Factors affecting exocellular polysaccharide production by Lactobacillus delbrueckii subsp. bulgaricus grown in a chemically defined medium

We developed a chemically defined medium (CDM) containing lactose or glucose as the carbon source that supports growth and exopolysaccharide (EPS) production of two strains of Lactobacillus delbrueckii subsp. bulgaricus. The factors found to affect EPS production in this medium were oxygen, pH, temperature, and medium constituents, such as orotic acid and the carbon source. EPS production was greatest during the stationary phase. Composition analysis of EPS isolated at different growth phases and produced under different fermentation conditions (varying carbon source or pH) revealed that the component sugars were the same. The EPS from strain L. delbrueckii subsp. bulgaricus CNRZ 1187 contained galactose and glucose, and that of strain L. delbrueckii subsp. bulgaricus CNRZ 416 contained galactose, glucose, and rhamnose. However, the relative proportions of the individual monosaccharides differed, suggesting that repeating unit structures can vary according to specific medium alterations. Under pH-controlled fermentation conditions, L. delbrueckii subsp. bulgaricus strains produced as much EPS in the CDM as in milk. Furthermore, the relative proportions of individual monosaccharides of EPS produced in pH-controlled CDM or in milk were very similar. The CDM we developed may be a useful model and an alternative to milk in studies of EPS production.     

Factors Affecting Exocellular Polysaccharide Production by Lactobacillus delbrueckii subsp. bulgaricus Grown in a Chemically Defined Medium

We developed a chemically defined medium (CDM) containing lactose or glucose as the carbon source that supports growth and exopolysaccharide (EPS) production of two strains of Lactobacillus delbrueckii subsp. bulgaricus. The factors found to affect EPS production in this medium were oxygen, pH, temperature, and medium constituents, such as orotic acid and the carbon source. EPS production was greatest during the stationary phase. Composition analysis of EPS isolated at different growth phases and produced under different fermentation conditions (varying carbon source or pH) revealed that the component sugars were the same. The EPS from strain L. delbrueckii subsp. bulgaricus CNRZ 1187 contained galactose and glucose, and that of strain L. delbrueckii subsp. bulgaricus CNRZ 416 contained galactose, glucose, and rhamnose. However, the relative proportions of the individual monosaccharides differed, suggesting that repeating unit structures can vary according to specific medium alterations. Under pH-controlled fermentation conditions, L. delbrueckii subsp. bulgaricus strains produced as much EPS in the CDM as in milk. Furthermore, the relative proportions of individual monosaccharides of EPS produced in pH-controlled CDM or in milk were very similar. The CDM we developed may be a useful model and an alternative to milk in studies of EPS production.     

Exopolysaccharide production by Streptococcus thermophilus SY: production and preliminary characterization of the polymer

AIMS: To evaluate the effect of yeast extract (YE) concentration, temperature and pH on growth and exopolysaccharide (EPS) production in a whey-based medium by Streptococcus thermophilus SY and to characterize the partially purified EPS. METHODS AND RESULTS: Factorial experiments and empirical model building were used to optimize fermentation conditions and the chemical composition, average molecular weight (MW) and rheological properties of aqueous dispersions of the EPS were determined. Exopolysaccharide production was growth associated and was higher (152 mg l(-1)) at pH 6.4 and 36 degrees C with 4 g l(-1) YE. High performance size exclusion chromatography of the partially purified EPS showed two peaks, with a weight average MW of 2 x 10(6) and 5 x 10(4), respectively. The EPS was a heteropolysaccharide, with a glucose : galactose : rhamnose ratio of 2 : 4.5 : 1. Its water dispersions had a pseudoplastic behaviour and showed a higher viscosity of xanthan solutions. SIGNIFICANCE AND IMPACT OF THE STUDY: The fermentation conditions and some properties of an EPS produced by Strep. thermophilus, a dairy starter organism, were described.     

