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1.
The kinetics of nisin production was studied in batch cultures using a construct of Lactococcuslactis subsp. lactis C2SmPrt−, containing a transposon (TnNip) that encodes nisin production. The introduction of TnNip into C2SmPrt−significantly lowered the specific growth rate and the maximum A
620 reached was reduced from 15.2 to 11.0. The effect of nisin concentration and nutrient depletion on nisin production of the
construct, C2SmPrt−(TnNip), was examined. Nisin production was found to be inhibited by high concentrations of nisin, when grown in excess nutrient,
even though growth of the culture continued because nutrient limitation was not operating. However, in low nutrient concentrations
nisin production was limited by nutrient depletion. The specific growth rate of C2SmPrt−(TnNip) was altered, by using different nutrient concentrations and different sugars, in order to examine the relationship between
nisin production and growth. Nisin production was shown to be growth-associated for most of growth, but near the end of growth,
when the specific growth rate was 0.05 h−1 or less, the production ceased.
Received: 20 March 1997 / Received revision: 10 June 1997 / Accepted: 14 June 1997 相似文献
2.
C. Abate D. Callieri Emilio Rodríguez Oscar Garro 《Applied microbiology and biotechnology》1996,45(5):580-583
Pure and mixed cultures of Zymomonas mobilis and Saccharomyces sp. were tested for the production of ethanol using sucrose as the carbon source. Both strains, isolated from spontaneously
fermenting sugar-cane juice, are flocculent and alcohol-tolerant. The best results were obtained using a mixed culture, with
a yield of 0.5 g ethanol/g sugar consumed and a volumetric productivity of 1.5 g ethanol l-1 h-1. No levan was produced even if a sucrose-based medium was used.
Received: 20 April 1995/Received revision: 26 July 1995/Accepted: 13 September 1995 相似文献
3.
A continuous bioreactor packed with a fibrous matrix was set up. Cells of Pediococcus acidilactici PO2 were inoculated and MRS broth was fed gradually until cell growth and immobilization were achieved. Kinetics of fermentation
and production of bacteriocin were investigated at dilution rates ranging from 0.63 day-1 to 1.58 day-1 and at pH values that varied between 4.0 and 5.5. A maximum bacteriocin activity of 6400 AU/ml was detected when the medium
was fermented at dilution rates of at least 1.19 day-1 and the pH controlled at 4.5. The maximum bacteriocin productivity was 1.0×107 AUl-1 day-1 at a dilution rate of 1.58 day-1 and pH 4.5. At this high dilution rate, 1.21 g cells/l medium was produced, 95.9% of the glucose in MRS broth was utilized,
and 15.1 g lactic acid/l accumulated in the bioreactor effluent. The bioreactor was operated continuously for 3 months without
encountering any clogging, degeneration, or contamination problems, indicating good long-term stability of the bioreactor
for bacteriocin production. About 94% of the cells in the bioreactor were immobilized, and the remainder were suspended in
the medium. According to scanning electron microscopic observations, cell immobilization in the fibrous matrix was attained
by natural attachment to fiber surfaces and entrapment in the void volume within the fibrous matrix. In conclusion, conditions
for the optimum continuous production of pediocin were defined; this may facilitate the development of large-scale industrial
processes for production of this bacteriocin.
Received: 25 September 1995/Received revision: 30 November 1995/Accepted: January 1996 相似文献
4.
Octavio Carvajal-Zarrabal Cirilo Nolasco-Hipólito Kopli B. Bujang Ayaaki Ishizaki 《Journal of industrial microbiology & biotechnology》2009,36(3):409-415
A membrane bioreactor for production of nisin Z was constructed using Lactococcus lactis IO-1 in continuous culture using hydrolyzed sago starch as carbon source. A strategy used to enhance the productivity of
nisin Z was to maintain the cells in a continuous growth at high cell concentration. This resulted in a volumetric productivity
of nisin Z, as 50,000 IU l−1 h−1 using a cell concentration of 15 g l−1, 30°C, pH 5.5 and a dilution rate of 1.24 h−1. Adding 10 g l−1 YE and 2 g l−1 polypeptone, other inducers were unnecessary to maintain production of nisin. The operating conditions of the reactor removed
nisin and lactate, thus minimizing their effects which allowed the maintenance of cells in continuous exponential growth phase
mode with high metabolic activity. 相似文献
5.
