Screening Of Lactic Acid Bacteria Research Articles

Screening of lactic acid bacteria for their potential as microbial cell factories for bioconversion of lignocellulosic feedstocks.

BackgroundThe use of fossil carbon sources for fuels and petrochemicals has serious impacts on our environment and is unable to meet the demand in the future. A promising and sustainable alternative is to substitute fossil carbon sources with microbial cell factories converting lignocellulosic biomass into desirable value added products. However, such bioprocesses require availability of suitable and efficient microbial biocatalysts, capable of utilizing C5 sugars and tolerant to inhibitory compounds generated during pretreatment of biomass. In this study, the performance of a collection of lactic acid bacteria was evaluated regarding their properties with respect to the conversion of lignocellulosic feedstocks. The strains were examined for their ability to utilize xylose and arabinose as well as their resistance towards common inhibitors from pretreated lignocellulosic biomass (furan derivatives, phenolic compounds, weak acids).ResultsAmong 296 tested Lactobacillus and Pediococcus strains, 3 L. pentosus, 1 P. acidilactici and 1 P. pentosaceus isolates were found to be both capable of utilizing xylose and arabinose and highly resistant to the key inhibitors from chemically pretreated lignocellulosic biomass. When tested in broth with commonly found combinations of inhibitors, the selected strains showed merely 4%, 1% and 37% drop in growth rates for sugarcane bagasse, wheat straw and soft wood representatives, respectively, as compared to Escherichia coli MG1655 showing decreased growth rates by 36%, 21% and 90%, respectively, under the same conditions.ConclusionThe study showed that some strains of Lactobacilli and Pediococci have the potential to be used as production platforms for value-added products from pretreated lignocellulosic biomass. Selected Lactobacilli and Pediococci strains were able to tolerate the key inhibitors in higher concentrations compared to E.coli; in addition, as these isolates were also capable of fermenting xylose and arabinose, they constitute good candidates for efficient lignocellulosic feedstock bioconversions.

Rapid detection assay for oxygen consumption in the Lactobacillus casei group

A rapid method based on the time of resazurin reduction was optimized and use to evaluate the oxygen consumption in Lactobacillus casei, L. paracasei and L. rhamnosus strains grown under anaerobic, aerobic and respiratory promoting conditions. A good correlation was found between the resazurin assay and polarographic measurements. The new method proved to be a faithful indicator of oxygen uptake as well as fast and effective for testing a large number of strains. Additionally, being correlated to other markers of aerobic and respiratory phenotypes (improved growth and activity of enzymes related to oxygen metabolism), the resazurin assay may greatly facilitate the screening of lactic acid bacteria for the ability to use oxygen under different growth conditions and the selection of potentially respiration-competent strains.

Screening of Lactic Acid Bacteria for Antifungal Activity against Fungi

Many chemical preservatives that target fungi growth in food have been approved and used for many years. Recently the consumers are looking and demanding for products without chemical preservatives and still maintain good shelf life and safe. The growth of spoilage fungi have been a global concern because of the economy loses and the health hazard of the mycotoxins produced by the spoilage fungi. A total of 22 lactic acid bacteria isolated from Tarhana and Lactic acid bacteria were screened for antifungal activity using dual agar overlay method and well method against Alternaria alternata, Aspergillus parasiticus, Aspergillus oryzae Penicillium griseofulvum, Penicillium chrysogenum, Penicillium notatu, Penicillium citrinum, Penicillium roquefort, Aspergillus fumigatus. Ten isolates showed inhibition activity after 72 h incubation at 30°C. Supernatant of 10 isolates with strong antifungal activity was evaluated by well method and they inhibited the growth of the fungi at 30°C for 72 h. F2,1 supernatant reduced the mass growth of Penicillium griseofulvum, Penicillium chrysogenum Aspergillus fumigatus and Aspergillus parasiticus when incubated for 6 days at 30°C. The isolates were identified using rapid ID 32 Strep as Enterococcus durans F2.1. F2.1 isolates studied inhibited the growth of the mycelia and conidia germination of the fungi which indicate the possibility of using LAB isolates as biopreservative.