Combined effects of temperature and medium composition on exopolysaccharide production by Lactobacillus rhamnosus RW-9595M in a whey permeate based medium

The effects of temperature (22-42 degrees C), whey permeate concentration (WP, 1.6-8.4%), and supplementation level with yeast nitrogen base (YNB, 0-2.0%) on exopolysaccharide (EPS) production was studied during 20 pH-controlled (pH = 6.0) batch cultures with Lactobacillus rhamnosus RW-9595M, using a central composite design (CCD). The EPS production was measured using both the conventional method based on ethanol precipitation of EPS and a new ultrafiltration (UF) method. EPS production was not growth-associated for high temperatures (32-42 degrees C) and WP concentrations (7.0-8.4%). In contrast, at suboptimal temperature (22-26 degrees C), EPS production was growth-associated. Maximal EPS production measured with the UF method was approximately 2-fold higher than those measured with the conventional method and varied from 125 to 477 mg/L. This parameter was significantly influenced by WP and YNBWP interaction, whereas ANOVA for maximal EPS production measured by the conventional method did not show significant factor effects. EPS volumetric productivities varied from 3.0 to 16.4 mg EPS/L small middle doth. YNB supplementation did not promote cell growth but did increase EPS production at high WP concentrations. Our data indicate the potential of L. rhamnosus RW-9595M for producing EPS in a supplemented WP medium and suggest that this production could be further increased by the addition of a growth-limiting nutrient in the medium.     

Culture conditions determine the balance between two different exopolysaccharides produced by Lactobacillus pentosus LPS26

Lactobacillus pentosus LPS26, isolated from a natural fermentation of green olives, produces a capsular polymer constituted of two exopolysaccharides (EPS): EPS A, a high-molecular-weight (high-Mw) polysaccharide (1.9x10(6) Da) composed of glucose and rhamnose (3:1), and EPS B, a low-Mw polysaccharide (3.3x10(4) Da) composed of glucose and mannose (3:1). Fermentation experiments in a chemically semidefined medium with different carbon sources (glucose, fructose, mannitol, and lactose) showed that all of them except fructose supported EPS A production rather than EPS B production. The influence of temperature and pH was further analyzed. As the temperature dropped, increased synthesis of both EPS was detected. The control of pH especially enhanced EPS B production. With regard to this, the maximum total EPS production (514 mg liter-1) was achieved at a suboptimal growth temperature (20 degrees C) and pH 6.0. Continuous cultures showed that EPS A, synthesized mainly at low dilution rates, is clearly dependent on the growth rate, whereas EPS B synthesis was hardly affected. EPS production was also detected in supplemented skimmed milk, but no increase on the viscosity of the fermented milk was recorded. This could be linked to the high proportion of the low-Mw polysaccharide produced in these conditions in contrast to that observed in culture media. Overall, the present study shows that culture conditions have a clear impact on the type and concentration of EPS produced by strain LPS26, and consequently, these conditions should be carefully selected for optimization and application studies. Finally, it should be noted that this is, to our knowledge, the first report on EPS production by L. pentosus.     

Study of the effects of temperature, pH and yeast extract on growth and exopolysaccharides production by Propionibacterium acidi-propionici on milk microfiltrate using a response surface methodology

AIMS: To study the effects of temperature, pH and yeast extract (YE) concentration on growth and exopolysaccharide (EPS) production by Propionibacterium acidi-propionici DSM 4900 cultivated on milk microfiltrate. METHODS AND RESULTS: A multifactorial approach using a Response Surface Methodology (RSM) was followed. The results indicated that both growth, and EPS and organic acids production, were influenced by pH, temperature and YE concentration. Biomass and organic acids production occurred in all the tested domains, whereas EPS production was only possible in a narrow pH range (5.3-6.5). The results clearly showed that the optimal conditions for EPS production were different to those for optimal growth. The effect of YE on EPS production was not only due to an increase in growth but also to a direct effect on the production of EPS. The temperature played a major role. A decrease of temperature induced a slowing down of both growth and organic acids production, making the essential factors of the medium and the precursors of EPS biosynthesis more available and hence, leading to an increase in EPS production. CONCLUSION: The effects of pH, temperature and YE were determined, allowing the definition of favourable, though non-optimal, conditions for EPS production: 23 degrees C, pH 6 and 3 g l(-1) YE concentration. SIGNIFICANCE AND IMPACT OF THE STUDY: The use of a multifactorial approach for investigating the effect of fermentation conditions on EPS production has been demonstrated.     

