Carbohydrate Fermentation Profiles Research Articles

Development of two devices for high-throughput screening of ethanol-producing microorganisms by real-time CO2 production monitoring.

Bioethanol's importance as a renewable energy carrier led to the development of new devices for the high-throughput screening (HTS) of ethanol-producing microorganisms, monitoring ethanol production, and process optimization. This study developed two devices based on measuring CO2 evolution (an equimolar byproduct of microbial ethanol fermentation) to allow for a fast and robust HTS of ethanol-producing microorganisms for industrial purposes. First, a pH-based system for identifying ethanol producers (Ethanol-HTS) was established in a 96-well plate format where CO2 emission is captured by a 3D-printed silicone lid and transferred from the fermentation well to a reagent containing bromothymol blue as a pH indicator. Second, a self-made CO2 flow meter (CFM) was developed as a lab-scale tool for real-time quantification of ethanol production. This CFM contains four chambers to simultaneously apply different fermentation treatments while LCD and serial ports allow fast and easy data transfer. Applying ethanol-HTS with various yeast concentrations and yeast strains displayed different colors, from dark blue to dark and light green, based on the amount of carbonic acid formed. The results of the CFM device revealed a fermentation profile. The curve of CO2 production flow among six replications showed the same pattern in all batches. The comparison of final ethanol concentrations calculated based on CO2 flow by the CFM device with the GC analysis showed 3% difference which is not significant. Data validation of both devices demonstrated their applicability for screening novel bioethanol-producer strains, determining carbohydrate fermentation profiles, and monitoring ethanol production in real time.

Development of fermented wheat flour using indigenous yeast lactic starter consortium

This study aimed to develop fermented wheat flour (FWF) using native yeast lactic starter consortium isolated from dahi, a popular Indian fermented dairy product. Yeast and Lactic Acid Bacteria (LAB) were isolated from samples of local household dahi to assess their milk fermentation potential. Molecular methods were used to identify the LAB isolates, while yeast isolates were identified using a carbohydrate fermentation profile. Dahi samples were prepared with LAB isolate Lactiplantibacillus pentosus, and yeast isolate Candida spherica, and their combination showed superior sensory scores. The FWF was prepared using LAB, yeast and their combination, and sensory evaluation of FWF-based soup was performed. The FWF prepared had lower moisture (6%), carbohydrate (71.14%) and calorific value (345.4 kcal) content compared to commercially available wheat flour/atta. Microbiological analysis showed the absence of coliforms, E. coli and Staphylococcus aureus, indicating hygienic preparation and inhibition of spoilage and pathogenic bacteria. The low moisture content and acidic pH (4.4) of the FWF contributed to its storage stability. In conclusion, fermented wheat flour produced using native LAB from dahi is a costeffective, storage-stable functional food with live beneficial microorganisms, suitable for promoting gut health.

Isolation and identification of psychrotrophic lactic acid bacteria in godo, the traditional fermented soy food in Japan.

Godo is a traditional fermented soy food made in Aomori prefecture, Japan. It is mainly made of soybeans, rice koji, and salt. Since godo ripens during the long and severe winter in northeast Japan, it is assumed that lactic acid bacteria inhabiting godo have cold tolerance. We aimed to investigate the presence or absence of psychrotrophic lactic acid bacteria in godo. The viable counts of estimated lactic acid bacteria ranged from 106 to 108 cfu/g. In addition, aerobic and anaerobic microorganisms were detected in four godo products though the microbial population differed from sample to sample. Twenty-two bacterial strains were able to be isolated from godo, and all of the isolated strains were Gram-positive and catalase-negative. Some of the isolates grew well at 10°C. The carbohydrate fermentation profile of the selected three strains was determined by API50 CHL analysis. These strains were identified as Leuconostoc mesenteroides, and Latilactobacillus sakei by 16S rRNA gene sequence analysis. Leuconostoc mesenteroides strains HIT231 and HIT252, and Latilactobacillus sakei strain HIT273 could grow at 5°C in MRS broth, but their optimum growth temperature was 20°C-30°C. These results suggest that psychrotrophic lactic acid bacteria presumed to be derived from rice koji are present in godo, which is one of the factors in the low temperature ripening of godo in winter.