Lactobacillus plantarumCECT 7527, 7528 and 7529: probiotic candidates to reduce cholesterol levels

Hypercholesterolaemia plays a key role in the development and progression of coronary artery disease. There are numerous drugs available to treat this condition but they are often expensive and can have unwanted side effects. Therefore, a screening of lactic acid bacteria to select candidate probiotic strains to reduce cholesterol levels was carried out. Three Lactobacillus plantarum strains (CECT 7527, 7528 and 7529) were selected as potential probiotics to reduce cholesterol levels after conducting several in vitro tests for demonstrating the functionalities of the strains according to international guidelines. The three strains showed a high ability to survive under gastrointestinal tract conditions and to adhere to intestinal cells. Regarding lipid metabolism, the strains showed a great production of bile salt hydrolase, especially when combined. Moreover, the strains assimilated cholesterol directly from the medium. Part of the cholesterol present in the medium was removed via binding onto the bacterial cellular surface. Finally, the three strains, especially CECT 7529, produce large quantities of propionic and butyric acids. Combined, these characteristics suggest that these strains could be excellent candidates for reducing high blood cholesterol levels.

Antimicrobial Properties and Lactase Activities from Selected Probiotic Lactobacillus brevis Associated With Green Cacao Fermentation in West Sumatra, Indonesia

Lactase activity is very important enzyme for Lactose Intolerant people. The lactic acid bacteria selected for use as Probiotic bacteria should be able to tolerate many organotoxic or heavy metal toxicities in intestine at least for 90 minute, attach to the epithelium, and grow in the lower intestinal tract before they can start providing any health benefits. The Green varieties of cacao fruits were used for cacao bean fermentation. The cacao bean covers with white pulp containing fructose, e.g. 42 mg/g, glucose 24 mg/g and sucrose 21 mg/g, as carbon source of Lactic Acid Bacteria (LAB). Screening of LAB was carried out after 24-36 h during spontaneous fermentation. This paper aims to find potential LAB resistant acid pH and producing potential antimicrobial and showing high protease/lactase activities. The medium of de Man, Ragosa, and Sharpe (MRS) were used to screen LAB, and 63 colonies were found. The screening of isolates is based on LAB survival growth in acid pH ranges (2.0; 2.5 and 3.0) and body temperature (37°C). For Antimicrobial experiments were used pathogen bacterial E. coli and Salmonela (Unand Collection) as indicator strain. Six isolate were conformed as strong antimicrobial and selected as potential for producing protease (lactase) using specific Triple Sugar Iron Agar (TSIA) medium. The isolate G3 and G6 were selected for further enzyme protease delivered with 2% Skim Milk as a protein subsrate. The results showed, the maximum amount of protease activity potential from isolate G6 in acid pH (3.0) were calculated as 0.0088 and protease activity 1.1795 Unit/mL, while the optimum of protease activity was found at pH (6.0) calculated protease activity 3.150 Unit/mL. This study could explain the possibility of using potential isolate G6 LAB as Probiotic for dairy or food Industry and supplement tablet. There is no report so far concerning this topic and potential isolate G6, with high antimicrobial or wide pH of protease. The study will continue to purify antimicrobial Bacteriocin and amino acid structure determination. The G6 isolate was 95% polymorphism with Lactobacillus brevis.

Screening of lactic acid bacteria isolated from fermented table olives with probiotic potential

The aim of this work was to study the potential probiotic properties of lactobacilli associated with table olives. From a total of 111 isolates from spontaneously fermented green olive brines, 109 were identified at species level by multiplex PCR amplifications of the recA gene. One hundred and seven of these were identified as Lactobacillus pentosus, one as Lactobacillus plantarum, and another as Lactobacillus paraplantarum. Repetitive bacterial DNA element fingerprinting (rep-PCR) with GTG5 primer revealed a higher variability within the L. pentosus isolates and nine different clusters were obtained. Most of them showed high autoaggregation ability, low hydrophobicity properties, and lower survival to gastric than to pancreatic digestion; however, no isolate showed bacteriocin, haemolytic or bile salt hydrolase activities. A multivariate analysis based on results from phenotypic tests led to the segregation of some L. pentosus isolates with promising potential probiotic characteristics, which are even better than probiotic reference strains. Due to the autochthonous origin of the strains, their use as starter cultures may contribute to improving natural fermentation and the nutritional characteristics of table olives.