Culture Conditions Determine the Balance between Two Different Exopolysaccharides Produced by Lactobacillus pentosus LPS26

Lactobacillus pentosus LPS26, isolated from a natural fermentation of green olives, produces a capsular polymer constituted of two exopolysaccharides (EPS): EPS A, a high-molecular-weight (high-M_w) polysaccharide (1.9 × 10⁶ Da) composed of glucose and rhamnose (3:1), and EPS B, a low-M_w polysaccharide (3.3 × 10⁴ Da) composed of glucose and mannose (3:1). Fermentation experiments in a chemically semidefined medium with different carbon sources (glucose, fructose, mannitol, and lactose) showed that all of them except fructose supported EPS A production rather than EPS B production. The influence of temperature and pH was further analyzed. As the temperature dropped, increased synthesis of both EPS was detected. The control of pH especially enhanced EPS B production. With regard to this, the maximum total EPS production (514 mg liter⁻¹) was achieved at a suboptimal growth temperature (20°C) and pH 6.0. Continuous cultures showed that EPS A, synthesized mainly at low dilution rates, is clearly dependent on the growth rate, whereas EPS B synthesis was hardly affected. EPS production was also detected in supplemented skimmed milk, but no increase on the viscosity of the fermented milk was recorded. This could be linked to the high proportion of the low-M_w polysaccharide produced in these conditions in contrast to that observed in culture media. Overall, the present study shows that culture conditions have a clear impact on the type and concentration of EPS produced by strain LPS26, and consequently, these conditions should be carefully selected for optimization and application studies. Finally, it should be noted that this is, to our knowledge, the first report on EPS production by L. pentosus.     

New method for exopolysaccharide determination in culture broth using stirred ultrafiltration cells

A new method to remove simple carbohydrates from culture broth prior to the quantification of exopolysaccharides (EPS) was developed and validated for the EPS-producing strain, Lactobacillus rhamnosus RW-9595M. This method uses ultrafiltration (UF) in stirred cells followed by polysaccharide detection in the retentate by the phenol-sulfuric acid method. The UF method was compared with a conventional method based on ethanol extraction, dialysis, protein removal by trichloroacetic acid (TCA) and freeze-drying. EPS production during pH-controlled batch fermentations in basal minimum medium, whey permeate (WP). and whey permeate supplemented with yeast extract, minerals and Tween-80 (SWP) was determined by the new UF and conventional methods. EPS recovery by the new method ranged from 83% to 104% for EPS added in the concentration range 40-1,500 mg/l in 0.1 M NaCl solution or culture medium. The UF method was rapid (8 h), accurate and simple, and required only a small sample volume (1-5 ml). A very high maximum EPS production was measured in SWP by both the UF and conventional methods (1,718 and 1,755 mg/l).     

Production of bakers' yeast in cheese whey ultrafiltrate

A process for the production of bakers' yeast in whey ultrafiltrate (WU) is described. Lactose in WU was converted to lactic acid and galactose by fermentation. Streptococcus thermophilus was selected for this purpose. Preculturing of S. thermophilus in skim milk considerably reduced its lag. Lactic fermentation in 2.3x-concentrated WU was delayed compared with that in unconcentrated whey, and fermentation could not be completed within 60 h. The growth rate of bakers' yeast in fermented WU differed among strains. The rate of galactose utilization was similar for all strains, but differences in lactic acid utilization occurred. Optimal pH ranges for galactose and lactic acid utilization were 5.5 to 6.0 and 5.0 to 5.5, respectively. The addition of 4 g of corn steep liquor per liter to fermented WU increased cell yields. Two sources of nitrogen were available for growth of Saccharomyces cerevisiae: amino acids (corn steep liquor) and ammonium (added during the lactic acid fermentation). Ammonium was mostly assimilated during growth on lactic acid. This process could permit the substitution of molasses by WU for the industrial production of bakers' yeast.     

Bacteriocin production by strain <Emphasis Type="Italic">Lactobacillus delbruecki</Emphasis>i ssp. <Emphasis Type="Italic">bulgaricus</Emphasis> BB18 during continuous prefermentation of yogurt starter culture and subsequent batch coagulation of milk

