Characterization and distribution of lactic acid bacteria in cassava fermentation during fufu production

[Lactic starter cultures to improve the oat bioactive compounds]

The objective of this work was to study lactic fermentation as a biostrategy to enhance the antioxidant activity of oats. The adaptability of 31 strains of lactic bacteria (LB) in an oats/water system (OWS/SAA) was evaluated, measuring growth, acidification and fermentation activity (impedimetric method; detection time [DT], maximum rate of conductance change [MRCC/VMCC] and percentage of conductance change [PCC]). Moreover, the content of phenolic compounds (PC) was determined using the Folin-Ciocalteu method (gallic acid equivalents [GAE]), free peptides and amino acids and free radical scavenging activity (DPPH^• and ABTS^•+ methods) of methanolic and aqueous extracts obtained from fermented OWS/SAAs (fOWS/SAAf) were determined. Six strains have shown the best adaptability to SAA, with high values of VMCC (0.34-0.47 μS/min) and PCC (53.6-66.6%), and low values of DT (≤ 3 h). In these f/OWS/SAAf the chemical composition was also modified (PC concentration, peptides and free amino acids) with strain-dependent behavior. The PC content in f/OWS/SAAf using these six strains (29.1-36.9 μg GAE/ml) was higher than the control content in OWS/SAA control (17.1 ± 1.9 μg GAE/ml). An increase (9-25.5%) in antioxidant activity in f/OWS/SAAf methanolic extracts was detected using both methods. Minor modifications were observed in the peptide and free amino acid content of SAA and their antioxidant activity. Our results show LB ability to adapt to oat as fermentation substrate and increase the content of its antioxidant compounds.

Cyanide, haematology and histopathology profiles of albino rats fed with 'Fufu'-based diets produced from mixed starter cultures

The cyanide, haematology and histopathology profiles of white albino rats fed with ‘fufu’-based diets were monitored. The cassava tubers were subjected into different processing operations: spontaneous-soaked traditional method (SWI), grated before spontaneously-fermented without starter culture (CWI) and those grated, blanched at 65 °C for 15 min before fermented with microorganisms isolated, purified and identified from spontaneously fermented ‘fufu’ categorized into Bacteria only (BAP), Bacteria and Yeast (BYP), Yeast only (YAP), Bacteria and Mould (BMP), Mould and Yeast (MYP) and Mould only (MAP) and were oven dried and milled. The commercial ready-to-eat ‘Fufu’ (CWF) was served as control for laboratory processed samples. Albino rats of the wister strain with four (4) rats per group were fed with 50 % of Commercial vital feed (CVF) and 50% each of the remaining nine (9) “Fufu” samples in ratio 1:1 before haematology and histopathology profile of the animals were investigated. It was found out that Samples BMP and MAP had abnormal high Neutrophil (58–60; 41–42 %) lower Lymphocyte (40–43; 58–61 %), lower Packed cell volume (46–48; 45–47 %) and higher cyanide in the blood (0.004–0.006 mg/L) with sample BMP highest white blood cell (23–24 × 10⁹/L) and sample MAP least white blood cell (6.5–6.6 × 10⁹/L) when compared with other samples which were within the acceptable recommended values for animal studied for haematology and histopathology profiles. The “fufu” samples had reduced cyanide levels ranging from 0.001 mg/L to 0.006 mg/L in the blood of the animals assayed due to the processing operations used. Therefore, combined use of bacteria isolated as starter cultures in the production of odourless “Fufu” have acceptable haematology, histopathology and reduced cyanide level which suggests the suitability in terms of safety for human consumption.