Screening of lactic acid bacteria for reducing power using a tetrazolium salt reduction method on milk agar

Reducing activity is a physiological property of lactic acid bacteria (LAB) of technological importance. We developed a solid medium with tetrazolium dyes enabling weakly and strongly reducing LAB to be discriminated. It was used to quantify populations in a mixed culture (spreading method) and screen strains (spot method).

An alternative method for screening lactic acid bacteria for the production of exopolysaccharides with rapid confirmation

The accumulation of exopolysaccharides (EPS) produced by microorganisms occurs in the presence of excess substrate and limiting conditions of elements that are essential to growth, such as nitrogen, phosphorus, sulfur, and magnesium. The presence of EPS produced by bacterial cells contributes to slime colonies formation in solid medium and increased viscosity in liquid medium. This paper proposes an alternative method for screening EPS-producing lactic acid bacteria using solid medium-containing discs of filter paper that are saturated with active cultures. The screening was carried out under different culture conditions varying the type of sugar, pH, and temperature. EPS production was visualized by the presence of mucoid colonies on the discs, which was confirmed by the formation of a precipitate when part of this colony was mixed with absolute alcohol. The established conditions for obtaining a high number of isolates producing EPS were 10% sucrose, pH 7.5 and 28 ºC. This method proved to be effective and economical because several strains could be tested on the same plate, with immediate confirmation.

Screening of lactic acid bacteria for fermentation of minced wastes of Argentinean hake (Merluccius hubbsi)

Sixteen strains of lactic acid bacteria were evaluated for their capacity of acidification of Merluccius hubbsi fish wastes obtained from a processing factory. Only three lactobacilli (Lactobacillus buchneri B-1837, Lactobacillus arizonensis B-14768 and Lactobacillus plantarum B-4496) were able to reduce the pH value to 4.0 or below when using glucose or sucrose as carbon source. Either with only 25gl−1 of glucose or sucrose, L. arizonensis B-14768 reduced the pH to 3.8±0.2 within 24h of fermentation. The acid tolerance test (pH 3.0 at 37°C) for the strains presented DpH3-values of 192, 383 and 767min for L. buchneri, L. plantarum and L. arizonensis, respectively. However, at a lower pH value (pH 2.0) only L. arizonensis was significantly recovered after 45min of exposure (DpH2 68min). Considering together the acidification capacity, the tolerance to other stresses (heat and bile salts) and the lower optimum temperature for the process, L. arizonensis is described as a suitable strain for M. hubbsi silage; constituting a promissory alternative for fish fermentation at location with temperate or cold climes.

Isolation and Screening of Lactic Acid Bacteria from the Gut of Blue Swimming Crab, P. pelagicus, an in vitro Inhibition Assay and Small Scale in vivo Model for Validation of Isolates as Probiotics

Isolation and Screening of Lactic Acid Bacteria from the Gut of Blue Swimming Crab, P. pelagicus, an in vitro Inhibition Assay and Small Scale in vivo Model for Validation of Isolates as Probiotics

Isolation and applied potential of lactic acid bacteria from Chinese traditional fermented food in specific ecological localities