By screening for bacteriocin-producing lactic acid bacteria of 1,428 strains isolated from authentic Bulgarian dairy products, Lb. bulgaricus BB18 strain obtained from kefir grain was selected. Out of 11 yogurt starters containing Lb. bulgaricus BB18 and S. thermophilus strains resistant to bacteriocin secreted by Lb. bulgaricus BB18 a yogurt culture (S. thermophilus 11A+Lb. bulgaricus BB18) with high growth and bacteriocinogenic activity in milk was selected. Continuous (pH-stat 5.7) prefermentation processes were carried out in milk at 37 degrees C in a 2l MBR bioreactor (MBR AG, Zurich, Switzerland) with an IMCS controller for agitation speed, temperature, dissolved oxygen, CO2 and pH. Prefermented milk with pH 5.7 coagulated in a thermostat at 37 degrees C until pH 4.8-4.9. S. thermophilus 11A and Lb. bulgaricus BB18 grew independently in a continuous mode at similar and sufficiently high-dilution rates (D=1.83 h(-1)-S. thermophilus 11A; D=1.80 h(-1)-Lb. bulgaricus BB18). The yogurt cultures developed in a stream at a high-dilution rate (D=2.03-2.28 h(-1)). The progress of both processes (growth and bacteriocin production) depended on the initial ratio between the two microorganisms. The continuous prefermentation process promoted conditions for efficient fermentation and bacteriocinogenesis of the starter culture during the batch process: strong reduction of the times for bacteriocin production and coagulation of milk (to 4.5-5.0 h); high cell productivity (lactobacilli-4x10(12) CFU ml(-1), streptococci-6x10(12) CFU ml(-1)); high productivity of bacteriocins (4,500 BU ml(-1))-1.7 times higher than the bacteriocinogenic activity of the batch starter culture.     

Studies on batch production of bacterial concentrates from mixed species lactic starters

Optimum growth conditions for mixed species starter FDs 0172 at constant pH in skim milk, whey, and tryptone medium were investigated. Growth rate and maximum population were optimal at 30 C. pH values between 5.5 and 7.0 did not influence the growth rate and maximum population obtainable. Lactic acid-producing activity declined rapidly after reaching the end of the exponential growth phase. The bacterial balance was found to be influenced by the growth parameters: media, pH, temperature, and neutralizer. Skim milk or whey medium at 25 C, pH 6.5, and neutralized with 20% (vol/vol) NH₄OH kept the bacterial balance almost constant throughout the cultivation. Grown in tryptone medium at constant pH, the changes in bacterial balance and other metabolic activities were striking compared to the other two media tested. The effect of lactate as an inhibitor was found to be complex, changing with the growth conditions. Concentrates made from mixed species starters FDs 0172, FD 0570, CH 0170, CHs 0170, and T 27 were comparable to controls when cultivated at the optimum conditions found and thereafter centrifuged. Aroma production, proteolytic activity, and CO₂ production did not change significantly compared to controls when cultivated at optimum conditions in skim milk or whey medium.     

Genetic diversity and technological properties of Streptococcus thermophilus strains isolated from dairy products

AIMS: To evaluate the genetic diversity and the technological properties of 44 strains of Streptococcus thermophilus isolated from dairy products. Methods METHODS AND RESULTS: Strains were analysed for some relevant technological properties, i.e. exopolysaccharide (EPS) production, growth kinetic in skim milk medium, urease activity and galactose fermentation. The EPS production, determined by evaluating the colour of the colonies grown in ruthenium red milk agar, was observed in 50% of the analysed strains. Urease activity, determined by colorimetric and conductimetric methods, showed that 91% of the isolates, all except four, could hydrolyse urea. A conductimetric approach was also used for the evaluation of the overall metabolic behaviour in milk of Strep. thermophilus strains and the differences observed allowed grouping of the strains in seven different clusters. A total of 11 strains were able to produce acid in presence of galactose. Genetic diversity of Streptococcus thermophilus strains, evaluated by Random Amplified Polymorphic DNA fingerprinting (RAPD) and amplified epsC-D restriction analysis, allowed the identification of 21 different genotypes. CONCLUSIONS: Comparison between the genotypic and phenotypic data highlights an interesting correlation between some important technological properties and well-defined genotypes. SIGNIFICANCE AND IMPACT OF THE STUDY: The genetic and technological characterization carried out on several Strep. thermophilus strains of dairy origin should expand the knowledge on this important lactic acid bacteria species and lead to a simple, rapid, and reliable identification of strains on the basis of well-defined biotechnological properties.     

Production of exopolysaccharides by Agrobacterium sp. CFR-24 using coconut water - a byproduct of food industry

AIMS: The work is intended to explore the suitability of underutilized coconut water (a byproduct of food industry) for the production of exopolysaccharides (EPS) by Agrobacterium sp. CFR 24. METHODS AND RESULTS: Besides checking the suitability of coconut water for the production of water-soluble (WS) and water-insoluble (WIS) EPS, certain fermentation parameters, such as initial pH, incubation period and kinetics of EPS production were investigated. The coconut water medium was found to support the production of both types of EPS. The optimal initial pH and temperature was found to be 6.0 and 30 degrees C, respectively. In shake flask (150 rev min(-1)) studies, high-cell density inoculum resulted in the production of 11.50 g l(-1) of WIS-EPS and 4.01 g l(-1) WS-EPS after 72 and 96 h of fermentation, respectively. CONCLUSIONS: Coconut water was found suitable for the production of microbial EPS by Agrobacterium sp. CFR 24 strain. Under optimum conditions, it produced a good amount of WIS-EPS, which is comparable with that of the sucrose medium (11 g l(-1)). SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report on the use of coconut water as a fermentation medium for the production of any microbial EPS. Besides producing value-added products, use of this food industry byproduct, which is often being drained out, can significantly reduce the problem of environmental pollution.     