Comparative study of host-associated and commercial probiotic effects on serum and mucosal immune parameters, intestinal microbiota, digestive enzymes activity and growth performance of roach (Rutilus rutilus caspicus) fingerlings

The study aimed to isolate host-associated probiotic (HAP) lactic acid bacteria from intestine of adult Caspian roach and compare the efficacy of HAP with a commercially available probiotic strain (Pediococcus acidilactici) on the growth and feed utilisation, digestive enzymes and systemic and mucosal immune system of roach fingerling. The HAP strain isolated from roach intestine was Enterococcus faecium strain CGMCC1.2136. The experiment was a simple completely randomized design and lasted for eight weeks. Two hundred and seventy fish with an average weight of 12 g randomly distributed into nine tanks. The trial consisted of three treatments with three respective replications. During the experimental period, fish received basal diet without any bacterial supplementation (as the control group), basal diet enriched with 10⁸ CFU g^-1 HAP or 10⁷ CFU g^-1 CP. At the end of the experiment, serum immune parameters of those fish fed HAP including alkaline phosphatase activity, total protein content, total immunoglobulin level, lysozyme activity and complement activity (ACH50) were significantly higher that other experimental groups (P < 0.05). Similarly, dietary supplementation of HAP resulted in better mucosal immune parameters in comparison to control group and commercial probiotic administration (P < 0.05). Intestinal heterotrophic bacteria and autochthonous LAB counts of those fish fed HAP were significantly higher than other experimental groups at the end of the experiment as well as 15 days seizing probiotic administrations (P < 0.05). Fish fed with HAP containing diet presented significantly higher amylase, lipase and protease activity in comparison to the CP fed fish and the control group (P < 0.05). Growth indices of those fish fed HAP were significantly higher than other treatments (P < 0.05). The highest carcass protein and ash content along with the lowest body moisture content belonged to those fish received HAP (P < 0.05). In conclusion, the use host-HAP resulted in better immune competence and growth performance and it seems aquaculture sector should probably focus on the development of probiotics isolated from the cultured species instead of using terrestrial probiotics with greatly different requirements and environmental conditions.

Drying kinetic of industrial cassava flour: Experimental data in view

In this data article, laboratory experimental investigation results on drying kinetic properties: the drying temperature (T), drying air velocity (V) and dewatering time (Te), each of the factors has five levels, and the experiment was replicated three times and the output: drying rate and drying time obtained, were observed. The experiment was conducted at National Centre for Agricultural Mechanization (NCAM) for a period of eight months, in 2014. Analysis of variance was carried out using randomized complete block design with factorial experiment on each of the outputs: drying rate and drying times of the industrial cassava flour. A clear picture on each of these outputs was provided separately using tables and figures. It was observed that all the main factors as well as two and three ways interactions are significant at 5% level for both drying time and rate. This also implies that the rate of drying grated unfermented cassava mash, to produce industrial cassava flour, depend on the dewatering time (the initial moisture content), temperature of drying, velocity of drying air as well as the combinations of these factors altogether. It was also discovered that all the levels of each of these factors are significantly difference from one another. In summary, the time of drying is a function of the dewatering time which was responsible for the initial moisture content. The higher the initial moisture content the longer the time of drying, and the lower the initial moisture content, the lower the time of drying. Also, the higher the temperature of drying the shorter the time of drying and vice versa. Also, the air velocity effect on the drying process was significant. As velocity increases, rate of drying also increases and vice versa. Finally, it can be deduced that the drying kinetics are influenced by these processing factors.

Occurrence of Regulated Mycotoxins and Other Microbial Metabolites in Dried Cassava Products from Nigeria

Dried cassava products are perceived as one of the potential sources of mycotoxin ingestion in human foods. Processing either contributes to the reduction of toxins or further exposes products to contamination by microorganisms that release metabolic toxins into the products. Thus, the prevalence of microbial metabolites in 373 processed cassava products was investigated in Nigeria. With the use of liquid chromatography tandem-mass spectrometry (LC-MS/MS) for the constituent analysis, a few major mycotoxins (aflatoxin B₁ and G₁, fumonisin B₁ and B₂, and zearalenone) regulated in food crops by the Commission of the European Union were found at concentrations which are toxicologically acceptable in many other crops. Some bioactive compounds were detected at low concentrations in the cassava products. Therefore, the exposure of cassava consumers in Nigeria to regulated mycotoxins was estimated to be minimal. The results provide useful information regarding the probable safety of cassava products in Nigeria.