Genomic characterization and probiotic potential of Lactobacillus casei IDCC 3451 isolated from infant faeces.

Probiotics play an important role in health benefits on the host. However, they also possess potentials for infectivity or in situ toxin production; thus, requiring a comprehensive assessment of their safety. In this study, we report genomic characteristics of a newly isolated Lactobacillus casei IDCC 3451 from infant faeces. Phenotypic assays based on enzyme activities and carbohydrate fermentation profiles represented metabolic features of the strain. Safety evaluation for antimicrobial resistance, biogenic amines production and cytotoxicity to a murine mouse model suggested its safe use as a probiotic strain. Our findings on the genetic background of L. casei IDCC 3451 and its potential features provide a promising functional and safe probiotic strain for the human consumption.

Breath methane to hydrogen ratio as a surrogate marker of intestinal dysbiosis in head and neck cancer

Exhaled breath compounds can non-invasively detect head and neck squamous cell carcinoma (HNSCC). Here we investigated exhaled compounds related to intestinal bacterial carbohydrate fermentation. Fasting breath samples were collected into 3 litre FlexFoil PLUS bags from patients awaiting a biopsy procedure for suspected HNSCC. Samples were analysed using a Syft selected ion flow-tube mass spectrometer and a Quintron BreathTracker. Two tailed non-parametric significance testing was conducted with corrections for multiple imputations. 74 patients were diagnosed (histological) with HNSCC and 61 patients were benign (controls). The methane to hydrogen ratio was significantly different between cancer and non-cancer controls (p = 0.0440). This ratio increased with tumour stage with a significant difference between T1 and T4 tumours (p = 0.0259). Hydrogen levels were significantly higher in controls who were smokers (p = 0.0129), with no smoking dependent methane changes. There were no differences in short chain fatty acids between groups. Exhaled compounds of intestinal carbohydrate fermentation can detect HNSCC patients. These findings suggest a modified carbohydrate fermentation profile in HNSCC patients that is tumour stage and smoking status dependent.

Effect of the incorporation of β-galactosidase in the GOS production during manufacture of soft cheese

Galactooligosaccharides (GOS) are non-digestible oligosaccharides with recognized prebiotic role. The present study aims to evaluate a β-galactosidase from K. lactis during soft cheese making and to analyse the impact on carbohydrates metabolism, proteolysis, and volatile compounds production, physicochemical and microbiological characteristics of the product. The enzyme was added to cheese milk (fluid milk plus whey powder) before (40 min.) or simultaneously of the starter addition (Ep and E treatments, respectively); cheese without enzyme addition was also made (C treatment). Also, we characterized fresh and soft commercial cheeses from the point of view of carbohydrate fraction, highlighting GOS, and organic acid profiles.The inclusion of the enzyme in soft cheese making produced a delay in reaching the target pH (~5.2). Carbohydrate fermentation profiles differed among treatments during cheese making and ripening. GOS were only detected in Ep and E cheeses (0.88 and 0.51 g/100 g, respectively). Lactose content was lower, and glucose and galactose levels were higher in E and Ep than C. No differences in physicochemical and microbial composition and organic acids profiles among samples were observed. Bioformation of volatile compounds belonging to the chemical families of aldehydes, ketones, alcohols, esters and acids, was not substantially affected by the modification in the carbohydrate profile. GOS were not detected in any of the commercial cheeses; great variations in the carbohydrate contents and organic acids were found. The results obtained demonstrate the feasibility of obtaining cheeses with GOS. Although the GOS values achieved are not adequate enough for the desired effect, the proposed technological approach turned out to be satisfying and original. Cheeses with prebiotic fiber are not still widespread in the market.