The isolation and screening of lactic acid bacteria (LAB) from natural sources have been one of the powerful means to obtain strains for the food industry. A total of 275 indigenous isolates were obtained from 43 samples of traditional fermented foods in specific ecological niches throughout the northwestern China, and among which 13 strains of LAB were selected for their potential in food preservation and production. Among the 13 isolates, Lactobacillus (10) was dominant over Lactococcus (3). The distribution of the isolates was as follows: Lactobacillus paracasei ssp. paracasei (J23, M10, M20, M22), Lactobacillus rhamnosus (J20, M18), Lactococcus lactis ssp. lactis (X20, Q7), Lactobacillus casei (Q1, Q12), Lactobacillus plantarum (J11), Lactococcus lactis ssp. cremoris (X8), Lactobacillus delbrueckii ssp. bulgaricus (Q5). All 13 isolates produced bacteriocin with a broad inhibitory spectrum against selected Gram-positive as well as Gram-negative pathogenic and spoilage species. Biochemical analysis revealed that they possessed high acidification and coagulation activity. Several strains possessed the high activity of 2 or 3 technological characteristics, related to novel starters and food preservatives.

Isolation and characterization of probiotic strains for improving oral health

Probiotics have been proven effective for preventing caries. In contrast, the effect of probiotics on improving oral diseases such as gingivitis, periodontitis and halitosis has been less explored. ObjectiveTo perform a screening of lactic acid bacteria, according to international guidelines for the evaluation of probiotics, in order to select candidate probiotic strains for preventing oral disorders. Study designThe strains were isolated from healthy children and were subjected to a variety of in vitro tests in order to show their functionality. The safety of the strains was assessed by determining antibiotic susceptibility and production of lactic acid. ResultsForty-six of the 100 new isolates were assigned to lactic acid bacteria genera after a biochemical characterization. Most of the new isolated strains seem to be resistant to oral conditions, have great ability to form aggregates and have high antagonistic activity against oral pathogens. None of the strains produced unpleasant volatile compounds. The strains showed high ability to adhere to oral tissues and they do not present any antibiotic resistance. Moreover, an increased risk of developing caries due to their ability to produce lactic acid was discarded in seven pre-selected probiotic candidates. ConclusionsThese lactic acid bacteria show promising properties to be used as potential probiotics for improving oral health.

Inhibitory effects of enterococci on the production of hydrogen sulfide by hydrogen sulfide-producing bacteria in raw meat

Applying competitive exclusion micro-organisms to control hydrogen sulfide (H₂S) gas produced by hydrogen sulfide-producing bacteria (SPB) in chicken meat. Five SPB strains, isolated from animal by-products, were used for screening lactic acid bacteria (LAB) that can inhibit the production of H₂S by SPB in trypticase soy broth supplemented with L-cysteine (TSB-L-cys). A sensitive and accurate test strip method was developed for H₂S determination in real time. One LAB strain, isolate L86, from cheese whey, demonstrated the highest inhibitory activity against the production of H₂S by SPB. The isolate L86 was confirmed as Enterococcus faecium that does not possess genes encoding for vancomycin resistance based on PCR analysis. Enterococcus faecium strain L86 reduced (P < 0·05) the yield of H₂S upto 51·2% in 10 h at 35°C in TSB-L-cys medium. In fresh chicken meat, the yield of H₂S produced by the artificially inoculated SPB was reduced (P < 0·05) by 48·6, 49·7 and 69·8% in 10 h at 35, 30 and 25°C, respectively. Enterococcus faecium strain L86 also reduced (P < 0·05) by 53·8% on the yield of H₂S produced by the indigenous SPB in partially spoiled chicken meat at 35°C for 10 h. Enterococcus faecium strain L86 is effective on inhibiting the production of H₂S by SPB. The application of this biological agent to raw animal by-products will provide a safer working environment in rendering processing plants and produce higher-quality rendered products.

Screening of Lactic Acid Bacteria for Antifungal Activity against &lt;i&gt;Aspergillus oryzae&lt;/i&gt;

Problem statement: The growth of spoilage fungi have been a global concern because of the economy loses and the health hazard of the mycotoxins produced by the spoilage fungi. Approach: A total of 137 lactic acid bacteria isolated from Malaysian fruits and fermented foods were screened for antifungal activity using dual agar overlay method and well method against A. oryzae. Results: 23 isolates showed inhibition activity after 72 h incubation at 30°C. Supernatant of three isolates with strong antifungal activity was evaluated by well method and they inhibited the growth of the fungi at 30°C for 72 h. LAB supernatant reduced the mass growth of Aspergillus oryzae when incubated for 7 days at 30°C. The isolates were identified using API 50CH as Lactobacillus brevis G004, Lactobacillus fermentum Te007 and Pediococcus pentosaceus Te010. Conclusion: The three isolates studied inhibited the growth of the mycelia and conidia germination of the fungi which indicate the possibility of using LAB isolates as biopreservative.