Microbiology of keribo fermentation: an Ethiopian traditional fermented beverage

Keribo is an indigenous traditional fermented beverage and is being served on holidays, wedding ceremony and also used as sources of income of many households in Jimma zone. The aim of this study was to document the microbiology of the product and antibiotic susceptibility patterns of LAB. Samples of Keribo were collected from Jimma town and four of its districts. Keribo was fermented in the laboratory following the traditional techniques for microbial succession monitored at 6 h intervals. Finally, dominant LAB was evaluated for their antibiotic susceptibility patterns against eight antibiotics. Samples of Keribo from open markets and households in Jimma zone showed average Lactic Acid Bacteria (LAB), Aerobic Mesophilic Bacteria (AMB), Aerobic Spore-formers (ASF) and yeasts with mean counts of (log CFU mL(-1)) 2.70 +/- 2.07, 2.34 +/- 2.37, 4.96 +/- 2.80 and 2.01 +/- 0.60, respectively. The mean counts of Enterobacteriaceae, staphylococci and moulds were below detectable levels. The early stage was dominated by AMB and ASF. However, the mean counts of LAB increased exponentially for the first 30 h and remain constant thereafter. Leuconostoc mesenteroides, identified as the most dominant LAB, were found to be susceptible to penicillin G, gentamicin, ampicilin, chloramphenicol, amikacin, bacitracin and norfloxacin but resistant to vancomycin.

Microbiological Safety Assessment of Fermented Cassava Flour "Lafun" Available in Ogun and Oyo States of Nigeria

The microorganisms involved in the fermentation and spoilage of fermented cassava flour were investigated. The water samples used at the different processing sites were also investigated to determine their safety status. There was predominance of Staphylococcus aureus, Aspergillus spp., and Escherichia coli in all samples. Coliforms were observed to be present in all of the processing water. In the fermented cassava flour, the total bacterial count ranged between 4.9 × 10⁶ cfu/mL from Eleso, Bakatari, and Oja Odan processing sites and 8.10 × 10⁶ cfu/mL in Eruku processing site. The majority of the microorganisms involved in the spoilage of “lafun” were found to be Aspergillus niger which ranged between 4.6 × 10⁵ cfu/mL in Eleso and 8.1 × 10⁵ cfu/mL in Kila. The control sample prepared in the laboratory had a low microbial load compared to samples collected from various sites and markets.

The use of microorganisms in increasing the protein yield of cassava (Manihot esculenta Crantz) peel wastes

Growth and microbial protein production on hydrolyzed cassava peel waste by Trichoderma viride and Lactobacillus delbrueckii NRRL B-763 were investigated. Trichoderma viride was selected based on its high cellulase activity on filter paper (2.91 mg glucose/mL), cotton wool (3.08 mg glucose/mL) and carboxymethylcellulose (3.46 mg glucose/ mL) while Lactobacillus delbrueckii NRRL B-763 produced 5.84 mg protein/g in cassava peel after 72 h. Samples of cassava peel were hydrolyzed with the solutions of HCl, H2SO4 and NaOH at 0.5% concentration. The hydrolysate was neutralized to pH 6.5 and supplemented with KH2PO4 (5% w/v), urea (2.7% w/v) and (NH4)2SO4 (9% w/v). The hydrolysates produced by the solutions of HCl contained higher reducing sugar and soluble sugar content than H2SO4 and NaOH hydrolysates. The culture of Trichoderma viride was used in single culture fermentation of hydrolyzed cassava peels or in mixed culture fermentation with Lactobacillus delbrueckii NRRL B-763. Protein yield produced in 0.5% HCl hydrolysates was significantly (p ≤ 0.01) higher than that in H2SO4. The unhydrolyzed control samples produced the lowest protein. This study demonstrated the potential of cassava peel waste as a substrate for a recycling process and by- product recovery.

Hypolipidemic effects of lactic acid bacteria fermented cereal in rats

BACKGROUND

The objectives of the present study were to investigate the efficacy of the mixed culture of Lactobacillus acidophilus (DSM 20242), Bifidobacterium bifidum (DSM 20082) and Lactobacillus helveticus (CK60) in the fermentation of maize and the evaluation of the effect of the fermented meal on the lipid profile of rats.