Carbohydrate Fermentation Profile and Physiological Studies of Lactic Acid Bacteria from Native Raw Cow Milk

The aim of this study was to identify and evaluate the physiological studies of lactic acid bacteria from native raw cow milk. Cow milk samples were collected purposively from four different locations in Ibadan. The proximate analysis, pH and acidity of the milk samples were examined using standard procedures. Lactic acid bacteria (LAB) were isolated, characterized, and identified using both morphological, biochemical test, and Analytical profile index (API) system. The identified LAB were subjected to various physiological conditions such as growth at different temperature (15, 30, 45°C), pH (4, 6, 8) and NaCl concerntrations (4, 6, and 8%).The heterotrophic counts ranged between 3.1 ×107to 4.2 ×107CFU/mL and lactic acid bacteria counts ranged from 2.2× 107 to 3.8 × 107 CFU/mL. Thirty-five LAB isolates were randomly picked and identified as Lactobacillus (57.15%), Streptococcus (14.29%), Leuconostoc (8.57%), Pediococcus (8.57%), Lactococcus (5.71%) and Enterococcus (5.71%). The LAB isolates were further identified as Lactobacillus plantarum, Leuconostoc mesenteriodes, Lactococcus lactis, Lactobacillus acidiophilus and Lactobacillus bulgaricus based on API 50 test kit, and were able to grow at different physiological paramaters. This study shows that Lactobacillus strains isolated from raw cow milk had better physiological attributes. These LAB could be recommended for further assessment such as evaluation of probiotic potential properties and genomic analysis.

ISOLATION AND CHARACTERIZATION OF UNIQUE FRUCTOPHILIC LACTIC ACID BACTERIA FROM DIFFERENT FLOWER SOURCES.

This study was aimed to investigate Lactic acid bacteria (LAB) that contain an important group of bacterial strains such as fructophilic lactic acid bacteria that usually isolated from fructose rich niches. These groups of bacteria have been considered as probiotics, especially in animal applications. In this study these bacteria were isolated from 6 Plant sources (flowers) such as: Convolvulus arvensis, Hibiscus rosa-sinensis , Nerium oleander, Rosa rugosa, Tagetes erecta and Zinnia elegans. The bacterial isolates were identified by morphological and molecular methods through the detection of 16SrRNA gene. Carbohydrate fermentation profile as well as their antibacterial activity using the dual culture overlay assay was also detected. The results revealed that 5 types of different lactic acid bacteria were isolated included: Fructobacillus fructosus, Lactobacillus kunkeei, Enterococcus durans, Enterococcus faecium , and Lactobacillus brevis. These isolates showed variety in fermentation of carbohydrates. Also, all isolates exhibit inhibition effect against pathogenic bacteria (Staphylococcus auresو Pseudomonas aeruginosa) except Enterococcus faecium which showed no effect it.

Comparative Analysis of Lactobacillus gasseri and Lactobacillus crispatus Isolated From Human Urogenital and Gastrointestinal Tracts.

Lactobacillus crispatus and Lactobacillus gasseri are two of the main Lactobacillus species found in the healthy vaginal microbiome and have also previously been identified and isolated from the human gastrointestinal (GI) tract. These two ecological niches are fundamentally different, notably with regards to the epithelial cell type, nutrient availability, environmental conditions, pH, and microbiome composition. Given the dramatic differences between these two environments, we characterized strains within the same Lactobacillus species isolated from either the vaginal or intestinal tract to assess whether they are phenotypically and genetically different. We compared the genomes of the Lactobacillus strains selected in this study for genetic features of interest, and performed a series of comparative phenotypic assays including small intestinal juice and acid resistance, carbohydrate fermentation profiles, lactic acid production, and host interaction with intestinal Caco-2 and vaginal VK2 cell lines. We also developed a simulated vaginal fluid (SVF) to study bacterial growth in a proxy vaginal environment and conducted differential transcriptomic analysis between SVF and standard laboratory MRS medium. Overall, our results show that although strain-specific variation is observed, some phenotypic differences seem associated with the isolation source. We encourage future probiotic formulation to include isolation source and take into consideration genetic and phenotypic features for use at various body sites.

