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1.
In order to make full use of soybean stalk produced in large quantity annually in China, a process is proposed for production of lactic acid from soybean stalk hydrolysate with Lactobacillus sake and Lactobacillus casei. Experiments were conducted using the proposed process and experimental results indicate that the potential of 242 mg (g stalk) −1 fermentable sugar is released from hydrolysate through enzymatic saccharication with a saccharication of 51%. The main sugar released from pretreated soybean stalk through enzymatic hydrolysis was a mixture of glucose, xylose and cellobiose at a ratio of 3.9:1.7:1. Fermentation of soybean stalk hydrolysate by L. sake and L. casei yielded the lactic acid conversion of 48% and 56%, respectively, however, lactic acid conversion increased to 71% by co-inoculation of both strains. L. sake and L. casei were able to degrade glucose, but unable to completely assimilate xylose and cellobiose. The proposed process can be used to produce lactic acid from soybean stalk hydrolysate. 相似文献
2.
It is important to produce L(+)-lactic acid at the lowest cost possible for lactic acid to become a candidate monomer material for promising biodegradable polylactic acid. In an effort to develop a high-rate bioreactor that provides high productivity along with a high concentration of lactic acid, the performance of membrane cell-recycle bioreactor (MCRB) was investigated via experimental studies and simulation optimization. Due to greatly increased cell density, high lactic acid productivity, 21.6 g L(-1) h(-1), was obtained in the reactor. The lactic acid concentration, however, could not be increased higher than 83 g/L. When an additional continuous stirred tank reactor (CSTR) was attached next to the MCRB a higher lactic acid concentration of 87 g/L was produced at significant productivity expense. When the two MCRBs were connected in series, 92 g/L lactic acid could be produced with a productivity of 57 g L(-1) h(-1), the highest productivity among the reports of L(+)-lactic acid that obtained lactic acid concentration higher than 85 g/L using glucose substrate. Additionally, the investigation of lactic acid fermentation kinetics resulted in a successful model that represents the characteristics of lactic acid fermentation by Lactobacillus rhamnosus. The model was found to be applicable to most of the existing data with MCRBs and was in good agreement with Levenspiel's product-inhibition model, and the Luedeking-Piret equation for product-formation kinetics appeared to be effective in representing the fermentation kinetics. There was a distinctive difference in the production potential of cells (cell-density-related parameter in Luedeking-Piret equation) as lactic acid concentration increases over 55 g/L, and this finding led to a more precise estimation of bioreactor performance. 相似文献
3.
Lactobacillus intermedius B-3693 was selected as a good producer of mannitol from fructose after screening 72 bacterial strains. The bacterium produced mannitol, lactic acid, and acetic acid from fructose in pH-controlled batch fermentation. Typical yields of mannitol, lactic acid, and acetic acid from 250 g/L fructose were 0.70, 0.16, and 0.12 g, respectively per g of fructose. The fermentation time was greatly dependent on fructose concentration but the product yields were not dependent on fructose level. Fed-batch fermentation decreased the time of maximum mannitol production from fructose (300 g/L) from 136 to 92 h. One-third of fructose could be replaced with glucose, maltose, galactose, mannose, raffinose, or starch with glucoamylase (simultaneous saccharification and fermentation), and two-thirds of fructose could be replaced with sucrose. L. intermedius B-3693 did not co-utilize lactose, cellobiose, glycerol, or xylose with fructose. It produced lactic acid and ethanol but no acetic acid from glucose. The bacterium produced 21.3 +/- 0.6 g lactic acid, 10.5 +/- 0.3 g acetic acid, and 4.7 +/- 0.0 g ethanol per L of fermentation broth from dilute acid (15% solids, 0.5% H(2)SO(4), 121 degrees C, 1 h) pretreated enzyme (cellulase, beta-glucosidase) saccharified corn fiber hydrolyzate. 相似文献
4.
To facilitate metabolic analysis, batch fermentations of Lactobacillus rhamnosus were carried out in a new defined medium. Biomass at 10.5 g/l and lactic acid at 67 g/l with a YP/S of 0.84 were achieved. The maximum specific growth rate and the average productivity were 0.49/h and 2.48 g/l.h, respectively. These are comparable to those of this organism and related organisms in complex media. Preliminary amino acid studies were also conducted, highlighting the importance of serine, asparagine, glutamine and cysteine. Kinetic analysis revealed that lactic acid production was predominantly growth-associated with growth associated and non-growth associated lactic acid constants of 0.389 mol/g-cell and 0.0025 mol/g-cell.h, respectively. Finally a kinetic model has been included to describe the fermentation of L. rhamnosus. 相似文献
5.
