Utilization of UF-permeate for production of beta-galactosidase by lactic acid bacteria

Four lactobacilli strains (Lactobacillus bulgaricus, Lactobacillus acidophilus, Lactobacilus casei and Lactobacillus reuteri) were grown in MRS broth and three lactococci strains (Streptococcus thermophilus, Lactococcus lactis subsp. Lactis and Lactococcus lactis subsp. lactis biovar. diacetilactis) were grown in M17 broth. L. reuteri and S. thermophilus were chosen on the basis of the best mean beta-galactosidase activity of 10.44 and 10.01 U/ml respectively, for further studies on permeate-based medium. The maximum production of beta-galactosidase by L. reuteri was achieved at lactose concentration of 6%, initial pH 5.0-7.5, ammonium phosphate as nitrogen source at a concentration of 0.66 g N/L and incubation temperature at 30 degrees C/24 hrs to give 6.31 U/ml. While in case of S. thermophilus, maximum beta-galactosidase production was achieved at 10% lactose concentration of permeate medium, supplemented with phosphate buffer ratio of 0.5:0.5 (KH2PO4:K2HPO4, g/L), at initial pH 6.0-6.5, ammonium phosphate (0.66g N/L) as nitrogen source and incubation temperature 35 degrees C for 24 hrs to give 7.85 U/ml.     

Lactobacillus growth and membrane composition in the presence of linoleic or conjugated linoleic acid

Five Lactobacillus strains of intestinal and food origins were grown in MRS broth or milk containing various concentrations of linoleic acid or conjugated linoleic acid (CLA). The fatty acids had bacteriostatic, bacteriocidal, or no effect depending on bacterial strain, fatty acid concentration, fatty acid type, and growth medium. Both fatty acids displayed dose-dependent inhibition. All strains were inhibited to a greater extent by the fatty acids in broth than in milk. The CLA isomer mixture was less inhibitory than linoleic acid. Lactobacillus reuteri ATCC 55739, a strain capable of isomerizing linoleic acid to CLA, was the most inhibited strain by the presence of linoleic acid in broth or milk. In contrast, a member of the same species, L. reuteri ATCC 23272, was the least inhibited strain by linoleic acid and CLA. All strains increased membrane linoleic acid or CLA levels when grown with exogenous fatty acid. Lactobacillus reuteri ATCC 55739 had substantial CLA in the membrane when the growth medium was supplemented with linoleic acid. No association between level of fatty acid incorporation into the membrane and inhibition by that fatty acid was observed.     

罗氏乳杆菌无细胞上清培养液移除胆固醇能力的研究

本文探讨了罗氏乳杆菌DSM122460无细胞上清培养液(Cell-Free Supernatant,CFS)移除胆固醇的能力。采用邻苯二甲醛法测定DSM122460和对照菌株ST-III发酵过程中及其CFS对胆固醇的移除能力,并研究不同CFS浓度下的移除能力。并采用HPLC法测定CFS对照、热处理组和pH7.0组的胆盐水解酶活力,同时测定其移除胆固醇能力。结果显示,DSM122460不仅在发酵过程中具有较高的移除胆固醇能力,其CFS也表现出较高的移除能力,CFS中含有除胆盐水解酶以外的可移除胆固醇的蛋白类成分。这提示可能存在一种乳酸菌移除胆固醇的新机制。     

Production of succinic Acid from citric Acid and related acids by lactobacillus strains

A number of Lactobacillus strains produced succinic acid in de Man-Rogosa-Sharpe broth to various extents. Among 86 fresh isolates from fermented cane molasses in Thailand, 30 strains (35%) produced succinic acid; namely, 23 of 39 Lactobacillus reuteri strains, 6 of 18 L. cellobiosus strains, and 1 of 6 unidentified strains. All of 10 L. casei subsp. casei strains, 5 L. casei subsp. rhamnosus strains, 6 L. mali strains, and 2 L. buchneri strains did not produce succinic acid. Among 58 known strains including 48 type strains of different Lactobacillus species, the strains of L. acidophilus, L. crispatus, L. jensenii, and L. parvus produced succinic acid to the same extent as the most active fresh isolates, and those of L. alimentarius, L. collinoides, L. farciminis, L. fructivorans (1 of 2 strains tested), L. malefermentans, and L. reuteri were also positive, to lesser extents. Diammonium citrate in de Man-Rogosa-Sharpe broth was determined as a precursor of the succinic acid produced. Production rates were about 70% on a molar basis with two fresh strains tested. Succinic acid was also produced from fumaric and malic acids but not from dl-isocitric, alpha-ketoglutaric, and pyruvic acids. The present study is considered to provide the first evidence on the production of succinic acid, an important flavoring substance in dairy products and fermented beverages, from citrate by lactobacilli.     