Batch fermentation of whey ultrafiltrate by Lactobacillus helveticus for lactic acid production

Summary Cheese whey ultrafiltrate (WU) was used as the carbon source for the production of lactic acid by batch fermentation with Lactobacillus helveticus strain milano. The fermentation was conducted in a 400 ml fermentor at an agitation rate of 200 rpm and under conditions of controlled temperature (42° C) and pH. In the whey ultrafiltrate-corn steep liquor (WU-CSL) medium, the optimal pH for fermentation was 5.9. Inoculum propagated in skim milk (SM) medium or in lactose synthetic (LS) medium resulted in the best performance in fermentation (in terms of growth, lactic acid production, lactic acid yield and maximum productivity of lactic acid), as compared to that propagated in glucose synthetic (GS) medium. The yeast extract ultrafiltrate (YEU) used as the nitrogen/growth factor source in the WU medium at 1.5% (w/v) gave the highest maximum productivity of lactic acid of 2.70 g/l-h, as compared to the CSL and the tryptone ultrafiltrate (TU). L. helveticus is more advantageous than Streptococcus thermophilus and Lactobacillus delbrueckii for the production of lactic acid from WU. The L. helveticus process will provide an alternative solution to the phage contamination in dairy industries using Lactobacillus bulgaricus.     

Exopolysaccharide production during batch cultures with free and immobilized Lactobacillus rhamnosus RW-9595M

AIMS: Exopolysaccharides (EPS) were produced by Lactobacillus rhamnosus RW-9595M during pH-controlled batch cultures with free cells and repeated-batch cultures with cells immobilized on solid porous supports (ImmobaSil). METHODS AND RESULTS: Cultures were conducted in supplemented whey permeate (SWP) medium containing 5 or 8% (w/w) whey permeate. For free-cell batch cultures in 8% SWP medium, very high maximum cell counts (1.3 x 10(10) CFU ml(-1)) and EPS production (2350 mg l(-1)) were measured. A high EPS production (1750 mg l(-1)) was measured after four cycles for a short incubation period of only 7 h. Several methods for immobilized biomass determination based on analysis of biomass components (proteins, ATP and DNA) were tested. The DNA analysis method proved to be the most appropriate under these circumstances. This method revealed a high maximum immobilized biomass of 8.5 x 10(11) CFU ml(-1) support during repeated immobilized cell cultures in 5% SWP. The high immobilized biomass increased maximum EPS volumetric productivity (250 mg l(-1) h(-1) after 7 h culture) compared with free-cell batch cultures (110 mg l(-1) h(-1) after 18 h culture). CONCLUSIONS: High EPS productions were achieved during batch cultures of Lact. rhamnosus RW-9595M in SWP medium, exceeding 1.7 g EPS per litre. Repeated-batch cultures with immobilized cells resulted in increased EPS productivity compared with traditional free-cell cultures. SIGNIFICANCE AND IMPACT OF THE STUDY: The study clearly shows the high potential of the strain Lact. rhamnosus RW-9595M and immobilized cell technology for production of EPS as a functional food ingredient.     

Influence of Whey Protein Concentrate on the Production of Antibacterial Peptides Derived from Fermented Milk by Lactic Acid Bacteria

In the study, growth, proteolysis and antimicrobial activity of lactic acid bacteria were evaluated in skim milk medium supplemented with different concentration of whey protein concentrate (WPC 70). Lactobacillus helveticus (V3) showed maximum pH reduction with 1% WPC. Lactobacillus rhamnosus (NS4) also produced maximum lactic acid production and viable cells counts at 1 and 1.5% WPC, respectively. However, V3 showed maximum proteolytic activity with 1.5% WPC. Streptococcus thermophilus (MD2) was found to exhibit maximum antimicrobial activity with 1.5% WPC. Peptides formed during fermentation were purified by RP-HPLC and identified using RP-LC/MS analysis. Antimicrobial peptide was identified as lactoferrin, which was found in fermented milk supplemented with 1.5% WPC by NS4.     