Lactobacillus cellobiosus, isolated from city wastes, produced an extracellular alpha-amylase and produced lactic acid by direct fermentation of waste potato mash. Using a 5% (w/v) potato mash with 3% (w/v) CaCO to neutralise the lactic acid produced, 50% conversion of starch to lactic acid occurred in 48 h without any other media supplement. 相似文献
6.
Immobilization of Lactobacillus rhamnosus ATCC7469 in poly(vinyl alcohol)/calcium alginate (PVA/Ca-alginate) matrix using “freezing–thawing” technique for application in lactic acid (LA) fermentation was studied in this paper. PVA/Ca-alginate beads were made from sterile and non-sterile PVA and sodium alginate solutions. According to mechanical properties, the PVA/Ca-alginate beads expressed a strong elastic character. Obtained PVA/Ca-alginate beads were further applied in batch and repeated batch LA fermentations. Regarding cell viability, L. rhamnosus cells survived well rather sharp immobilization procedure and significant cell proliferation was observed in further fermentation studies achieving high cell viability (up to 10.7 log CFU g−1) in sterile beads. In batch LA fermentation, the immobilized biocatalyst was superior to free cell fermentation system (by 37.1%), while the highest LA yield and volumetric productivity of 97.6% and 0.8 g L−1 h−1, respectively, were attained in repeated batch fermentation. During seven consecutive batch fermentations, the biocatalyst showed high mechanical and operational stability reaching an overall productivity of 0.78 g L−1 h−1. This study suggested that the “freezing–thawing” technique can be successfully used for immobilization of L. rhamnosus in PVA/Ca-alginate matrix without loss of either viability or LA fermentation capability. 相似文献
7.
Lactobacillus delbrueckii mutant Uc-3 utilizes both cellobiose and cellotriose efficiently, converting it into L(+) lactic acid. The enzyme activities of cellobiose and cellotriose utilization were determined for cell extracts, whole cells, and disrupted cells. Aryl-beta-glucosidase activity was detected only for whole cells and disrupted cells, suggesting that these activities are cell bound. The mutant produced 90 g/liter of lactic acid from 100 g/liter of cellobiose with 2.25 g/liter/h productivity. 相似文献
8.
The role of functionalized alginate gels as immobilized matrices in production of l (+) lactic acid by Lactobacillus delbrueckii was studied. L. delbrueckii cells immobilized in functionalized alginate beads showed enhanced bead stability and selectivity towards production of optically
pure l (+) lactic acid in higher yields (1.74Yp/s) compared to natural alginate. Palmitoylated alginate beads revealed 99% enantiomeric
selectivity (ee) in production of l (+) lactic acid. Metabolite analysis during fermentation indicated low by-product (acetic acid, propionic acid and ethanol)
formation on repeated batch fermentation with functionalized immobilized microbial cells. The scanning electron microscopic
studies showed dense entrapped microbial cell biomass in modified immobilized beads compared to native alginate. Thus the
methodology has great importance in large-scale production of optically pure lactic acid. 相似文献
9.
Batch cultures of Lactobacillus rhamnosus were carried out at different pH values in order to study the limitation of growth and lactic acid production by the hydrogen
ion, non-dissociated lactic acid and internal lactate concentrations. The effect of pH between 5 and 6.8 was studied at non-limiting
concentrations of glucose; this is more significant for the lactic acid fermentation rate than for the maximum specific growth
rate, as shown by the incomplete substrate consumption at lower values of medium pH and by the constant maximum cell mass
obtained within the range of pH values studied. To check whether these results were a direct consequence of the different
concentrations of the non-dissociated form of lactic acid at different external pH values, specific growth rates and lactic
acid productions rates were calculated for each external pH value. The same specific growth rates were observed at the same
non-dissociated lactic acid concentrations only at pH values of 5 and 5.5. For higher values of pH (pH > 6) the specific growth
rate falls to zero as the non-dissociated lactic acid concentration decreases. This shows that generalisations made from studies
performed within very narrow ranges of pH are not valid and that the non-dissociated form of lactic acid is not the only inhibiting
species. The internal pH was measured experimentally for each external pH value in order to calculate the internal lactate
ion concentration. This form is described to be the inhibitory one. The results obtained confirmed that the specific growth
rate reached zero at approximately the same lactate concentration for all the pH values studied.
Received: 31 January 1997 / Received revision: 15 May 1997 / Accepted: 19 May 1997 相似文献
11.