Quantitative real-time PCR analysis of fecal Lactobacillus species in infants receiving a prebiotic infant formula

The developing intestinal microbiota of breast-fed infants is considered to play an important role in the priming of the infants' mucosal and systemic immunity. Generally, Bifidobacterium and Lactobacillus predominate the microbiota of breast-fed infants. In intervention trials it has been shown that lactobacilli can exert beneficial effects on, for example, diarrhea and atopy. However, the Lactobacillus species distribution in breast-fed or formula-fed infants has not yet been determined in great detail. For accurate enumeration of different lactobacilli, duplex 5' nuclease assays, targeted on rRNA intergenic spacer regions, were developed for Lactobacillus acidophilus, Lactobacillus casei, Lactobacillus delbrueckii, Lactobacillus fermentum, Lactobacillus paracasei, Lactobacillus plantarum, Lactobacillus reuteri, and Lactobacillus rhamnosus. The designed and validated assays were used to determine the amounts of different Lactobacillus species in fecal samples of infants receiving a standard formula (SF) or a standard formula supplemented with galacto- and fructo-oligosaccharides in a 9:1 ratio (OSF). A breast-fed group (BF) was studied in parallel as a reference. During the 6-week intervention period a significant increase was shown in total percentage of fecal lactobacilli in the BF group (0.8% +/- 0.3% versus 4.1% +/- 1.5%) and the OSF group (0.8% +/- 0.3% versus 4.4% +/- 1.4%). The Lactobacillus species distribution in the OSF group was comparable to breast-fed infants, with relatively high levels of L. acidophilus, L. paracasei, and L. casei. The SF-fed infants, on the other hand, contained more L. delbrueckii and less L. paracasei compared to breast-fed infants and OSF-fed infants. An infant milk formula containing a specific mixture of prebiotics is able to induce a microbiota that closely resembles the microbiota of BF infants.     

Lactic acid bacteria fermentation of human milk oligosaccharide components, human milk oligosaccharides and galactooligosaccharides

Human milk contains about 7% lactose and 1% human milk oligosaccharides (HMOs) consisting of lactose with linked fucose, N-acetylglucosamine and sialic acid. In infant formula, galactooligosaccharides (GOSs) are added to replace HMOs. This study investigated the ability of six strains of lactic acid bacteria (LAB), Lactobacillus acidophilus, Lactobacillus plantarum, Lactobacillus fermentum, Lactobacillus reuteri, Streptococcus thermophilus and Leuconostoc mesenteroides subsp. cremoris, to digest HMO components, defined HMOs, and GOSs. All strains grew on lactose and glucose. N-acetylglucosamine utilization varied between strains and was maximal in L. plantarum; fucose utilization was low or absent in all strains. Both hetero- and homofermentative LAB utilized N-acetylglucosamine via the Embden-Meyerhof pathway. Lactobacillus acidophilus and L. plantarum were the most versatile in hydrolysing pNP analogues and the only strains releasing mono- and disaccharides from defined HMOs. Whole cells of all six LAB hydrolysed oNP-galactoside and pNP-galactoside indicating β-galactosidase activity. High β-galactosidase activity of L. reuteri, L. fermentum, S. thermophilus and L. mesenteroides subsp. cremoris whole cells correlated to lactose and GOS hydrolysis. Hydrolysis of lactose and GOSs by heterologously expressed β-galactosidases confirmed that LAB β-galactosidases are involved in GOS digestion. In summary, the strains of LAB used were not capable of utilizing complex HMOs but metabolized HMO components and GOSs.     

Polymer production by Lactobacillus delbrueckii ssp. bulgaricus

A polymer-forming strain of Lactobacillus delbrueckii ssp. bulgaricus was grown under differing conditions. It was found that at higher temperatures and slower growth the production of the polymer per cell was greater. Polymer-producing ability seems to be unstable with cells losing the phenotype faster at 48 than at 40°C. Specific production of polymer was increased in the presence of hydrolysed casein early in the growth phase when growing in milk, but production of polymer in MRS broth + lactose was reduced compared with milk. Furthermore, addition of hydrolysed casein to MRS did not increase specific production of polymer. Preliminary results suggest that the polymer is a glycoprotein, although the protein may be loosely associated with the carbohydrate.     