Biodiversity of exopolysaccharides produced by Streptococcus thermophilus strains is reflected in their production and their molecular and functional characteristics

Twenty-six lactic acid bacterium strains isolated from European dairy products were identified as Streptococcus thermophilus and characterized by bacterial growth and exopolysaccharide (EPS)-producing capacity in milk and enriched milk medium. In addition, the acidification rates of the different strains were compared with their milk clotting behaviors. The majority of the strains grew better when yeast extract and peptone were added to the milk medium, although the presence of interfering glucomannans was shown, making this medium unsuitable for EPS screening. EPS production was found to be strain dependent, with the majority of the strains producing between 20 and 100 mg of polymer dry mass per liter of fermented milk medium. Furthermore, no straightforward relationship between the apparent viscosity and EPS production could be detected in fermented milk medium. An analysis of the molecular masses of the isolated EPS by gel permeation chromatography revealed a large variety, ranging from 10 to >2,000 kDa. A distinction could be made between high-molecular-mass EPS (>1,000 kDa) and low-molecular-mass EPS (<1,000 kDa). Based on the molecular size of the EPS, three groups of EPS-producing strains were distinguished. Monomer analysis of the EPS by high-performance anion-exchange chromatography with amperometric detection was demonstrated to be a fast and simple method. All of the EPS from the S. thermophilus strains tested were classified into six groups according to their monomer compositions. Apart from galactose and glucose, other monomers, such as (N-acetyl)galactosamine, (N-acetyl)glucosamine, and rhamnose, were also found as repeating unit constituents. Three strains were found to produce EPS containing (N-acetyl)glucosamine, which to our knowledge was never found before in an EPS from S. thermophilus. Furthermore, within each group, differences in monomer ratios were observed, indicating possible novel EPS structures. Finally, large differences between the consistencies of EPS solutions from five different strains were assigned to differences in their molecular masses and structures.     

Production of beta-galactosidase from Streptococcus thermophilus grown in whey.

beta-D-Galactosidase (EC 3.2.1.23) was extracted from Streptococcus thermophilus grown in deproteinized cheese whey. Cultural conditions optimum for maximum enzyme production were pH 7.0, 40 degrees C, and 24 h. Proteose peptone (2.0%, wt/vol) and corn steep liquor (2.8%, wt/vol) were highly stimulatory, increasing the enzyme units available in their absence from 660 U/liter of medium to 18,200 and 10,000 U/liter of medium, respectively, in their presence. There was an insignificant increase in the production of enzyme in the presence of added inorganic nitrogen and phosphorus sources. Enzymatic hydrolysis for recuction of lactose content in aqueous solution and in skim milk was studied.     

Production of beta-galactosidase from Streptococcus thermophilus grown in whey.

beta-D-Galactosidase (EC 3.2.1.23) was extracted from Streptococcus thermophilus grown in deproteinized cheese whey. Cultural conditions optimum for maximum enzyme production were pH 7.0, 40 degrees C, and 24 h. Proteose peptone (2.0%, wt/vol) and corn steep liquor (2.8%, wt/vol) were highly stimulatory, increasing the enzyme units available in their absence from 660 U/liter of medium to 18,200 and 10,000 U/liter of medium, respectively, in their presence. There was an insignificant increase in the production of enzyme in the presence of added inorganic nitrogen and phosphorus sources. Enzymatic hydrolysis for recuction of lactose content in aqueous solution and in skim milk was studied.     

Optimization of a new heteropolysaccharide production by a native isolate of Leuconostoc sp. CFR-2181

Aim:  This work is aimed at optimizing the production of a new heteropolysaccharide (HePS) of Leuconostoc sp. CFR-2181 by standardizing the fermentation conditions in a low cost semi-synthetic medium.
Methods and Results:  Both nutritional and cultural parameters, such as carbon source and its concentration, initial pH of the exopolysaccharide (EPS) medium, fermentation temperature and fermentation period were optimized. Fermentation of the EPS medium (pH 6·7), containing sucrose at 5% (w/v) and 5% (v/v) inoculum, at 25 ° C resulted in maximum production of HePS (18·38 g l⁻¹) by the isolate in 4 h of fermentation.
Conclusions:  The isolate was found to produce good amount of HePS in just 4 h in a low cost semi-synthetic EPS medium.
Significance and Impact of the Study:  This is the first report on rapid production of HePS by any lactic culture, which can significantly reduce the cost of the EPS.