Development of culture media containing spent yeast cells of Debaryomyces hansenii and corn steep liquor for lactic acid production with Lactobacillus rhamnosus

To develop a cost-effective fermentation medium, biomass of Debaryomyces hansenii coming from xylitol production and corn steep liquor was evaluated for lactic acid production by Lactobacillus rhamnosus in glucose-containing media. Glucose consumption and lactic acid generation were followed using a variety of media made with different nutrient supplementation. Under selected conditions, media containing glucose, biomass of D. hansenii and corn steep liquor as unique components led to product yields similar to those obtained in a fully supplemented medium.     

Kinetic analysis and mathematical modeling of growth and lactic acid production of Lactobacillus casei var. rhamnosus in milk whey

Lactobacillus casei is a lactic acid bacterium (LAB) that colonizes diverse ecological niches and that has found broad commercial application. The aim of this study was to characterize the kinetics of biomass production, lactic acid production, and substrate consumption of Lactobacillus casei var. rhamnosus cultured in deproteinized milk whey. Batch culture experiments were performed in an instrumented, 2-L, stirred tank bioreactor using different inoculum concentrations (0.5 to 1.0 g/L) and lactose levels (35 to 70 g/L). The time series of experimental data corresponding to biomass growth, lactose consumption, and lactic acid formation were differentiated to calculate the corresponding kinetic rates. Strong exponentially dependent product inhibition effects were evident at low lactic acid concentrations, and lactic acid production rate was partially associated with biomass growth. A mathematical model is presented that reproduces the experimental lactose, biomass, and lactic acid concentration profiles.     

Recovery of lactic acid by repeated batch electrodialysis and lactic acid production using electrodialysis wastewater

Repeated batch electrodialysis for lactic acid recovery was investigated using lactic acid solution and fermentation broth. In both cases, lactate fluxes averaged more than 7.0 moles/m2.h, lactate recovery reached more than 99% for all the batch runs, and specific energy consumption per unit lactate transported was lower than 0.25 kWh/kg-lactate. When electrodialysis wastewater was used as a fermentation medium, supplemented with 100 g/l glucose, up to 92.4 g/l lactic acid was produced with a productivity of 0.67 g/l.h. In addition, when electrodialysis wastewater was supplemented with 150 g/l whole-corn flour hydrolyzate and 5 g/l corn steep liquor, 2.5-fold and 1.8-fold increases in lactic acid productivity and maximum cell growth, respectively, were achieved, as compared with lactic acid fermentation using electrodialysis wastewater supplemented with glucose only.     

拟干酪乳杆菌乳酸发酵培养基氮源优化

从发酵原料成本的角度出发,首先对发酵培养基中的碳氮比进行优化,将培养基中的碳氮比(质量比)提高为28.97;然后逐步将原始发酵培养基中的进口分析纯试剂替代为国产试剂及工业级试剂,并实现了工业级酵母粉FM802和蛋白胨FP101的完全替代。经过5 L发酵罐验证表明,原料替代后,成本降低为原来的1/3,而发酵时间仅增加1 h。     

利用L.casei及L.lactis发酵乳清渗透液生产高纯度L-乳酸

以乳清渗透液为底物,补充其他营养成分,分批发酵生产L-乳酸.通过对8种乳酸菌的筛选,确定最佳发酵乳酸菌组合为L. casei和L. lactis(11).初始乳糖质量浓度为96g/L时,乳酸生产效率最高且达到6.05g/(L·h).经过对发酵条件的优化,确立了最佳发酵条件25%氢氧化钾溶液作为中和剂,发酵液pH值为6.0,在37℃进行厌氧发酵(通入100%氮气).优化的发酵液组成初始乳糖200g/L,酵母提取物10g/L,K2HPO41 g/L,MgSO4·7H20 0.5g/L,MnSO4·H20 0.05g/L.最高乳酸产量为192g/L,L-乳酸纯度迭95%,乳糖利用率达96%.     

白酒生产中乳酸菌的分布及主要代谢产物

乳酸菌是发酵产乳酸的一类革兰氏阳性菌,是大曲中的主要微生物菌系,对大曲中酯的形成是有利的,但在有些香型白酒(如清香、浓香型白酒)酿造中要控制或降低乳酸菌的作用.该文介绍了白酒生产中乳酸菌的分布,乳酸菌所产主要代谢产物的代谢途径及其对白酒的影响.     