Lactobacilli isolated from sugary kefir grains capable of polysaccharide production and minicell formation

Homo- and heterofermentative species of Lactobacillus have been isolated from sugary kefir grains. Most of the homofermentative strains fermented tagatose and aldonitol and presented 48-54% of homology with Lactobacillus paracasei ssp. paracasei NCDO 151 (ex Lactobacillus casei). The two variants of a hetero-fermentative species, although fermenting arabinose, were related to Lactobacillus hilgardii NCDO 264 (type strain) with 88% of homology. One of them produced polysaccharide from sucrose at pH 4.8 and 30 degrees C; the best glucose conversion into polysaccharide was obtained from 3% of sucrose (81.8%), and the maximum production occurred about 35 hours after the end of the log phase of growth, in MRS sucrose broth. Polysaccharide formation did not occur above 40 degrees C, a temperature at which no growth was observed. The two variants were forming minicells by abnormal divisions.     

Lactobacilli isolated from sugary kefir grains capable of polysaccharide production and minicell formation

Homo- and heterofermentative species of Lactobacillus have been isolated from sugary kefir grains. Most of the homofermentative strains fermented tagatose and aldonitol and presented 48–54% of homology with Lactobacillus paracasei ssp. paracasei NCDO 151 (ex Lactobacillus casei ). The two variants of a heterofermentative species, although fermenting arabinose, were related to Lactobacillus hilgardii NCDO 264 (type strain) with 88% of homology. One of them produced polysaccharide from sucrose at pH 4–8 and 30°C; the best glucose conversion into polysaccharide was obtained from 3% of sucrose (81–8%), and the maximum production occurred about 35 hours after the end of the log phase of growth, in MRS sucrose broth. Polysaccharide formation did not occur above 40°C, a temperature at which no growth was observed. The two variants were forming minicells by abnormal divisions.     

Cloning and expression of the beta-galactosidase genes from Lactobacillus reuteri in Escherichia coli

Heterodimeric beta-galactosidase of Lactobacillus reuteri L103 is encoded by two overlapping genes, lacL and lacM. The lacL (1887bp) and lacM (960bp) genes encode polypeptides with calculated molecular masses of 73,620 and 35,682Da, respectively. The deduced amino acid sequences of lacL and lacM show significant identity with the sequences of beta-galactosidases from other lactobacilli and Escherichia coli. The coding regions of the lacLM genes were cloned and successfully overexpressed in E. coli using an expression system based on the T7 RNA polymerase promoter. Expression of lacL alone and coexpression of lacL and lacM as well as activity staining of both native and recombinant beta-galactosidases suggested a translational coupling between lacL and lacM, indicating that the formation of a functional beta-galactosidase requires both genes. Recombinant beta-galactosidase was purified to apparent homogeneity, characterized and compared with the native beta-galactosidase from L. reuteri L103.     

Lower plasma triglyceride level in Syrian hamsters fed on skim milk fermented with Lactobacillus casei strain Shirota

The effect of fermented skim milk (FSM) by Lactobacillus casei strain Shirota on plasma lipids in hamsters was examined. Hamsters fed on cholesterol-free and -enriched diets containing 30% FSM had lower levels of plasma triglyceride than those fed on the control diet. In the experiment with the cholesterol-enriched diet-fed hamsters, the plasma triglyceride level was suppressed by FSM at concentrations of 10% to 30%. Unfermented milk tended to lower the level of triglyceride, but not significantly. The plasma cholesterol concentration was not affected by an FSM and unfermented skim milk supplement to the diet. L. casei strain Shirota grew well in the presence of mixed lipid micelles containing bile acid, but did not have the ability to remove cholesterol from the culture broth. These results indicate that FSM lowered the plasma triglyceride level in hamsters.     