Factors affecting the growth of Fusarium proliferatum and the production of fumonisin B1: oxygen and pH 总被引:1,自引:0,他引:1
S E Keller T M Sullivan S Chirtel 《Journal of industrial microbiology & biotechnology》1997,19(4):305-309
Fumonisins are mycotoxins produced primarily by Fusarium moniliforme and Fusarium proliferatum in corn. In liquid culture, production of fumonisin B1 (FB1), the most common moiety of the family of fumonisins, can be obtained using a defined medium that is nitrogen-limited. Under
nitrogen-limited conditions both growth and the production of FB1 were greatly influenced by pH and aeration. At pH above 5.0, F. proliferatum grew normally but produced little FB1 (<100 μg m−1). At pH below 5.0, there was less growth but substantially more FB1. Below a pH of 2.5, both growth and metabolism were slower with very little FB1 produced. When the optimal pH range of between 3.0 and 4.0 under well-aerated conditions was used, both growth and FB1 production were high. However, under oxygen-limited conditions, less growth occurred, glucose consumption was increased,
and no FB1 was produced.
Received 16 May 1997/ Accepted in revised form 03 September 1997 相似文献
6.
J-H Lee I-Y Lee M-K Kim Y-H Park 《Journal of industrial microbiology & biotechnology》1999,23(2):143-148
We sought an optimal pH profile to maximize curdlan production in a batch fermentation of Agrobacterium species. The optimal pH profile was calculated using a gradient iteration algorithm based on the minimum principle of Pontryagin.
The model equations describing cell growth and curdlan production were developed as functions of pH, sucrose concentration,
and ammonium concentration, since the specific rates of cell growth and curdlan production were highly influenced by those
parameters. The pH profile provided the strategy to shift the culture pH from the optimal growth condition (pH 7.0) to the
optimal production one (pH 5.5) at the time of ammonium exhaustion. By applying the optimal pH profile in the batch process,
we obtained significant improvement in curdlan production (64 g L−1) compared to that of constant pH operation (36 g L−1).
Received 24 November 1998/ Accepted in revised form 17 June 1999 相似文献
7.
The effect on nisin production of increasing nisin immunity/resistance genes in Lactococcus lactis subsp. lactis MG1363 was investigated. The 60-kb nisin immunity/resistance plasmid pND300, which was isolated from a non-nisin-producing
strain, encodes five genes involved in nisin immunity/resistance, which are very similar to those of the immunity/resistance
system encoded by the nisin-production transposon. The introduction of pND300 into MG1363(TnNip) resulted in the construct being able to produce significantly more nisin than the parent MG1363(TnNip). The introduction of pND314, which contains the nisin immunity/resistance genes subcloned into pSA3, into MG1363(TnNip) allowed the strain to grow more rapidly than the parent MG1363(TnNip) with a concomitant increase in the rate of nisin production. This work illustrates that introduction of pND300 and a derivative
containing the nisin immunity/resistance system of pND300 into MG1363 (TnNip) can result in significant alterations to the kinetics of nisin production. These observations indicate approaches that may
be used successfully to improve the economics of nisin production.
Received: 11 February 1998 / Received revision: 25 June 1998 / Accepted: 27 June 1998 相似文献
8.
S F Cavalitto R A Hours C F Mignone 《Journal of industrial microbiology & biotechnology》2000,25(5):260-265
Geotrichum klebahnii ATCC 42397 produces a protopectinase (PPase-SE) with polygalacturonase (PGase) activity. The microorganism was aerobically
cultivated in synthetic media. Glucose, fructose and xylose yielded the highest enzyme levels (10–11 PGase units ml−1). Galacturonic acid repressed enzyme production and no growth was obtained with disaccharides and pectin. Specific enzyme
activity obtained in an O2-limited culture was similar to that found in nonlimited ones. A growth yield (Y
x/s) of 0.49 g of cell dry weight per gram of glucose consumed was obtained in a typical batch bioreactor culture. Enzyme production
was growth associated, and no major products other than biomass and CO2 were detected. The volumetric enzyme activity reached a maximum around D=0.3–0.4 h−1 in glucose-limited continuous cultures. However, it varied strongly (together with microorganism morphology) even after retention
times ≥8 at any D tested (0.035–0.44 h−1) though the rest of the culture variables remained fairly constant. No correlation between morphology and enzyme activity
could be obtained. Enzyme production was poor in urea- and vitamin-limited continuous cultures. In all cases, biomass and
CO2 accounted for ≅100% of carbon recovery though Y
x/s values were different. Journal of Industrial Microbiology & Biotechnology (2000) 25, 260–265.