Diversity of lactic acid bacteria in dadih produced by either back-slopping or spontaneous fermentation from two different regions of West Sumatra, Indonesia.

Aim:Dadih samples from two different origins (Kamang and Gadut in West Sumatra) manufactured with different methods (back-slopping or spontaneous fermentation) were evaluated for the diversity of lactic acid bacteria (LAB).Materials and Methods:Four dadih samples manufactured with two different fermentation methods were obtained from Kamang and Gadut regions. Both genotypic and phenotypic characteristic (16S rRNA partial gene sequence analysis and carbohydrate fermentation profile) were used to analyze the diversity of dadih LAB population.Results:This study showed that LAB count in back-slopping fermented dadih was one log cycle higher than spontaneous fermented dadih. LAB isolates from the two regions were divided into three genera, namely Lactococcus, Lactobacillus, and Pediococcus. Sequencing results showed that 41.6% (five isolates) were identified as Lactococcus lactis ssp. lactis, 25% (three isolates) were identified as Lactobacillus plantarum ssp. plantarum, 16.6% (two isolates) were identified as L. lactis ssp. cremoris, and 8.3% (one isolate each) were identified as Pediococcus pentosaceus and Lactobacillus pentosus.Conclusion:Five species were determined in back-slopping fermented dadih, i.e., L. lactis ssp. lactis, L. lactis ssp. cremoris, L. plantarum ssp. plantarum, L. pentosus, and P. pentosaceus. On the other hand, spontaneous fermented dadih only contained three different species, namely L. lactis ssp. lactis, L. lactis ssp. cremoris, and L. plantarum ssp. plantarum. This research showed that back-slopping fermentation offers greater abundance and diversity compared to spontaneous fermentation in dadih.

<i>In Vitro</i> Antimicrobial Characterization of <i>Lactobacillus</i> Isolates Towards Their Use as Probiotic Alternatives to Antibiotic Growth Promoters

In the present study, the probiotic potential of Lactobacillus isolates selected from fecal samples of farmyard chickens and ducks was scientifically validated for their use as alternatives to antibiotics in poultry. A total of 129 Lactobacillus isolates were characterized of which four produced inhibitory substances with antimicrobial activities. They were further identified on the basis of their carbohydrate fermentation profile and High-Resolution Melting analysis as Lactobacillus paracasei MW-37CGZ, Lactobacillus paracasei MW-38CGZ, Lactobacillus plantarum MW-48CGZ and Lactobacillus plantarum MW-18CGZ. The obtained results revealed that L. plantarum MW-18CGZ and L. paracasei MW-37CGZ showed strong antagonistic activities against human (nine) and zoonotic pathogens (eleven). The antimicrobial substance produced by L. plantarum MW-18CGZ was found to be proteinaceous, thus indicating that this substance may belong to a group of potent antimicrobial peptides produced by some microorganisms including lactic acid bacteria (LAB). Both viable and non-viable cells of the four isolates demonstrated good hydrophobicity in xylene with L. plantarum MW-48CGZ exhibiting higher hydrophobicity than other isolates (77.64±5.18%). They were susceptible to chloramphenicol, clindamycin, ampicilin and erythromycin with Minimum Inhibitory Concentration (MIC) below cut-off values established by the European Food Safety Authority (EFSA). Among the four Lactobacillus, L. plantarum MW-18CGZ and L. paracasei MW-37CGZ displayed high autoaggregation and coaggregation towards pathogens and all isolates survived in low-pH, high bile salt concentrations and none exhibited virulent factors. According to the obtained results, L. plantarum MW-18CGZ and L. paracasei MW-37CGZ could be considered as future biotherapeutic substitutes for antibiotics to reduce antibiotic residues in food derived from poultry as well as the generation and spread of antibiotic resistance.

Lactobacillus curtus sp. nov., isolated from beer in Finland.