METHODS

Rats were randomly assigned to 3 groups and each group placed on a Diet A (high fat diet into which a maize meal fermented with a mixed culture of Lb acidophilus (DSM 20242), B bifidum (DSM 20082) and Lb helveticus (CK 60) was incorporated), B (unfermented high fat diet) or C (commercial rat chow) respectively after the first group of 7 rats randomly selected were sacrificed to obtain the baseline data. Thereafter 7 rats each from the experimental and control groups were sacrificed weekly for 4 weeks and the plasma, erythrocytes, lipoproteins and organs of the rats were assessed for cholesterol, triglyceride and phospholipids.

RESULTS

Our results revealed that the mixed culture of Lb acidophilus (DSM 20242), B bifidum (DSM 20082) and Lb helveticus (CK 60) were able to grow and ferment maize meal into 'ogi' of acceptable flavour. In addition to plasma and hepatic hypercholesterolemia and hypertriglyceridemia, phospholipidosis in plasma, as well as cholesterogenesis, triglyceride constipation and phospholipidosis in extra-hepatic tissues characterized the consumption of unfermented hyperlipidemic diets. However, feeding the animals with the fermented maize diet reversed the dyslipidemia.

CONCLUSION

The findings of this study indicate that consumption of mixed culture lactic acid bacteria (Lb acidophilus (DSM 20242), Bifidobacterium bifidum (DSM 20082) and Lb helveticus (CK 60) fermented food results in the inhibition of fat absorption. It also inhibits the activity of HMG CoA reductase. This inhibition may be by feedback inhibition or repression of the transcription of the gene encoding the enzyme via activation of the sterol regulatory element binding protein (SREBP) transcription factor. It is also possible that consumption of fermented food enhances conversion of cholesterol to bile acids by activating cholesterol-7α-hydroxylase.

Protein improvement in Gari by the use of pure cultures of microorganisms involved in the natural fermentation process

The ability of microorganisms involved in cassava mash fermentation to produce and improve protein value by these microorganisms during fermentation was studied. Standard microbiological procedures were used to isolate, identify and determine the numbers of the organisms. Alcaligenes faecalis, Lactobacillus plantarum, Bacillus subtilis, Leuconostoc cremoris, Aspergillus niger, A. tamari, Geotrichum candidum and Penicillium expansum were isolated and identified from cassava waste water while standard analytical methods were used to determine the ability of the isolates to produce linamarase and the proximate composition, pH and titrable acidity of the fermenting mash. The linamarase activity of the isolates ranged from 0.0416 to 0.2618 micromol mL(-1) nmol(-1). Bacillus subtilis, A. niger, A. tamari and P. expansum did not express any activity for the enzyme. Protein content of mash fermented with mixed fungal culture had the highest protein value (15.4 mg/g/dry matter) while the raw cassava had the least value (2.37 mg/g/dry matter). The naturally fermented sample had the least value for the fermented samples (3.2 mg/g/dry matter). Carbohydrate and fat contents of naturally fermented sample were higher than values obtained from the other fermented samples. Microbial numbers of the sample fermented with mixed bacterial culture was highest and got to their peak at 48 h (57 x 10(8) cfu g(-1)). pH decreased with increase in fermentation time with the mash fermented by the mixed culture of fungi having the lowest pH of 4.05 at the end of fermentation. Titrable acidity increased with increase in fermentation time with the highest value of 1.32% at 96 h of fermentation produced by the mixed culture of fungi. Thus fermentation with the pure cultures significantly increased the protein content of mash.