Received 20 April 2000/ Accepted in revised form 15 September 2000 相似文献
9.
W. Sabra A. -P. Zeng S. Sabry S. Omar W. -D. Deckwer 《Applied microbiology and biotechnology》1999,52(6):773-780
Alginate production by Azotobacter vinelandii was studied in batch and continuous cultures under microaerobic conditions. In batch culture at a pO2 of 2–3% (air saturation) alginate production was enhanced by decreasing the PO3−
4 level in the medium. Alginate yield from biomass (Y
P/X) reached the highest value of 0.66 g/g at the lowest phosphate level (100 mg/l), compared to 0.40 g/g and 0.25 g/g at higher
phosphate levels (200 mg/l and 400 mg/l, respectively). In contrast, biomass formation behaved differently and the growth
yield (Y
X/S) decreased with decreasing PO4
3− concentrations. Moreover, the respiratory quotient (RQ) of the culture was dependent on the initial phosphate concentration,
especially in the phosphate-limited phase of growth. As the initial phosphate level decreased from 400 mg/l to 100 mg/l, the
average RQ value of the culture declined from 1.46 to 0.89. The low RQ value is very close to the theoretical optimum RQ,
calculated to be 0.8 on the basis of the stoichiometry of the metabolic pathways for alginate formation from sucrose. This
optimum RQ was also confirmed in continuous culture at different dilution rates. Independent of the dilution rate, a pO2 value of 2–5% (air saturation) was found to be optimal for alginate production, the corresponding RQ values being 0.80–0.84.
In addition, the molecular mass and composition of alginate were also found to be affected by both phosphate and oxygen concentrations.
In conclusion, the RQ appears to be a useful parameter for optimum control of alginate production with this microorganism.
Received: 31 March 1999 / Received revision: 2 July 1999 / Accepted: 5 July 1999 相似文献
10.
D. Fabritius H. J. Schäfer A. Steinbüchel 《Applied microbiology and biotechnology》1996,45(3):342-348
The transformation of oleic acid by mutants of Candida tropicalis was studied in fed-batch cultures. Besides Δ9-cis–1,18-octadecenedioic acid, 3-hydroxy-Δ9-cis–1,18-octadecenedioic acid was detected as the main fermentation product. Here we describe the production, isolation and the
complete chemical characterization of the purified 3-hydroxy-Δ9-cis–1,18-octadecenedioic acid. The geometric configuration of the double bond was not changed during bioconversion. The enantiomeric
excess of the compound was 76%. Mutagenesis of C. tropicalis DSM 3152 with N-methyl-N-nitro-N′-nitrosoguanidine and selection with oleic acid as the sole carbon source led to mutant M 25, which produced the 3-hydroxy-Δ9-cis–1,18-octadecenedioic acid at a 1.8-fold higher concentration in the medium as compared to the parent strain. The maximum
concentration of the hydroxy dioic acid was 19.4 g/l after 223 h fermentation.
Received: 24 August 1995/Received revision: 21 September 1995/Accepted: 4 October 1995 相似文献
11.
Optimization of culture medium for the continuous cultivation of the microalga Haematococcus pluvialis 总被引:4,自引:0,他引:4
Fábregas J Domínguez A Regueiro M Maseda A Otero A 《Applied microbiology and biotechnology》2000,53(5):530-535
The freshwater microalga Haematococcus pluvialis is one of the best microbial sources of the carotenoid astaxanthin, but this microalga shows low growth rates and low final
cell densities when cultured with traditional media. A single-variable optimization strategy was applied to 18 components
of the culture media in order to maximize the productivity of vegetative cells of H. pluvialis in semicontinuous culture. The steady-state cell density obtained with the optimized culture medium at a daily volume exchange
of 20% was 3.77 · 105 cells ml−1, three times higher than the cell density obtained with Bold basal medium and with the initial formulation. The formulation
of the optimal Haematococcus medium (OHM) is (in g l−1) KNO3 0.41, Na2HPO4 0.03, MgSO4 · 7H2O 0.246, CaCl2 · 2H2O 0.11, (in mg l−1) Fe(III)citrate · H2O 2.62, CoCl2 · 6H2O 0.011, CuSO4 · 5H2O 0.012, Cr2O3 0.075, MnCl2 · 4H2O 0.98, Na2MoO4 · 2H2O 0.12, SeO2 0.005 and (in μg l−1]) biotin 25, thiamine 17.5 and B12 15. Vanadium, iodine, boron and zinc were demonstrated to be non-essential for the growth of H. pluvialis. Higher steady-state cell densities were obtained by a three-fold increase of all nutrient concentrations but a high nitrate
concentration remained in the culture medium under such conditions. The high cell productivities obtained with the new optimized
medium can serve as a basis for the development of a two-stage technology for the production of astaxanthin from H. pluvialis.