The effect of cell immobilization on the antibacterial activity of Lactobacillus reuteri DPC16 cells during passage through a simulated gastrointestinal tract system

Cell immobilization has the ability to influence the survival and functional characteristics of probiotic bacterial strains in harsh environments. This study investigated the effect of cell immobilization and passage through a simulated gastrointestinal tract (GI) on the antibacterial activity of Lactobacillus reuteri DPC16. Antibacterial activity, reuterin production and diol dehydratase activity were assayed in recovered isolates of L. reuteri that had been immobilized in Ca alginate-skim milk, and incubated in simulated GI fluids. Among all the recovered isolates tested, any that had undergone immobilization followed by immediate recovery of the cells without subsequent incubation in any fluids demonstrated the highest reuterin production, antimicrobial activity and diol dehydratase enzyme activity. L. reuteri DPC16 cells that had been immobilized, incubated in simulated GI fluids, and subsequently recovered from the beads often showed some loss of antimicrobial activity compared to the immobilized cells. The data confirm that the process of immobilization of L. reuteri in Ca alginate-skim milk, rather than the passage through simulated GI fluids, resulted in enhanced antibacterial activity. This is attributed to increased diol dehydratase activity, resulting in increased reuterin production.     

植物乳杆菌发酵、冻干工艺及其益生特性的研究

目的以Lactobacillus plantarum SQ-2506为目标,研究该菌株的发酵、冻干工艺及其益生特性。方法通过对培养基中C源、N源和刺激因子的浓度改变考察对活菌数的影响,从而确定培养基的最佳配方;在确定最佳培养基后做出该菌的生长曲线以确定最佳发酵时间点;同时考察冻干保护剂的配方和预冷时间对菌粉活菌数的影响;此外,对植物乳杆菌进行产酸、产H_2O_2、生物膜形成能力、抑菌特性以及抗氧化能力的检测。结果最佳MRS培养基中葡萄糖浓度为0.8%、酪蛋白胨为0.4%、牛肉粉为0.6%、吐温为0.06%;植物乳杆菌的生长曲线在5h时达到稳定期,此时发酵液活菌数为3.16×10~9 CFU/mL,发酵液的pH为4.45。最佳冻干保护剂的配方:脱脂乳100g/L,蔗糖120g/L,抗坏血酸20g/L,谷氨酸钠30g/L;冻干前对上机液预冻时间为2h,此时菌粉冻干存活率为70.21%。该菌株具有产酸、产H_2O_2能力,并对大肠埃希菌、金黄色葡萄球菌和白色假丝酵母均有一定的抑制作用,形成膜能力较强,且具有一定的抗氧化能力。结论通过培养基成分、发酵条件和冻干工艺的优化以及对其益生特性的研究,为下一步新药开发和规模化生产奠定基础。     

Probiotic properties of Lactobacillus strains isolated from the feces of breast-fed infants and Taiwanese pickled cabbage

This study assessed potential probiotic Lactobacillus strains isolated from the feces of breast-fed infants and from Taiwanese pickled cabbage for their possible use in probiotic fermented foods by evaluating their (i) in vitro adhesive ability, resistance to biotic stress, resistance to pathogenic bacteria, and production of β-galactosidase; (ii) milk technological properties; and (iii) in vivo adhesive ability, intestinal survival and microbial changes during and after treatment. Five Lactobacillus isolates identified as Lactobacillus reuteri F03, Lactobacillus paracasei F08, Lactobacillus rhamnosus F14, Lactobacillus plantarum C06, and Lactobacillus acidophilus C11 that showed resistance to gastric juice and bile salts were selected for further evaluation of their probiotic properties. All the strains demonstrated the ability to adhere to Caco-2 cells, particularly, strain L. plantarum C06 and L. reuteri F03 showed satisfactory abilities, which were similar to that of the reference strain L. rhamnosus GG. The strains L. paracasei F08 and L. acidophilus C11 had the highest β-galactosidase activity. Most of the strains were resistant to aminoglycosides and vancomycin but sensitive to ampicillin, erythromycin, and penicillin. All the 5 strains elicited antibacterial activity against both Gram-positive (Bacillus cereus, Listeria monocytogenes and Staphylococcus aureus) and -negative (Escherichia coli and Salmonella enterica) pathogens. Moreover, the strains L. reuteri F03, L. paracasei F08, and L. plantarum C06 could grow rapidly in milk without nutrient supplementation and reached 10? cfu/mL after 24 h of fermentation at 37 °C. The viable cell counts of the 3 strains remained above 10? cfu/mL after 21 d of storage at 4 °C. In the animal feeding trial, the number of intestinal lactobacilli increased significantly after administration of milk fermented with the 3 strains, and the counts of fecal coliforms and Clostridium perfringens were markedly reduced. Lactobacillus strains could also survive in the ileal intestinal tissue of the treated rats. Technologically interesting Lactobacillus isolates may be used in the future as probiotic starter cultures for manufacturing novel fermented foods.     