Production of bacteriocin-like substances by lactic acid bacteria isolated from regional ovine cheese

Lactic acid bacteria (LAB) were isolated from ovine milk and cheeses manufactured in the South Region of Brazil. Among 112 bacterial isolates investigated, 59 were chosen through a screening for LAB. Among these 59 strains of LAB, 21% showed antimicrobial, proteolytic and lipolytic activities. Based on this screening, Lactobacillus plantarum LCN 17 and Lactobacillus rhamnosus LCN 43 were selected and tested for the production of bacteriocin-like substances (BLS). The BLS produced by both isolates showed antimicrobial activity against Listeria monocytogenes, whereas that produced by L. plantarum LCN 17 presented higher stability to different temperature, pH and enzyme treatments. These strains present potential for production of BLS, and for use as starter cultures.

Isolation and screening of lactic acid bacteria from Thai traditional fermented fish ( Plasom) and production of Plasom from selected strains

Lactic acid bacteria (LAB) were isolated from traditional Thai fermented fish, Plasom at various fermentation periods. It was found that 138 isolates exhibited a clear zone and growth on MRS agar supplemented with CaCO 3; however, only 133 isolates were identified as LAB. Only 14 strains showed excellent inhibition zone diameters on agar when Salmonella sp. was used as an indicator for preliminary detection of antagonistic activity. Staphylococcus aureus was used for secondary screening for antagonistic activity of these 14 strains. It was found that only 7 strains exhibited good inhibition zone diameters on agar, and all of them could inhibit E. coli as the third indicator. The strains which exhibited widest zones of inhibition against Escherichia coli, S. aureus and Salmonella sp. were LPS04, LPS17, and LD219 and LPS18 respectively. Tested pathogenic strains were inhibited by 4 selected LAB. The strain which showed the best lactic acid production and pH reduction ability was LD219. Using 16s rDNA sequence analysis, LD219 was identified as Streptococcus salivarius, LPS04, LPS17 and LPS18 were identified as Enterococcus faecalis. Plasom was produced by using a mixed culture (LD219, LPS04, LPS17 and LPS18) as a starter culture compared with spontaneous and back-slopping processes. Significant differences ( p < 0.05) in pH, its titratable acidity as lactic acid and number of total viable counts (TVC), LAB and Enterobacteriaceae were found in these Plasom at 0 and 8 days. However, no significant difference ( p > 0.05) was observed in terms of colour, smell, taste, sour, texture and overall acceptance of Plasom produced by non-starter cultured, back-slopping and starter cultured processes.

Screening lactic acid bacteria from swine origins for multistrain probiotics based on in vitro functional properties

Lactic acid bacteria originated from swine feces and intestines were selected for potential probiotics based on their bile-salt resistance, low pH tolerance, potential adhesion to epithelial cells and especially functional properties, including production of antimicrobial substances, bile-salt hydrolase (BSH) and amylolytic activity. Results showed 7 isolates with antimicrobial activity, 5 with BSH activity and 3 with amylolytic activity were preliminarily selected from 485 lactic acid bacteria based on their highest potential with functional properties in vitro. The 15 isolates were further assayed on the essential characteristics as potential probiotics. All isolates were fully tolerant to 0.3% bile salts and 11 of them were able to resist pH 3 for 3 h without loss of viable cells. The eleven isolates were then evaluated on their adhesion capability. Wide variation in the hydrophobic character and specific adhesion efficiency was observed and three isolates G1-1, G22-2 and G8-5, with respective antimicrobial, BSH and amylolytic activities were finally selected. In addition, the three isolates were compatible in the coexistence assay. Isolate G1-1 was identified as Lactobacillus salivarius by API system and a 16S rRNA gene sequence analysis. Both G8-5 and G22-2 showed the closest homology to Lactobacillus reuteri according to their 16S rRNA gene sequences (99%). From the study, the three Lactobacilli strains were shown to share the functional properties necessary for probiotics use in animal additives. Their compatibility with respective in vitro activities was expected to show enhanced in vivo efficacy after combination for multistrain probiotics use.