A Gram-stain-positive, catalase-negative and short-rod-shaped organism, designated VTT E-94560, was isolated from beer in Finland and deposited in the VTT culture collection as a strain of Lactobacillus rossiae. However, the results of 16S rRNA gene sequence analysis showed that VTT E-94560 was only related to Lactobacillus rossiae JCM 16176T with 97.0 % sequence similarity, lower than the 98.7 % regarded as the boundary for the species differentiation. Additional phylogenetic studies on the pheS gene, rpoA gene and 16S-23S rRNA internally transcribed spacer region further reinforced the taxonomically independent status of VTT E-94560 and its related Lactobacillus species including L. rossiae and Lactobacillus siliginis. Strain VTT E-94560 also exhibited several differences in its carbohydrate fermentation profiles from those related Lactobacillus species. In addition, DNA-DNA relatedness between VTT E-94560 and these two type strains was 4 % (L. rossiae JCM 16176T) and 12 % (L. siliginins JCM 16155T), respectively, which were lower than the 70 % cut-off for general species delineation, indicating that these three strains are not taxonomically identical at the species level. These studies revealed that VTT E-94560 represents a novel species, for which the name Lactobacillus curtus sp. nov. is proposed. The type strain is VTT E-94560T (=JCM 31185T).

Lactobacillus colini sp. nov., isolated from Northern Bobwhite (Colinus virginianus).

Biochemical and molecular studies were performed on five unknown bacterial strains isolated from the intestinal contents of Northern Bobwhites (Colinus virginianus) collected from western Texas, USA. The strains were Gram-stain-positive, catalase-negative, non-spore-forming rods arranged in single cells, pairs or short chains. Colonies on Columbia blood agar are circular, flat, entire, approximately 0.5-1.5 mm in diameter and surrounded with a zone of alpha-haemolysis at after incubation for 48 h at 37 °C. Colonies on MRS agar are umbonate with irregular edge, opaque and approximately 1-1.5 mm in diameter after incubation for 48 h. The 16S rRNA gene sequences of the isolates were identical and the highest sequence similarity (97 %) was found to the type strains of Lactobacillus gasseri, L. johnsonii and L. taiwanensis. The strains were distinguishable from related species of the genus Lactobacilluson the basis of carbohydrate fermentation, enzymatic production and fatty acid profiles. The peptidoglycan type is l-Lys-d-Asp (A4α). The DNA G+C content is 35.6 mol%. Major cellular fatty acids are C14 : 0, C16 : 0 and C18 : 1 ω9c. Based on phenotypic, phylogenetic and chemotaxonomic information, the strains represent a novel species of the genus Lactobacillus for which the name Lactobacillus colini sp. nov. is proposed. The type strain is 111144 L1T (=DSM 101872T=KCTC 21086T).

In Vitro Assessment of the Probiotic Potential of Lactococcus lactis LMG 7930 against Ruminant Mastitis-Causing Pathogens.

Mastitis in dairy ruminants is considered to be the most expensive disease to farmers worldwide. Recently, the intramammary infusion of lactic acid bacteria has emerged as a potential new alternative to antibiotics for preventing and treating bovine mastitis. In this study we have investigated in vitro the probiotic potential of Lactococcus lactis LMG 7930, a food-grade and nisin-producing strain, against mastitis-causing pathogens. We have characterized its carbohydrate fermentation and antibiotic susceptibility profiles, cell surface properties and antimicrobial activity, as well as its capabilities to adhere to and inhibit the invasion of pathogens into the bovine mammary epithelial cell line BME-UV1d. We found that L. lactis LMG 7930 was sensitive to tested drugs, according to the EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP), and showed an improved carbohydrate fermentation capacity compared to starter strains. Moreover, the strain exhibited antagonistic properties towards many of the pathogens tested. It presented medium surface hydrophobicity, a low basic property and no electron acceptor capability. It showed low auto-aggregation and no co-aggregation abilities towards any of the tested pathogens. The strain was one of the most adhesive to bovine mammary epithelial cells among tested bacteria, but its internalisation was low. The strain did not affect significantly pathogen invasion; however, a trend to decrease internalization of some pathogens tested was observed. In conclusion, our results suggest that this strain might be a promising candidate for the development of new strategies of mastitis control in ruminants. Future investigations are needed to evaluate its safety and efficacy under field conditions.