Chitosan oligosaccharides, dp 2-8, have prebiotic effect on the Bifidobacterium bifidium and Lactobacillus sp

In order to investigate the prebiotic potential of chitosan oligosaccharide (COS), prepared by enzymatic hydrolysis of fully deacetylated chitosan polymer, the effect of COS on bacterial growth was studied. The degree of polymerization (dp) of COS was determined by MALDI-ToF mass spectrometry, and the COS was found to be composed of dimer (33.6%), trimer (16.9%), tetramer (15.8%), pentamer (12.4%), hexamer (8.3%), heptamer (7.1%), and octamer (5.9%). The minimum inhibitory concentrations (MIC) of chitosan polymer against lactic acid bacteria and bifidobacteria were below 0.31%. However, this only applied to two strains, the other bacteria tested grew on MRS broth containing 5% COS. The effects of COS on the growth of bifidobacteria and lactic acid bacteria were compared with those of fructo-oligosaccharide (FOS). FOS was found to have a growth stimulatory effect on only three strains: Bifidobacterium bifidium, B. infantis and Lactobacillus casei. However, COS stimulated the growth of most Lactobacillus sp. and B. bifidium KCTC 3440. The amount of the growth and the specific growth rate of B. bifidium increased with increasing COS concentration. The cultivation time required to obtain maximum growth was reduced to about 25% in MRS broth supplemented with 0.2-0.4% COS. These results demonstrate that COS has considerable bifidogenic potential. Both cell growth and specific growth rates of L. brevis in MRS broth supplemented with 0.1% COS increased by 25%. The present study shows that COS stimulates the growth of some enteric bacteria, and that COS has potential use as a prebiotic health-food.     

Human-derived probiotic Lactobacillus reuteri demonstrate antimicrobial activities targeting diverse enteric bacterial pathogens

Lactobacillus reuteri is a commensal-derived anaerobic probiotic that resides in the human gastrointestinal tract. L. reuteri converts glycerol into a potent broad-spectrum antimicrobial compound, reuterin, which inhibits the growth of gram-positive and gram-negative bacteria. In this study, we compared four human-derived L. reuteri isolates (ATCC 55730, ATCC PTA 6475, ATCC PTA 4659 and ATCC PTA 5289) in their ability to produce reuterin and to inhibit the growth of different enteric pathogens in vitro. Reuterin was produced by each of the four L. reuteri strains and assessed for biological activity. The minimum inhibitory concentration (MIC) of reuterin derived from each strain was determined for the following enteric pathogens: enterohemorrhagic Escherichia coli, enterotoxigenic E. coli, Salmonella enterica, Shigella sonnei and Vibrio cholerae. We also analyzed the relative abilities of L. reuteri to inhibit enteric pathogens in a pathogen overlay assay. The magnitude of reuterin production did not directly correlate with the relative ability of L. reuteri to suppress the proliferation of enteric pathogens. Additional antimicrobial factors may be produced by L. reuteri, and multiple factors may act synergistically with reuterin to inhibit enteric pathogens.     

Supplementation with Lactobacillus reuteri or L. acidophilus reduced intestinal shedding of cryptosporidium parvum oocysts in immunodeficient C57BL/6 mice.