Production of bacteriocin-like substances by lactic acid bacteria isolated from regional ovine cheese.

Lactic acid bacteria (LAB) were isolated from ovine milk and cheeses manufactured in the South Region of Brazil. Among 112 bacterial isolates investigated, 59 were chosen through a screening for LAB. Among these 59 strains of LAB, 21% showed antimicrobial, proteolytic and lipolytic activities. Based on this screening, Lactobacillus plantarum LCN 17 and Lactobacillus rhamnosus LCN 43 were selected and tested for the production of bacteriocin-like substances (BLS). The BLS produced by both isolates showed antimicrobial activity against Listeria monocytogenes, whereas that produced by L. plantarum LCN 17 presented higher stability to different temperature, pH and enzyme treatments. These strains present potential for production of BLS, and for use as starter cultures.

Screening of lactic acid bacteria from Indonesia reveals glucansucrase and fructansucrase genes in two differentWeissella confusastrains from soya

Homopolysaccharide (glucan and fructan) synthesis from sucrose by sucrase enzymes in lactic acid bacteria (LAB) has been well studied in the genera Leuconostoc, Streptococcus and Lactobacillus. This study aimed to identify and characterize genes encoding glucansucrase/glucosyltransferase (GTF) and fructansucrases/fructosyltransferase (FTF) enzymes from genomic DNA of 'rare' Indonesian exopolysaccharide-producing LAB. From a total of 63 exopolysaccharide-producing LAB isolates obtained from foods, beverages and environmental samples, 18 isolates showing the most slimy and mucoid colony morphologies on sucrose were chosen for further study. By comparing bacterial growth on De Man, Rogosa and Sharpe (MRS)-sucrose with that on MRS-raffinose, and using the results of a previous PCR screening study with degenerate primer pairs targeting the conserved catalytic domain of GTFs, various strains were identified as producers of fructan (13), of glucan only (five) or as potential producers of both glucan and fructan (nine). Here, we report the characteristics of three gtf genes and one ftf gene obtained from Weissella confusa strains MBF8-1 and MBF8-2. Strain MBF8-1 harbored two putative gtf genes with high sequence similarity to GTFB of Lactobacillus reuteri 121 and GTF180 of L. reuteri 180, respectively. Strain MBF8-2 possessed single gtf and ftf genes with high sequence similarity to GTFKg3 of Lactobacillus fermentum Kg3 and DSRWC of Weissella cibaria, and FTF levansucrase of L. reuteri 121, respectively.

Screening of lactic acid bacteria toward their selection as a source of chicken probiotic

In this study, 332 lactic acid bacteria of broiler gut origin were investigated as putative probiotic candidates. Sixty-two bacteria showed the highest aggregation while showing antibacterial effects against Salmonella Enteritidis, Salmonella Typhimurium, and Escherichia coli O78:K80. Enzymatic activities of the selected bacteria were examined. No lipase activity was detected, but all of them showed almost similar proteolytic activities. However, they had different amylase and phytase activities. Four of the 62 bacterial strains were selected as a result of aggregation and amylase tests. They were chosen for the following attributes: high cell surface hydrophobicity, co-aggregation, and resistance to bile salts and also acidic conditions. Finally, Lactobacillus crispatus was selected as a source of potential probiotic because of its predominant characteristics in comparison to the other isolated strains from the gastrointestinal tract of chickens. This study has provided a good arrangement of rapid methods for screening a high number of bacteria: a series of beneficial tests that are used together for the first time on chickens, and not any other animals.