗较快。随着苹果酸的大量消耗以及少量乳酸的生成,三华李汁的p H值快速上升,可滴定酸含量迅速下降;发酵8 d后,菌种数量由初始的7.01 log CFU/m L增加到7.91 log CFU/m L,苹果酸被完全消耗,葡萄糖保留73.82%,果糖保留97.7%,p H值上升了0.38,可滴定含量下降了43.7%,总酚保留82.23%,抗氧化活性(ORAC值)升高了14.90%,花色苷保留50%以上,三华李汁的色泽变化不显著(p0.05)。因此,利用乳酸菌发酵三华李汁,不仅能够降低三华李汁酸度,而且很好地保留了三华李本身的营养成分。     

Kinetic analysis of growth and sugar consumption by Lactobacillus fermentum IMDO 130101 reveals adaptation to the acidic sourdough ecosystem

The effect of pH on growth and carbohydrate metabolism of L. fermentum IMDO 130101 was investigated. Pronounced acid tolerance occurred together with marked responses in sugar metabolism due to acid stress. In accordance with the environment from which this strain was isolated, glucose and fructose metabolism remained active at low pH. Fructose was quantitatively converted into mannitol under all conditions tested, yielding an energetic advantage to the strain. Modelling of growth, sugar consumption, lactic and acetic acid production, and mannitol production of L. fermentum IMDO 130101 allowed the estimation of its basic biokinetic parameters when growing under simulated sourdough conditions. The obtained kinetic data underline the competitiveness of the strain in an acidic environment.     

Influence of combinations of Lactobacillus lactis and potassium sorbate on growth of psychrotrophs in raw milk

Cells of Lactobacillus lactis from frozen concentrated cultures were added (1 X 10(8)/ml) to refrigerated raw milk to determine their effect on growth of psychrotrophs during storage of the milk at 5 or 7 degrees C. Some strains of Lactobacillus lactis were significantly inhibitory toward the psychrotrophs in refrigerated raw milk at both temperatures. Two selected strains of Lactobacillus lactis were added along with potassium sorbate (.1 and .2%) to refrigerated raw milk stored at 5 degrees C to determine their combined effect on growth of the psychrotrophs. The combinations of cells of lactobacilli and sorbate were more inhibitory than either lactobacilli or sorbate alone. The measurement of hydrogen peroxide produced by strains of Lactobacillus lactis indicated that the strains most antagonistic toward psychrotrophs also were the more active producers of hydrogen peroxide. Addition of sorbate had no apparent effect on hydrogen peroxide production by the cultures during refrigerated storage.     

Effect of physiological and production activities on the concentration of naturally occurring steroid hormones in raw milk

This study aimed to collect comprehensive experimental data and evaluate the effects of physiological and production activities on the concentration of naturally occurring steroid hormones in raw cow milk. The average levels of the hormones analysed (progesterone = 12 680 ng/kg and cortisol = 284 ng/kg) were comparable with data reported in the literature. Oestradiol, testosterone and methyltestosterone were not detected at their respective limits of quantification. Progesterone concentrations from individual cows have shown large variations ranging from 204 to 26 503 ng/kg, linked to the gestational status (pregnant/nonpregnant), lactation stages and gestational ages of the mammals. The average concentration of cortisol reaches a peak in the morning, decreases in the afternoon and reaches the lowest level at midnight. It is therefore evidenced that physiological and production activities have an effect on some hormonal levels in raw cow milk.     