The effect of L. acidophilus supplementation to reduce fecal shedding of Cryptosporidium parvum oocysts was compared to L. reuteri using C57BL/6 female mice immunosuppressed by murine leukemia virus (strain LP-BM5) inoculation. After 12 weeks post LP-BM5 inoculation, 15 immunosuppressed mice each were randomly assinged to one of the following treatment groups: historical control (group A), LP-BM5 control (group B), C. parvum (group C), L. reuteri plus C. parvum (group D) or L. acidophilus plus C. parvum (group E). Mice were pre-fed the L. reuteri or L. acidophilus bacteria strains daily for 13 days, challenged with C. parvum oocysts and thereafter fed the specified Lactobacillus regimens daily during the experimental period. Animals supplemented with L. reuteri shed fewer (p<0.05) oocysts on day-7 post C. parvum challenge compared to controls. Mice supplemented with L. acidophilus also shed fewer (p<0.05) oocysts on days 7 and 14 post-challenge compared to controls. Overall, Lactobacillus supplementation reduced C. parvum shedding in the feces but failed to suppress the production of T-helper type 2 cytokines [interleukin-4 (IL-4), IL-8)] which are associated with immunosuppression. Additionally, Lactobacillus supplementation did not restore T-helper type 1 cytokines (interleukin-2 (IL-2) and gamma interferon (IFN-gamma), which are required for recovery from parasitic infections. Altered T-helper types 1 and 2 cytokine production as a consequence of immunodysfunction permitted the development of persistent cryptosporidiosis while mice with intact immune system were refractory to infection with C. parvum. Reduction in shedding of oocysts observed in the Lactobacillus supplemented mice during deminished IL-2 and IFN-gamma production may be mediated by factors released into the intestinal lumen by the Lactobacillus and possibly other host cellular mechanisms. These observations suggest that L. reuteri or L. acidophilus can reduce C. parvum parasite burdens in the intestinal epithelium during cryptosporidiosis and may serve potential benefits as probiotics for host resistance to intestinal parasitic infections. L. acidophilus was more efficacious in reducing fecal shedding than L. reuteri and therefore may also have implication in the therapy of cryptosporidiosis during immunosuppressive states including human AIDS.     

Conjugated linoleic acid conversion by dairy bacteria cultured in MRS broth and buffalo milk

AIMS: To evaluate strains of Lactobacilli, Bifidobacteria and Streptococci for their ability to produce conjugated linoleic acid (CLA) from free linoleic acid (LA). METHODS AND RESULTS: Eight dairy bacteria tolerant to LA were grown in MRS broth containing LA (200 microg ml(-1)) and CLA was assessed. Seven bacteria were able to form CLA after 24 h of incubation, varying percentage conversion between 17% and 36%. Lactobacillus casei, Lactobacillus rhamnosus, Bifidobacterium bifidum and Streptococcus thermophilus showed the highest LA conversion and were inoculated into buffalo milk supplemented with different concentration of LA. The production of CLA at 200 microg ml(-1) of LA was two- or threefold in milk than MRS broth. All evaluated strains were able to produce CLA from high LA levels (1000 microg ml(-1)). CONCLUSIONS: The most tolerant strain to LA was Lact. casei. Lacttobacillus rhamnosus produced the maximum level of CLA at high LA concentrations (800 microg ml(-1)). The selected bacteria may be considered as adjunct cultures to be included on dairy fermented products manufacture. Low concentration of LA must be added to the medium to enhance CLA formation. SIGNIFICANCE AND IMPACT OF THE STUDY: The production of CLA by strains using milks from regional farms as medium offer a possible mechanism to enhance this beneficial compound in dairy products and those the possibility to develop functional foods.     

Identification and physiological characteristics of heterofermentative strains of Lactobacillus from South African red wines

Nineteen atypical heterofermentative strains of Lactobacillus spp. isolated from South African red wines were identified with the API 50 CHL system and by computerized comparison of their total soluble cell protein patterns. Eleven strains were identified as Lactobacillus hilgardii and eight strains as L. brevis . Three strains of L. hilgardii and three strains of L. brevis produced small amounts of H₂S in peptone water supplemented with 001% l -cysteine. All strains produced mannitol from fructose. Proteolytic activity was detected in all except two strains of L. hilgardii . Strains capable of digesting gelatine, hydrolized casein, but not vice versa . The excessive production of sulphur-containing compounds, mannitol and acetaldehyde by lactic acid bacteria could have serious quality implications for the wine industry. Three strains of L. hilgardii and all strains of L. brevis decarboxylated l -malic acid to l -lactic acid.     

Cytotoxic activity of lactobacilli isolated from plant and dairy sources

Forty four cultures of Lactobacilli isolated from their natural sources such as dahi, raw milk and fermenting rice-pulse doughs etc. along with four standard strains of Lactobacilli were assayed for their cytotoxic activity against three secondary tumour cell lines. Three cultures isolated from dahi samples and identified as Lactobacillus casei D-34, L. casei D-48a, L. plantarum D-70a along with one standard strain L. casei B 1922 exhibited significant cytotoxic activity in the range of 30 to 36%.