Characterization of Bacteriocin-Producing Lactic Acid Bacteria Isolated from Native Fruits of Ecuadorian Amazon.

Tropical, wild-type fruits are considered biodiverse "hotspots" of microorganisms with possible functional characteristics to be investigated. In this study, several native lactic acid bacteria (LAB) of Ecuadorian Amazon showing highly inhibitory potential were identified and characterized. Based on carbohydrate fermentation profile and 16S rRNA gene sequencing, seven strains were assigned as Lactobacillus plantarum and one strain as Weissella confusa. Using agar-well diffusion method the active synthetized components released in the neutralized and hydroxide peroxide eliminated cell-free supernatant were inhibited by proteolytic enzymes, while the activity was maintained stable after the treatment with catalase, lysozyme, α-amylase and lipase suggesting their proteinaceous nature. The inhibitory activity was stimulated by acidic conditions, upon exposure to high heat and maintained stable at different ranges of sodium chloride (4-10%). The DNA sequencing analysis confirmed the presence of plw structural gene encoding for plantacirin W in the selected L. plantarum strains. Moreover, we showed that the active peptides of Cys5-4 strains contrast effectively, in a bactericidal manner, the growth of food borne E. coli UTNEc1 and Salmonella UTNSm2, with about tree fold reduction of viable counts at the early stage of the target cell growth. The results indicated that the bacteriocin produced by selected native lactic acid bacteria strains has elevated capacity to suppress several pathogenic microorganisms implying their potential as antimicrobial agents or food preservatives.

Exploring the biodiversity of two groups of Oenococcus oeni isolated from grape musts and wines: Are they equally diverse?

One hundred and four Oenococcus oeni isolates were characterised by the carbohydrate fermentation (CH) profile and DNA fingerprinting. Forty-four isolates came from grape must, and 60 from wines sampled at the end of alcoholic fermentation or during malolactic fermentation. The grape must isolates fermented more CH than the wine isolates. In genotypical terms, no clear boundary between grape must and wine isolates was found. Diversities were deduced by considering the isolates of grape must and of wine separately and jointly. By considering only CH fermentation abilities, the group of grape must isolates gave higher diversity index (DICH) values than those isolated from wine; i.e., these isolates were metabolically more diverse. The contrary occurred when the DNA fingerprints were used to calculate DIRAPD-VNTR: wine isolates were genotypically more diverse than grape must ones. With a polyphasic approach, which considered metabolic and genotypic data, the diversity index of both isolate groups (from grape must and wine) was the same, 0.993, which was slightly lower than that calculated from all the isolates (0.997).

Identification and antibiotic resistance of Lactobacilli isolated from raw cow’s milk of Oujda City (Morocco)

ABSTRACTIn this study, a Lactobacillus strain was isolated from raw cow milk. It was tentatively identified at the species level according to its carbohydrate fermentation profile and phenotype characteristics as Lactobacillus paracasei KSNM. The susceptibility of the identified Lactobacillus to 23 antibiotics was performed using the disc diffusion testing method. Inhibition zone diameters were measured and expressed in terms of sensitive, intermediate or resistant. KSNM strain was sensitive toward; amoxicillin, ampicillin, amoxyclav (amoxicillin + clavulanic acid), tetracycline, macrolides, sulfamides/trimethoprim, and rifampicin. But, it expressed intermediate sensitivity toward; cefamandole, cefaclor, and cephalothin. However, it was resistant to penicillin G, aminoglycosides, quinolones, ciprofloxacin, lincomycin, nitroxolin, and a large number of cephalosporins, which included cefoxitin, cefotaxime, and ceftriaxone.