Received: 10 September 1999 / Received revision: 2 December 1999 / Accepted: 3 December 1999 相似文献
12.
The generation time ofP. mirabilis in defined and in complex medium is shorter in the presence of hydrogen acceptors than in their absence. In the presence
of hydrogen acceptors the molar growth yield for glucose and the acetate production are strongly increased. From the molar
growth yield and the acetate production YATP in defined medium was calculated as 5.5 g/mole, whereas in complex medium a value of 12.6 g/mole was obtained. The molar
growth yield, the acetate production, the amount of hydrogen acceptor reduced and YATP were used to calculate P/2e−ratios for phosphorylation coupled to electron transfer to oxygen, nitrate and tetrathionate as respectively 2.80; 1.48 and
1.23 in defined medium. Under anaerobic conditions in the presence of nitrate or tetrathionate as hydrogen acceptor in complex
medium a bend in the growth curve is observed. In the period of rapid growth the P/2e−ratio for nitrate reduction is of the same magnitude as that in defined medium, however much lower P/2e−ratios are found during the subsequent period of slow growth. The P/2e−ratios for tetrathionate reduction in complex medium for both growth periods are lower than those in defined medium. Most
probably these results indicate that during this period growth and energy production are uncoupled. Under aerobic conditions
in complex medium a constant YO value of 32.2 g/atom O is found during a short period of the growth curve. Afterwards when the cell density increases a steady
decrease of YO is observed. 相似文献
13.
Trichoderma reesei endoglucanase I (EGI) was used as a reporter enzyme for screening mutagenized yeast strains for increased ability to produce
protein. Sixteen haploid Saccharomyces cerevisiae strains, transformed with a yeast multicopy vector pALK222, containing the EGI cDNA under the ADH1 promoter, produced EGI activity of 10-5–10-4 g/l. On the average 93% of the total activity was secreted into the culture medium. Two strains with opposite mating types
were mutagenized, and several mutants were isolated possessing up to 45-fold higher EGI activity. The best mutants were remutagenized
and a second-generation mutant, strain 2804, with an additional twofold increase in EGI activity was selected. The mutant
strain 2804 grew more slowly and reached a lower final cell density than the parental strain. In the selective minimal medium,
the 2804 strain produced 40 mg/l immunoreactive EGI protein, but only 2% was active enzyme. In the rich medium the secreted
EGI enzyme stayed active, but without selection pressure the EGI production ceased after 2 days of cultivation, when the strain
2804 had produced 10 mg/l of EGI. A sevenfold difference was found between the parental and the 2804 strain in their total
EGI production relative to cell density. The difference in favour of the mutant strain was also detected on the mRNA level.
The 2804 mutant was found to be more active than the parental strain also in the production of T. reesei cellulases, cellobiohydrolase I, and cellobiohydrolase II.
Received: 22 December 1995/Received revision: 26 February 1996/Accepted: 17 March 1996 相似文献
14.
Increased astaxanthin production by a Phaffia rhodozyma mutant grown on date juice from Yucca fillifera 总被引:1,自引:0,他引:1
J Ramírez M L Nuñez R Valdivia 《Journal of industrial microbiology & biotechnology》2000,24(3):187-190
The wild strain and the astaxanthin-overproducing mutant strain 25–2 of Phaffia rhodozyma were analyzed in order to assess their ability to grow and synthesize astaxanthin in a minimal medium composed of g L−1: KH2PO4 2.0; MgSO4 0.5; CaCl2 0.1; urea 1.0 and supplemented with date juice of Yucca fillifera as a carbon source (yuca medium). The highest astaxanthin production (6170 μg L−1) was obtained at 22.5 g L−1 of reducing sugars. The addition of yeast extract to the yuca medium at concentrations of 0.5–3.0 g L−1 inhibited astaxanthin synthesis. The yuca medium supported a higher production of astaxanthin, 2.5-fold more than that observed
in the YM medium. Journal of Industrial Microbiology & Biotechnology (2000) 24, 187–190.