Diversity of lactic acid bacteria from Hussuwa, a traditional African fermented sorghum food

The diversity of lactic acid bacteria associated with Hussuwa fermentation, a Sudanese fermented sorghum food, was studied using a polyphasic taxonomical approach. Predominant strains could be well characterised based on a combination of phenotypic tests and genotypic methods such as ARDRA, rep-PCR and RAPD-PCR, as well as 16S rRNA gene sequencing of representative strains. Thus, the majority (128 of 220, 58.3%) of strains exhibited phenotypic properties typical of heterofermentative lactobacilli and of these, 100 strains were characterised more closely using the genotyping methods. The majority (97/100) strains could be characterised as Lactobacillus fermentum strains. Seventy-two of 220 strains (32.7%) showed phenotypic properties that are characteristic of pediococci. Of 41 selected strains investigated by genotyping techniques, 38 (92.7%) could be characterised as Pediococcus acidilactici strains, while three (7.3%) could be characterised as Pediococcus pentosaceus strains. The Hussuwa fermentation thus appears to be dominated by L. fermentum strains and P. acidilactici strains. For this reason, we selected representative and predominant strains as potential starter cultures for Hussuwa fermentation. These strains, L. fermentum strains BFE 2442 and BFE 2282 and P. acidilactici strain BFE 2300, were shown on the basis of RAPD-PCR fingerprinting to predominate in a model fermentation when used as starter cultures inoculated at 1 x 10(6) CFU/g and to lower the pH of the fermentation to below pH 4.0 within 48 h. These cultures should be studied for further development as starter preparations in pilot scale studies in actual field fermentations.

Microbial population present in fermented beverage 'cauim' produced by Brazilian Amerindians

The Tapirapé Amerindians of the Tapi'itãwa tribe produce several fermented foods and beverages among them the beverage called 'cauim'. This beverage is the main staple food for infants until two years old and their parents. For producing the beverage, several substrates are used, such as: cassava, rice, corn, maize and peanuts. The fermentation using mainly cassava was accomplished and samples were collected for chemical and microbiological analysis. A progressive acidification during the fermentation was observed and pH value decreased from 5.5 to 3.4. Lactic acid was the most important fermentation metabolite found but significant amounts of ethanol and acetic acid were also observed. The microbial load was high at the beginning of the fermentation, bacterial population was about 6.8 log cfu/ml and yeast population was 3.7 log cfu/ml. A total of 355 bacteria were isolated and identified. All the isolates were grouped into Gram-negative (3.5%), Gram-positive non-sporulating (78%) and Gram-positive sporulating bacteria (18.5%). Lactic acid bacteria increased from the beginning of fermentation and became the dominant microorganism throughout the fermentation. Species of bacteria were varied and they were found to be Lactobacillus pentosus, L. plantarum, Corynebacterium xerosis, C. amylocolatum, C. vitarumen, Bacillus cereus, B. licheniformis, B. pumilus, B. circulans and Paenibacillus macerans. The species L. pentosus and L. plantarum were the dominant bacteria and were present in all the periods of evaluation of the samples.

Diversity and technological properties of predominant lactic acid bacteria from fermented cassava used for the preparation of Gari, a traditional African food

Traditional fermentation of cassava is dominated by a lactic acid bacteria (LAB) population. Fermentation is important for improving product flavour and aroma as well as safety, especially by reduction of its toxic cyanogenic glucosides. The production of Gari from cassava in Benin typically occurs on a household or small industrial scale, and consequently suffers from inconsistent product quality and may not always be safe for consumption. Therefore, the diversity of LAB from a typical cassava fermentation for the preparation of Gari, and their technologically relevant characteristics were investigated with a view towards selection of appropriate starter cultures. A total of 139 predominant strains isolated from fermenting cassava were identified using phenotypic tests and genotypic methods such as rep-PCR and RAPD-PCR. DNA-DNA hybridisation and sequencing of the 16S rRNA genes were done for selected strains. Lactobacillus plantarum was the most abundantly isolated species (54.6% of isolates), followed by Leuconostoc fallax (22.3%) and Lactobacillus fermentum (18.0%). Lactobacillus brevis, Leuconostoc pseudomesenteroides and Weissella paramesenteroides were sporadically isolated. The L. plantarum strains were shown to be better acid producers and capable of faster acid production than the L. fallax or L. fermentum strains. The incidence of beta-glucosidase (linamarase) activity was also highest among strains of this species. Production of antagonistic substances such as H2O2 and bacteriocins, however, was more common among L. fallax and L. fermentum strains. Strains of all three species were capable of utilising the indigestible sugars raffinose and stachyose. Therefore, a starter culture containing a mixture of strains from all three species was recommended.