产L-乳酸的嗜热乳酸杆菌(T-1)发酵动力学研究

本文对Lactobacillus thermophilus（T-1）的5L罐L-乳酸发酵过程进行了研究,并建立了菌体生长,底物消耗及产物生成动力学模型。经验证,模型的理论值和实验值拟和较好。所建动力学模型对反应器设计、工艺原理以及有效的控制发酵过程具有指导意义。     

Effect of sodium chloride on growth and bacteriocin production by Lactobacillus amylovorus DCE 471

A kinetic investigation of the effect of sodium chloride on cell growth of Lactobacillus amylovorus DCE 471 and amylovorin L471 production was carried out through in vitro experiments using a temperature and pH prevailing during sourdough fermentations. Sodium chloride interfered both with cell growth and bacteriocin production. Biomass formation and amylovorin L471 production decreased in the presence of increasing salt concentrations. Maximum bacteriocin activities were observed after the addition of 10 g l(-1) of NaCl, while the maximum specific growth rate reached an optimum at 5 g l(-1) of NaCl. High salt concentrations (20-40 g l(-1)) resulted in biphasic fermentation profiles. Based on these results, incorporation of 5-10 g l(-1) of sodium chloride in the water phase of type II sourdough preparations might be beneficial to enhance bacterial growth and amylovorin L471 production, and so contribute to the competitiveness of the strain in a sourdough environment.     

Aspergillus flavus growth in the presence of chemical preservatives and naturally occurring antimicrobial compounds

The combined effects of water activity ([a(w)] 0.99 or 0.95), pH (4.5 or 3.5) and antimicrobial agent (potassium sorbate, sodium benzoate, sodium bisulfite, carvacrol, citral, eugenol, thymol, or vanillin) concentration (0, 100, 200 up to 1800 ppm) on the growth of Aspergillus flavus were evaluated in potato dextrose agar (PDA). Mold spore germination time and radial growth rates (RGR) were significantly (p<0.05) affected by the variables. For equal antimicrobial concentration, reduction in pH or a(w) had important effects, lowering RGR and delaying germination time. Depending on a(w) and pH, increase in antimicrobial concentration slightly reduced RGR until a critical concentration where RGR was drastically reduced or mold growth was inhibited. Germination time increased as antimicrobial agent concentration increased and when a(w) and pH decreased. Important antimicrobial differences were observed, being, in general, the natural antimicrobials less pH-dependent than chemical preservatives. A. flavus exhibited higher sensitivity to thymol, eugenol, carvacrol, potassium sorbate, sodium bisulfite, and sodium benzoate (at pH 3.5) than to vanillin or citral.     

Effect of inulin on growth and bacteriocin production by Lactobacillus plantarum in stationary and shaken cultures

The prebiotic effect of inulin added to MRS medium on growth and bacteriocin production by L. plantarum ST16 Pa was investigated in stationary cultures in anaerobic jars with medium containing 0.025% sodium thioglycolate or in flasks shaken at 100 rpm. In the presence of 1% inulin in anaerobic stationary cultures, this strain produced lactic acid at a level that was 36.5% higher than in the absence of the polysaccharide. In shaken cultures without inulin, cell count was 54% higher than in the stationary ones. Under stationary conditions in anaerobic jars, the addition of inulin increased the maximum specific growth rate from 0.37 to 0.49 h^?1 and reduced the generation time from 1.85 h to 1.40 h. Consequently, the exponential phase was shortened from 12 to 9 h when the cells were grown in stationary cultures with the oxygen scavenger. Despite this effect of inulin on growth rate, stationary cultures without inulin displayed higher antimicrobial activity against Listeria monocytogenes L104 (3200 AU/mL) than cultures with inulin (1600 AU/mL); therefore, inulin behaved as a compound able to accelerate growth rather than to stimulate bacteriocin production. The results presented in this study are very promising, as L. monocytogenes is a well‐known foodborne pathogenic microorganism. Moreover, L. plantarum ST16 Pa has proven to be a potential producer of a natural food preservative at an industrial level.     