There is increasing scientific and commercial interest in using beneficial microorganisms (i.e., probiotics) to enhance intestinal health. Of the numerous microbial strains examined, Lactobacillus rhamnosus GG has been most extensively studied. Daily intake of L. rhamnosus GG shortens the course of rotavirus infection by mechanisms that have not been fully elucidated. Comparative studies with germfree and conventional rats have shown that the microbial status of an animal influences the intestinal cell kinetics and morphology. The present study was undertaken to study whether establishment of L. rhamnosus GG as a mono-associate in germfree rats influences intestinal cell kinetics and morphology. L. rhamnosus GG was easily established in germfree rats. After 3 days of mono-association, the rate of mitoses in the upper part of the small intestine (jejunum 1) increased as much as 14 and 22% compared to the rates in germfree and conventional counterparts, respectively. The most striking alteration in morphology was an increase in the number of cells in the villi. We hypothesis that the compartmentalized effects of L. rhamnosus GG may represent a reparative event for the mucosa. 相似文献
12.
Summary The process of lactic acid fermentation of lactose to lactic acid by Lactobacillus rhamnosus ATCC 7469 has been studied. The following processes have been explored: growth kinetics, as well as lactose utilization,
production of lactic acid and further degradation of lactic acid. The immobilization experiments were conducted with microbial
cells entrapped in polyacrylamide gels. Gels with different ratios of the monomer (acrylamide) and the cross-linking agent
( N,N′-methylene-bis-acrylamide) have been tested. These were used in a repeat-batch process. The current processes inside and
outside the gel particles were subjects of examination. The evolution of the activity of immobilized cells with repeated use
showed that the particles served mainly as a donor of cells for the free culture. In all experiments a very high degree of
conversion, 85–90% was observed. After several runs however, the particles were exhausted for microbial cells. A kinetic model
of the process of lactic acid production was developed. This model allowed the evaluation of the effect of microbial growth
and diffusion limitations inside the gel particles on the process rate and the separate contribution of the free and immobilized
cells to the overall fermentation process upon multiple use. 相似文献
13.
Production of lactic acid from date juice by fermentation has been studied using Lactobacillus casei subsp. rhamnosus as the producer organism. The optimum substrate concentration, expressed in its glucose content, was 60 g l(-1). Various nitrogen sources were compared with yeast extract in terms of their efficiency for lactic acid production. None of these nitrogen sources gave lactic acid concentrations as high as that obtained with yeast extract. As yeast extract supplementation was not economically attractive, different proportions of (NH4)2SO4 and yeast extract were used. When the elemental nitrogen ratio of(NH4)2SO4 to yeast extract was 4:1, the substrate use and efficiency of lactic acid production were the same as in date juice supplemented with 20 g l(-1) yeast extract (0:5). 相似文献
14.
Ram horns are a waste material from the meat industry. The use of ram horn peptone (RHP) as a supplement for lactic acid production was investigated using Lactobacillus casei. For this purpose, first, RHP was produced. Ram horns were hydrolysed by treating with acids (3 M H 2SO 4 and 6 M HCl) and neutralizing the solutions to yield ram horn hydrolysate (RHH). The RHH was evaporated to yield RHP. The amounts of protein, nitrogen, ash, some minerals, total sugars, total lipids and amino acids of the RHP were determined and compared with a bacto-tryptone from casein. When the concentrations (1–6% w/v) of the RHP were used in bacterial growth medium as a supplement, 2% RHP (ram horn peptone medium) had a maximum influence on the production of lactic acid by L. casei. The content of lactic acid in the culture broth containing 2% RHP (43 g l –1) grown for 24 h was 30% higher than that of the control culture broth (33 g l –1) and 10% higher than that of 2% bacto-tryptone (39 g l –1). RHP was demonstrated to be a suitable supplement for production of lactic acid. This RHP may prove to be a valuable supplement in fermentation technology. 相似文献
15.
Lactobacillus delbrueckii subsp. delbrueckii KCTC 1047, grown in de Man, Rogosa and Sharpe (MRS) or soymilk media, completely hydrolyzed the isoflavone glucosides, genistin and daidzin at 50 g ml –1, into their respective aglycones, genistein and daidzein within 30 min. Other lactic acid bacteria did not produce -glucosidase, the enzyme responsible for the hydrolysis of isoflavone glucosides, when cultured in MRS medium. Glucoside-hydrolyzing activity was induced in some lactic acid bacteria when cultured in soymilk medium. These strains hydrolyzed 70–80% of genistin into genistein and 25–40% of daidzin into daidzein. 相似文献
16.