Received 14 July 1999/ Accepted in revised form 02 December 1999 相似文献
15.
Pseudomonas putida NCIMB 11767 oxidized phenol, monochlorophenols, several dichlorophenols and a range of alkylbenzenes (C1–C6) via an inducible toluene dioxygenase enzyme system. Biphenyl and naphthalene were also oxidized by this enzyme. Growth on
toluene and phenol induced the meta-ring-fission enzyme, catechol 2,3-oxygenase, whereas growth on benzoate, which did not require expression of toluene dioxygenase,
induced the ortho-ringcleavage enzyme, catechol 1,2-oxygenase. Monochlorobenzoate isomers and 2,3,5-trichlorophenol were gratuitous inducers
of toluene dioxygenase, whereas 3,4-dichlorophenol was a fortuitous oxidation substrate of the enzyme. The organism also grew
on 2,4- and 2,5-dichloro isomers of both phenol and benzoate, on 2,3,4-trichlorophenol and on 1-phenylheptane. During growth
on toluene in nitrogen-limited chemostat culture, expression of both toluene dioxygenase and catechol 2,3-oxygenase was positively
correlated with increase in specific growth rate (0.11–0.74 h-1), whereas the biomass yield coefficient decreased. At optimal dilution rates, the predicted performance of a 1-m3 bioreactor supplied with 1 g nitrogen l-1 for removal of toluene was 57 g day-1 and for removal of trichloroethylene was 3.4 g day-1. The work highlights the oxidative versatility of this bacterium with respect to substituted hydrocarbons and shows how growth
rate influences the production of competent cells for potential use as bioremediation catalysts.
Received: 26 June 1995 / Received revision: 4 September 1995 / Accepted: 20 September 1995 相似文献
16.
Earthworm secondary production and N flux in agroecosystems: a comparison of two approaches 总被引:1,自引:0,他引:1
Production was estimated for Aporrectodea spp. and Lumbricus spp. populations in corn agroecosystems with a 5-year history of manure or inorganic fertilizer applications during 1994–1995
and 1995–1996. Earthworm biomass and production were greater in manure than inorganic fertilizer plots, although biomass and
production declined by about 50% between 1994–1995 and 1995–1996 due to unfavorable climatic conditions. Production was highest
during the spring and autumn when soil temperatures were between 4 and 22°C. Production was higher in Lumbricus spp. than Aporrectodea spp. populations due to greater Lumbricus spp. biomass. Aporrectodea spp. production was 3.47–16.14 g ash-free dry weight (AFDW) m–2 year–1, while Lumbricus spp. production was 6.09–18.11 g AFDW m–2 year–1, depending on the fertilizer treatment and the method used to estimate production. However, production estimates from the
instantaneous growth rate method were within 27% of the values calculated using the size-frequency method. Nitrogen flux through
earthworms was used to estimate efficiency quotients. Net production efficiency (P/A) ranged from 0.64 to 0.76, assimilation efficiency (A/C) ranged from 0.1 to 0.3, and gross production efficiency (P/C) ranged from 0.06 to 0.22. Annual N flux through earthworm populations was higher in manure than inorganic fertilizer plots,
and ranged from 2.95 to 5.47 g N m–2 year–1 in 1994–1995 and 1.76 to 2.92 g N m–2 year–1 in 1995–1996. The N flux through earthworms represented an amount equivalent to 16–30% of crop N uptake during 1994–1995
and 11–18% of crop N uptake during 1995–1996. We concluded that the effects of earthworms on N cycling in corn agroecosystems
were substantial, and that N flux through earthworms was influenced significantly by fertilizer amendments.
Received: 20 September 1999 / Accepted: 24 March 2000 相似文献
17.
The time courses of growth and rosmarinic acid production by Lavandula vera MM cell suspension were investigated. The uptake of the main nutrients (sucrose, nitrogen, phosphorus, K, Ca, Mg) was followed
during cultivation and the data on the physiology of the L. vera MM cell culture are presented. It was established that the cell culture synthesizes rosmarinic acid during the linear phase
of growth for a relatively short period (between the 4th and 8th days of cultivation). The influence of sucrose concentration
in the nutrient medium on cell growth and accumulation of rosmarinic acid by L. vera MM cell culture was investigated. The results showed that 7% sucrose in the nutrient medium ensured a steady growth of the
cell suspension and increased the yield of rosmarinic acid (29.2 g/l dry biomass and 507.5 mg/l rosmarinic acid compared to
13.0 g/l dry biomass and 68.6 mg/l rosmarinic acid for the control cultivation with 3% sucrose).