Souring and breakdown of cyanogenic glucosides during the processing of cassava into akyeke

The population and composition of the lactic acid bacteria microbiota as well as the content of cyanogenic glucosides occurring at various stages of fermentation and subsequent processing of cassava roots into akyeke, a steamed sour cassava meal, were investigated. The number of lactic acid bacteria and percentage titratable acidity increased during 5 days of fermentation, but decreases were observed in the subsequent operations of 'washing' the dough with water followed by partial drying and steaming. In field and laboratory samples, Lactobacillus plantarum accounted for 59.3% and 52.3%, Lactobacillus brevis 23.3% and 22.8% and Leuconostoc mesenteroides subsp. cremoris 14.5% and 15.8%, respectively, of all lactic acid bacteria isolated at various stages of fermentation and processing. A reduction of about 98% occurred in the total cyanogens (CN) content of cassava roots during processing, from 69.3 to 1.4 and 110.3 to 2.8 mg CN equivalent/kg dry weight for laboratory and field samples of akyeke, respectively.

Antimicrobial interactions of microbial species involved in the fermentation of cassava dough into agbelima with particular reference to the inhibitory effect of lactic acid bacteria on enteric pathogens

Lactic acid bacteria, Bacillus species and yeasts are involved in the fermentation of cassava dough into agbelima. Microbial interactions within and between these groups of microorganisms were investigated in addition to the survival of five enteric pathogens inoculated into agbelima under various conditions. Nine out of 10 cultures of lactic acid bacteria isolated at the end of agbelima fermentation showed inhibitory effect against 10 cultures of lactic acid bacteria isolated at the start of fermentation. Only 3 out of 10 isolates of Bacillus subtilis were inhibited by 10 isolates of lactic acid bacteria tested. No interactions were observed between yeasts and the lactic acid bacteria, whereas three of the Bacillus isolates showed inhibitory effects against the yeasts. Twelve isolates of Lactobacillus plantarum tested inhibited the growth of an isolate each of Lactobacillus fermentum and Lactobacillus brevis but none tested positive for bacteriocin production. The antimicrobial effect of the lactic acid bacteria was attributed to acid production. In fermenting cassava dough, enteric pathogens survived to different extents depending on pH and their sensitivity to acids. Vibrio cholerae C-230, Salmonella typhimurium 9 and Salmonella enteritidis 226 were not detectable in 10 g of sample after 4 h when inoculated into the 48-h fermented product, agbelima, whereas Shigella dysenteriae 2357T and Escherichia coli D2188 were detectable up to 8 h in the product.

Microbial modification of the texture of grated cassava during fermentation into akyeke

The traditional akyeke inoculum and fermenting akyeke, an indigenous cassava product, were investigated to identify microbial species responsible for the modification of cassava texture during fermentation. Both field and laboratory samples were examined and only some cultures isolated on Plate Count Agar and Malt Extract Agar were found to be capable of causing a softening of cassava tissue when plated directly on sterile cassava slices. The cassava tissue softening isolates on PCA were tentatively identified as Bacillus subtilis and isolates on MEA as Candida tropicalis and Zygosacchromyces florentinus. The population of B. subtilis in the laboratory sample of inoculum was found to be 2.4 x 10(9) cfu g(-1) and increased during dough fermentation from 1.1 x 10(7) to 3.5 x 10(9) cfu g(-1) after 96 h. C. tropicalis was present in the inoclum at 3.0 x 10(9) cfu g(-1) and increased during dough fermentation from 3.2 x 10(6) to 6.9 x 10(7) cfu g(-1) whilst Z. florentinus was present in the inoclum at 9.1 x 10(8) cfu g(-1) and increased from 8.1 x 10(5) to 7.5 x 10(6) cfu g(-1) during dough fermentation.