Probiotic activity of Bifidobacteria from infant faeces

In the present study four isolates belonging to three bifidobacterial species with probiotic properties were isolated and identified from the faeces of breast fed infants and incorporated in the preparation of a nutraceutical whey based malt food. Identification of isolates to the genus Bifidobacteria was based on phenotypic characteristics like the unique pleomorphic morphology and carbohydrate fermentation profile. Molecular tools like 16S rRNA targeted genus and species specific mPCR were used for confirmation. The four isolates (of 3 species) identified wereB. longum(IB10 and IB12)B. breve (IB39)and B.bifidum (IB42). The nucleotide sequences of the identified species were submitted to the GenBank for acquisition of accession number. The identified species were screened for probiotic properties like bile tolerance, antimicrobial activity and tolerance to acidity. All the four isolates showed more than 80 per cent viability in the presence of 0.4, 0.8 and 1 per cent of bile salt. IsolateB.longum (IB10)showed maximum antimicrobial activity against Bacillus cereus (zi3.03 ± 0.019 mm), Staphylococcus aureus (zi3.00 ± 0.031mm), Escherichia coli(zi2.98 ± 0.043 mm) and Pseudomonas aeruginosa (zi3.03 ± 0.051 mm) in the cell free supernatant. All the four bifidobacterial isolatesshowed more than 80 per centviability atpH 3.B.longum (IB10)was a better probiotic when compared to other isolates as it had maximum antimicrobial activity and tolerance to bile and acidity.

English

Probiotics, as functional food components, are recognized as safe microorganisms of viable single or mixed cultures with claimed health promoting effects on their host by improving the properties of the indigenous intestinal microflora. In the present study, a total of ten probiotic lactic acid bacteria were isolated comprising Lactobacillus acidophilus, Lactobacillus brevis, Bifidobacterium sp. and Streptococcus thermophilus. According to morphological, physiological, and biochemical assays, all the isolates were gram positive, endospore negative, catalase negative, non-motile, and possessed bile salt hydrolase activity characteristic to probiotic bacteria. Carbohydrate fermentation profiles ensured the presumptive identification. Importantly, the isolates were resistant to artificial gastric juice environment at pH 2.2, and their resistance decreased after 24 h of incubation at 37°C. Moreover, bile salt tolerance was observed not only at 0.05, 0.1, 0.15, and 0.3% artificial bile from 0 to 4 h of incubation at 37°C, but also started multiplication after 16 h. The best phenol tolerance found at 0.1 to 0.2% phenol, very low at 0.3 and 0.4% phenol after 12 and 24 h of incubation, respectively. They also possessed excellent tolerance against 1 to 7% NaCl. Because of being probiotic potentiality, the best isolates can be used for probiotic product development in future. Key words: Probiotics, artificial bile, artificial gastric juice, bile salt hydrolase, carbohydrate fermentation.

Biochemical Characterization of Probiotics Available in Bangladesh

The pervasive beneficial effects of probiotics are important for the maintenance of mammalian homeostasis. The probiotic products are consumed by people in their various forms available in Bangladesh. In this context, this study is taken into consideration to identify and characterize bacteria to confirm the scientific data needed for improvement in probiotic products as current therapies. Five probiotic samples were collected from pharmaceutical companies available in the retail pharmacy, Rajshahi. The probiotic samples are tested before expiration dates as marked on manufacturer packages. The culture media used were Czapek Dox (pH 5.3), MRS and nutrient broth and agar for the investigation of lactic acid bacteria. The identified lactic acid bacteria (LAB) were lactobacillus acidophyllus (LAB 1), Lactobacillus bulgaricus (LAB 2), Lactococcus lactis (LAB 3) and Biffidobacterium biffidum (LAB 4) based on morphological characteristics, catalase activities, milk coagulation, carbohydrate fermentation profiles, resistance to antibiotics and other biochemical tests. The rejuvenation of probiotics particularly LAB from the probiotic samples can be used in other purposes such as biopreservation of lemon, orange juices with better tastes and fermented products like curds as well as hygienic qualities of other dairy products.