Received: 17 September 1996 / Received revision: 31 January 1997 / Accepted: 1 February 1997 相似文献
18.
Cultivation of the extreme thermophilic anaerobic bacterium Thermotoga thermarum at 77°C on xylan was accompanied by the formation of heat-stable endoxylanase (136U/l), β-xylosidase (44U/l) and α-arabinofuranosidase
(10U/l). These enzymes were mainly associated with the cells and could not be released by detergent treatment {0.1–1.0mM 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulphonate
(CHAPS)}. Endoxylanases with a molecular weight of 40, 83 and 100kDa were induced when xylan or xylose were used as substrates
for growth. In the presence of other sugars like glucose, maltose, arabinose or starch, low concentrations of the low-molecular-weight
endoxylanase (40kDa) was detected. Xylose was found to be the best substrate for the induction of β-xylosidase and α-arabinofuranosidase
but not for growth. Cultivation of T. thermarum in a dialysis batch fermentor resulted in a significant increase in cell concentration and enzyme level. A total cell count
of 1.3×109 cells/ml and 202U/l of endoxylanase were measured when partially soluble birchwood xylan was used as the carbon source. The
use of insoluble beechwood xylan as the substrate caused the elevation of the maximal cell concentration and enzyme level
up to 2.0×109 cells/ml and 540U/l, respectively.
Received: 14 September 1995/Received revision: 15 December 1995/Accepted: 18 December 1995 相似文献
19.
Valentina N. Khmelenina Marina G. Kalyuzhnaya Natalia G. Starostina Natalia E. Suzina Yuri A. Trotsenko 《Current microbiology》1997,35(5):257-261
Two strains (5Z and 20Z) of halotolerant alkaliphilic obligate methanotrophic bacteria were first isolated from moderately
saline soda lakes in Tuva (Central Asia). The strains grow fastest at pH 9.0–9.5 and much more slowly at pH 7.0. No growth
occurred at pH ≤ 6.8. They require NaHCO3 or NaCl for growth in alkaline medium. Gram-negative, motile rods with ordered cup-shaped cell wall structures and Type I
intracytoplasmic membranes assimilate methane and methanol via the ribulose monophosphate pathway. The G + C content of strains
5Z and 20Z are 47.6 and 47.9 mol%, respectively. Based on their alkaliphilic physiology, both strains were referred to as
Methylobacter alcaliphilus sp. nov. The changes in cell phospholipids, fatty acids, and amino acids have been observed upon varying salinity and pH
of the medium, thus suggesting structure-function osmoadaptation of the strains studied. Whole-cell experiments revealed the
salt- and pH-dependence of CH4 oxidation and assimilation rates. Cell motility was also Na+ dependent and sensitive to some energy uncouplers and ionophores.
Received: 7 March 1997 / Accepted: 14 April 1997 相似文献
20.
Two homofermentative strains, Lactobacillus casei NRRL B-441 and Lactobacillus casei subsp. rhamnosus NRRL B-445 were selected for further study from 17 lactic acid bacterial strains screened for lactic acid production. The
effect of temperature on lactic acid production with the selected strains was investigated by adapting both strains to four
different temperatures. The production of L(+)-lactic acid by both strains was most efficient at 37°C, although with L. casei the highest lactic acid concentration was obtained at 41°C. The maximal volumetric productivity with L. casei was 4.1 g l-1 h-1 and with L. casei subsp. rhamnosus 3.5 g l-1 h-1. The composition of the medium was studied in order to replace the costly yeast extract with less expensive sources of nitrogen
and amino acids. From 11 different nitrogen sources investigated at 37°C, barley malt sprouts (88 g l-1 lactic acid in 66 h) and grass extract (74 g l-1 lactic acid in 73 h) were the best economic alternatives. The effect of different combinations of yeast extract, peptone
and malt sprouts was further studied by using statistical experimental design, and an empirical second-order polynomial model
was constructed on the basis of the results. With the right combination most of the yeast extract could be substituted by
barley malt sprouts for efficient lactic acid production. A method for extraction of nutrients and growth factors from malt
sprouts is also described.
Received: 25 September 1995/Accepted: 24 October 1995 相似文献