Modelling pH evolution and lactic acid production in the growth medium of a lactic acid bacterium: application to set a biological TTI

Time temperature integrators or indicators (TTIs) are effective tools making the continuous monitoring of the time temperature history of chilled products possible throughout the cold chain. Their correct setting is of critical importance to ensure food quality. The objective of this study was to develop a model to facilitate accurate settings of the CRYOLOG biological TTI, TRACEO. Experimental designs were used to investigate and model the effects of the temperature, the TTI inoculum size, pH, and water activity on its response time. The modelling process went through several steps addressing growth, acidification and inhibition phenomena in dynamic conditions. The model showed satisfactory results and validations in industrial conditions gave clear evidence that such a model is a valuable tool, not only to predict accurate response times of TRACEO, but also to propose precise settings to manufacture the appropriate TTI to trace a particular food according to a given time temperature scenario.     

Optimization of the associative growth of novel yoghurt cultures in the production of biomass, β-galactosidase and lactic acid using response surface methodology

The associative growth of Streptococcus thermophilus 95/2 (St 95/2) and Lactobacillus delbrueckii ssp. bulgaricus 77 (Lb 77) isolated from the Toros mountain region of Turkey was investigated with respect to lactic acid, biomass and β-galactosidase enzyme production using response surface methodology (RSM). The ratio (St 95/2:Lb 77) of the strains and media formulation had significant effect on all responses (p < 0.001). The predicted enzyme activity (2.14 U mL^?1), lactic acid (22.50 g L^?1) and biomass (7.11 g L^?1) production at optimum conditions were very close to the actual experimental values (2.14 U mL^?1, 22.94 g L^?1 and 7.86 g L^?1, respectively). The optimum conditions were to use these cultures in a ratio of 1.66:1.62 (St 95/2:Lb 77) in a medium containing whey (5%), corn steep liquor (4%), potassium phosphate (2%) and peptone (2%) at 43 °C for 8 h. The associative growth provided 6.4% and 39% more β-galactosidase activity and 8.73% and 44% more lactic acid compared with the results obtained using pure St 95/2 and Lb 77 strains, respectively.     

Investigation on the elimination of yeasty flavour in yeast extract by mixed culture of lactic acid bacteria and yeast

Yeast extract (YE) is a kind of umami additives used in fermented condiments, it also has special yeasty flavour (YF), which is not widely accepted by some consumers. In this paper, the technology of mixed microbial transformation was applied to eliminate or cover up YF during mixed fermentation. FG10, which is produced by Hubei Angel Yeast Co. Ltd, is a kind of YE that has the distinctive YF and has been applied to the market. It had good sensory evaluation after 6 h with Saccharomycopsis fibuligera and Lactococcus lactis. At 6 h, compared with single fermentation, the number of bacteria of L. lactis was enhanced by 34.28%, and the number of bacteria of S. fibuligera was reduced by 47.93%. The yeasty flavoured substances propionic acid and butyric acid were completely removed. The result of GC-MS showed that acetal, phenyl acetaldehyde, 2,4-dimethylbenzaldehyde, benzaldehyde, isoamyl alcohol, 5-methyl-2-furan methanol, phenylethanol were generated or increased. Furthermore, the amino acids of YE were significantly different after fermentation by different microorganisms (P < 0.05), The flavour compounds and amino acids in YE before and after fermentation had closely correlation (r = 0.94), the consumption of amino acids in mixed fermentation promoted the variety of corresponding flavour compounds, which boosted the formation of free YF YE. In addition, taste substances lactic acid generated 6.27 ± 0.115 g L⁻¹ and nucleotides improved 15.05%, which were beneficial to natural YF free seasoning with YE as raw material.     

Influence of casein hydrolysates on the growth and lactic acid production of Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus

The growth performance of Lactobacillus delbrueckii subsp. bulgaricus (L. bulgaricus) and Streptococcus thermophilus (S. thermophilus) was determined in the presence of casein hydrolysates produced by the action of five proteolytic enzymes (Alcalase, Flavorzyme, Neutrase, Papain and Trypsin) with various degrees of hydrolysis (DH). In addition, these five kinds of casein hydrolysates were fractionated by ultrafiltration and the influence of the amino acid composition of the peptides on the growth and lactic acid yield of yoghurt lactic acid bacteria (LAB) was studied. The results showed that the ultrafiltered fraction (<3000 Da) was the determinant stimulator in crude hydrolysates. Furthermore, the hydrophilic amino acid residua including His, Lys, Glu and Ser were beneficial for bacterial growth. Compared with control, the cell growth and lactic acid yield of yoghurt LAB were increased with the supplementation of the peptides fraction (<3000 Da) produced with papain by 65.1% and 49.6%, respectively.     