外源信号分子AI-2对发酵乳杆菌TG4-1-1和乳酸片球菌11-3产胞外多糖的影响

研究群体感应信号分子AI-2对发酵乳杆菌TG4-1-1和乳酸片球菌11-3胞外多糖产量的影响,探讨信号分子AI-2对乳酸菌分泌胞外多糖的调控机制。采用苯酚-硫酸法和哈维氏弧菌BB170生物发光法测定菌株不同培养时间胞外多糖产量和AI-2活性,筛选添加最佳浓度的外源信号分子AI-2,测定菌株的生长量、胞外多糖产量、AI-2活性,扫描电镜观察菌体形态及冷冻干燥后多糖形态。结果表明:发酵乳杆菌TG4-1-1和乳酸片球菌11-3均在10 h时AI-2活性最强,22 h时胞外多糖产量最高,分别达到(195.863±1.643)mg/L和(125.179±1.458)mg/L。100μmol/L外源AI-2为菌株TG4-1-1和11-3的最佳添加浓度,而该浓度对两株菌各阶段生长量均无显著影响(P>0.05),对菌株TG4-1-1在16～22 h和菌株11-3在13～22 h的胞外多糖产量有显著促进作用(P<0.05)。同时,显著增强试验菌株在10 h时AI-2的活性(P<0.05)。添加100μmol/L外源AI-2培养13 h后菌体表面光滑,形状规则,形态饱满,其对胞外多糖形态...     

Comparison of the performances of different fermentation strategies on cell growth and bacteriocin production by Lactobacillus curvatus CWBI‐B28

The dynamics of cell growth and bacteriocin production by Lactobacillus curvatus CWBI‐B28 in modified De Man/Rogosa/Sharp (mMRS) broth with various concentrations of glucose and complex nitrogen source (CNS; peptone, yeast extract and meat extract) was investigated in flask fermentations and in a laboratory fermentor using batch and fed‐batch cultivations. In fed‐batch fermentation the rate of feeding of the reactor with the substrates was either maintained constant (0.12 L h^?1) or varied exponentially as a function of time. The results showed that both cell growth and bacteriocin activity were influenced by changes in the concentrations of glucose and CNS. Optimal growth and bacteriocin activity were obtained in mMRS broth containing 40 g L^?1 glucose and 40 g L^?1 CNS (mMRS_40/40). A bacteriocin titre of 4266 AU mL^?1 and a cell count of 8.7 log colony‐forming units (cfu) mL^?1 were recorded when this medium was used for cultivation. In batch fermentation using the same medium, a higher cell count (9.5 log cfu mL^?1) and twice as much bacteriocin as in flask fermentation were produced. The highest bacteriocin titre (8533 AU mL^?1) was obtained with fed‐batch fermentation at an exponentially varying rate of feeding. Bacteriocin activity and cell dry mass did not always correlate. Copyright © 2007 Society of Chemical Industry     

发酵乳杆菌CQPC04减轻小鼠血栓形成和调节肠道菌群的效果

本研究通过给小鼠注射0.01 mL/(g mb·d)质量分数0.2%的角叉菜胶建立血栓形成模型,分析以0.2 mL/(g mb·d)不同浓度(1×10⁸ CFU/mL和1×10⁹ CFU/mL)发酵乳杆菌(Lactobacillus fermentum)CQPC04(以下简称LF-CQPC04)菌悬液干预10 d对小鼠凝血情况、氧化应激水平、炎症水平及肠道微生物组成的影响。分别采用生化试剂盒、苏木精-伊红染色切片观察、定量聚合酶链式反应分析小鼠血清和组织的相关指标,并通过高通量测序分析小鼠肠道微生物组成。结果表明,LF-CQPC04干预可以缩短血栓性小鼠的黑尾长度、凝血酶原时间、凝血酶时间,同时减少血液中纤维蛋白原质量浓度,延长血栓性小鼠的活化部分凝血活酶时间。LF-CQPC04干预还可降低血栓性小鼠血清中丙二醛、肿瘤坏死因子(tumor necrosis factor,TNF)-α、白细胞介素(interleukin,IL)-6、核因子(nuclear factor,NF)-κB和IL-1β的水平,并提高超氧化物歧化酶和过氧化氢酶(cata...