Colloidal liquid aphrons (CLAs) are surfactant-stabilized solvent droplets which have recently been explored for predispersed solvent extraction (PDSE). We have compared the equilibrium distribution of lactic acid with solvent alone and with CLAs. In spite of the short contact time in the PDSE process with CLAs, there was little difference in equilibrium distribution with solvent alone. The toxicity of extractants and diluents on Lactobacillus rhamnosus was measured for in situ extraction. Long chain alcohols such as 1-octanol and 1-decanol were less toxic among diluents. CLAs reduced the toxicity of solvents on Lactobacillus rhamnosus. 相似文献
17.
Arabic date is overproduced in Arabic countries such as Saudi Arabia and Iraq and is mostly composed of sugars (70–80 wt%). Here we developed a fed-batch fermentation process by using a kinetic model for the efficient production of lactic acid to a high concentration from Arabic date juice. First, a kinetic model of Lactobacillus rhamnosus grown on date juice in batch fermentation was constructed in EXCEL so that the estimation of parameters and simulation of the model can be easily performed. Then, several fed-batch fermentations were conducted by employing different feeding strategies including pulsed feeding, exponential feeding, and modified exponential feeding. Based on the results of fed-batch fermentations, the kinetic model for fed-batch fermentation was also developed. This new model was used to perform feed-forward controlled fed-batch fermentation, which resulted in the production of 171.79 g l ?1 of lactic acid with the productivity and yield of 1.58 and 0.87 g l ?1 h ?1, respectively. 相似文献
18.
The use of date juice as a substrate for lactic acid production was investigated. Various nitrogen sources were compared with yeast extract for efficient lactic acid production by Lactobacillus casei subsp. rhamnosus. Among different nitrogen sources added to date juice (yeast extract, ammonium sulfate, tryptic soy, urea, peptone, and casein hydrolysate), yeast extract was the most efficient. The effect of yeast extract could have been due to its B vitamin content. The addition of five B vitamins at less than 25 mg/l to date juice with any nitrogen source enhanced lactic acid production to some extent, except for date juice with yeast extract or urea or peptone. The most significant increase was obtained with ammonium sulfate. Half of the yeast extract content (10 g/l) in a supplemented date juice could be replaced by a mixture of B vitamins at less than 25 mg/l, and ammonium sulfate at 2.6 g/l with no significant decrease in lactic acid production. 相似文献
19.
Genome shuffling is a powerful strategy for rapid engineering of microbial strains for desirable industrial phenotypes. Here we applied the genome shuffling to improve the glucose tolerance of Lactobacillus rhamnosus ATCC 11443 while simultaneously enhancing the L-lactic acid production. The starting population was generated by ultraviolet irradiation and nitrosoguanidine mutagenesis and then subjected for the recursive protoplast fusion. The positive colonies from library created by fusing the inactivated protoplasts were more likely to be screened on plates containing different concentrations of high glucose and 2% CaCO(3). Characterization of all mutants and wild-type strain in the shake flask indicated the compatibility of two optimal phenotypes of glucose tolerance and lactic acid enhancement. The lactic acid production, cell growth and glucose consumption of the best performing strain from the second round genome shuffled populations were 71.4%, 44.9% and 62.2% higher than those of the wild type at the initial glucose concentration of 150 g/l in the 16l bioreactor. Furthermore, the higher lactic acid concentrations were obtained when the initial glucose concentrations increased to 160 and 200 g/l in batch fermentation. 相似文献
20.
In this work a strategy for obtaining free amino-acids concentrate from an organic fraction of municipal solid waste compost and its use as a nitrogen source for lactic acid production, a compound widely used in different industries, using L. fermentum ATCC 9338 and L. plantarum NCIMB 8826 strains is described. Enzymatic digestion is based on the combined action of endoprotease Alcalase 1.5 MG and exoprotease Flavourzyme 500 MG. The highest degree of hydrolysis obtained under the optimal conditions was 41%. The use of glucanase Viscozyme L prior to protein hydrolysis helped to reduce the viscosity of the solution and promote the action of proteases, increasing its hydrolysis degree by 76%. The hydrolysate contained all 21 amino-acids, making it ideal for lactic acid bacteria growth. During shake flask cultivations the culture media was complemented with glucose as carbon source. Finally, with the hydrolysate, a maximum lactic acid concentration of 9.0 ± 0.2 g·L −1 and 11.1 ± 0.1 g·L −1 for L. fermentum ATCC 9338 and L. plantarum NCIMB 8826 respectively was obtained after 27 h. The innovation of the approach lies in exploiting the overproduction of compost for the production of lactic acid. 相似文献
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