浓香型白酒发酵中乳酸含量动态变化与相关微生物研究

在浓香型白酒固体发酵中,乳酸含量变化趋势具有一定的规律性.从不同阶段分离的微生物中,鉴别、统计产乳酸以及利用乳酸牛长的微牛物种类和数量.结果表明,发酵前1周内,乳酸利用菌的数量和性能略占优势(达到108水平),使乳酸含量保持较低水平(2%～2.5%),1周以后,乳酸利用菌数量下降明显(106水平),与产乳酸菌数量相近,使乳酸含量维持在较高水平.研究结果表明,既能产乳酸,又能利用乳酸的菌株,对固态发酵的影响结果与其产乳酸能力呈正相关.     

Kinetics of growth and glucose transport in glucose-limited chemostat cultures of Saccharomyces cerevisiae CBS 8066

The glucose transport capacity of Saccharomyces cerevisiae CBS 8066 was studied in aerobic glucose-limited chemostat cultures. Two different transport systems were encountered with affinity constants of 1 and 20 mM, respectively. The capacity of these carriers (Vmax) was dependent on the dilution rate and the residual glucose concentration in the culture. From the residual glucose concentration in the fermenter and the kinetic constants of glucose transport, their in situ contribution to glucose consumption was determined. The sum of these calculated in situ transport rates correlated well with the observed rate of glucose consumption of the culture. The growth kinetics of S. cerevisiae CBS 8066 in glucose-limited cultures were rather peculiar. At low dilution rates, at which glucose was completely respired, the glucose concentration in the fermenter was constant at 110 microM, independent of the glucose concentration in the reservoir. At higher dilution rates, characterized by the occurrence of both respiration and alcoholic fermentation, the residual substrate concentration followed Monod kinetics. In this case, however, the overall affinity constant was dependent on the reservoir glucose concentration.     

Influence of sucrose,high fructose corn syrup and honey from different floral sources on growth and acid production by lactic acid bacteria and bifidobacteria

Sage, alfalfa and sourwood honey, which vary in their oligosaccharide contents, were compared with sucrose, high fructose corn syrup and inulin in their ability to support growth, activity and viability of lactic acid bacteria and bifidobacteria typically used in yoghurt manufacturing. Growth and the end products of fermentation (lactic and acetic acids) were determined. Growth and acid production by organisms studied in the presence of different sweeteners were dependent on the specific organism investigated; however, it was not influenced by sweetener type, oligosaccharide content or the floral source of the honeys. All the sweeteners studied supported the growth, activity and viability of the organisms studied.     

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.     

浓酱兼香型酒醅中乳酸菌的分离鉴定及布氏乳杆菌生长特性分析

采用平板分离法,从浓酱兼香型不同轮次酒醅中分离乳酸菌,并采用分子生物学技术进行鉴定,同时测定不同布氏乳杆菌（Lactobacillus buchneri）的生长特性。结果表明,共分离到30株乳酸菌,归属于3个属共5个种,其中布氏乳杆菌最多（21株）,占总分离菌株数的70%,是第三和第四轮出池酒醅的优势乳酸菌。所检测的19株布氏乳杆菌（L. buchneri）的最适生长温度为37 ℃,最适生长pH值大多在4.5左右,对乙醇的耐受能力在2%～10%之间。与植物乳杆菌（Lactobacillus plantarum）相比,所检测的6株布氏乳杆菌表现出了较强的发酵产柠檬酸和乙酸的能力,其平均柠檬酸产量为3.76 g/L,平均乙酸产量为4.22 g/L,分别是植物乳杆菌（L. plantarum）ZR1的11.13倍和1.80倍。     

Measurement of the concentrations of glucose and lactic acid in peritoneal dialysis solutions using near-infrared spectroscopy

Near-infrared spectroscopy (NIR), a nondestructive analytical technique, was employed for the simultaneous determination of the concentrations of glucose and lactic acid in peritoneal dialysis solutions. Solutions were placed in a near-infrared spectrophotometer and the absorbance at wavelengths between 400 and 2500 nm was measured at 2 nm intervals. To obtain calibration equations, multiple linear regression (MLR) was carried out on the NIR spectral data and on the glucose and lactic acid concentrations obtained by enzymatic methods using a calibration sample set. The value of the simple correlation coefficient (r) was 0.996 when using a wavelength of 2270 nm for glucose. The value of the multiple correlation coefficient (R) for lactic acid was 0.997 when using wavelengths of 1688 and 1268 nm. To validate the calibration equations obtained, glucose and lactic acid concentrations in a prediction sample set which was not used for calibration were calculated using the calibration equation and compared with the concentrations measured by the enzymatic method. Excellent agreement between the results of the enzymatic method and of NIR was observed for both constituents. Concentrations of glucose and lactic acid in the peritoneal dialysis solutions were analyzed simultaneously by NIR. The procedure for NIR was simple, and the operation time required to determine the concentrations was a few minutes. These results indicate that NIR may be a useful method for monitoring of the production of peritoneal dialysis solutions.