Use of starter cultures of lactic acid bacteria and yeasts in the preparation of togwa, a Tanzanian fermented food

Starter cultures of lactic acid bacteria (Lactobacillus brevis, Lactobacillus cellobiosus, Lactobacillus fermentum, Lactobacillus plantarum and Pediococcus pentosaceus) and yeasts (Candida pelliculosa, Candida tropicalis, Issatchenkia orientalis and Saccharomyes cerevisiae) isolated from native togwa were tested singly or in combination for their ability to ferment maize-sorghum gruel to produce togwa. All species of bacteria showed an ability to ferment the gruel as judged by lowering the pH from 5.87 to 3.24-3.49 and increasing the titratable acidity from 0.08% to 0.30-0.44% (w/w, lactic acid) in 24 h. Yeasts used singly showed little activity within 12 h, but lowered the pH to 3.57-4.81 and increased the acidity to 0.11-0.21% in 24 h. Yeasts in co-culture with lactic acid bacteria (LAB) had a modest effect on the final acidity (P<0.05). The number of lactic acid bacteria and yeasts increased while the Enterobacteriaceae decreased with fermentation time. The pH was lowered and lactic acid produced significantly (P<0.05) fastest in natural togwa fermentation and in samples fermented by L. plantarum or L. plantarum in co-culture with I. orientalis. The content of fermentable sugars was reduced during fermentation. Most volatile flavour compounds were produced in samples from fermentation by P. pentosaceus and I. orientalis in co-culture with either L. plantarum or L. brevis.

Microbiological and fermentation characteristics of togwa, a Tanzanian fermented food

Selected microbiological and metabolic characteristics of sorghum, maize, millet and maize-sorghum togwa were investigated during natural fermentation for 24 h. The process was predominated by lactic acid bacteria (LAB) and yeasts. The mesophiles, lactic acid bacteria, and yeasts increased and the Enterobacteriaceae decreased to undetectable levels within 24 h. The isolated microorganisms were tentatively identified as Lactobacillus plantarum, Lactobacillus brevis, Lactobacillus fermentum, Lactobacillus cellobiosus, Pediococcus pentosaceus, Weissella confusa, Issatchenkia orientalis, Saccharomyces cerevisiae, Candida pelliculosa and Candida tropicalis. The pH decreased from 5.24-5.52 to 3.10-3.34. Maltose increased initially and then decreased, fructose decreased and glucose levels increased during the first 12 h of fermentation. The organic acids detected during fermentation included DL-lactic, succinic, formic, pyruvic, citric, pyroglutamic and uric acid. Lactate was the predominant acid and increased significantly with time. The volatile organic compounds (VOC) detected included acetaldehyde, 2-methyl-propanal, 2-methyl-butanal, 3-methyl-butanal, ethanol, 2-methyl-1-propanol, 2-methyl-1-butanol, 3-methyl-1-butanol, diacetyl and acetoin. Ethanol was the predominant VOC and it increased significantly with time.

Isolation, characterisation and identification of lactic acid bacteria from bushera: a Ugandan traditional fermented beverage

One hundred and thirteen strains of lactic acid bacteria (LAB) were selected from 351 isolates from 15 samples of traditionally fermented household bushera from Uganda and also from laboratory-prepared bushera. Isolates were phenotypically characterised by their ability to ferment 49 carbohydrates using API 50 CHL kits and additional biochemical tests. Coliforms, yeasts and LAB were enumerated in bushera. The pH, volatile organic compounds and organic acids were also determined. The LAB counts in household bushera varied between 7.1 and 9.4 log cfu ml(-1). The coliform counts varied between < 1 and 5.2 log cfu ml(-1). The pH of bushera ranged from 3.7 to 4.5. Ethanol (max, 0.27%) was the major volatile organic compound while lactic acid (max, 0.52%) was identified as the dominant organic acid in household bushera. The initial numbers of LAB and coliforms in laboratory-fermented bushera were similar; however, the LAB numbers increased faster during the first 24 h. LAB counts increased from 5.5 to 9.0 log cfu ml(-1) during the laboratory fermentation. Coliform counts increased from 5.9 to 7.8 log cfu ml(-1) at 24 h, but after 48 h, counts were less 4 log cfu ml(-1). Yeasts increased from 4.3 to 7.7 log cfu ml(-1) at 48 h, but thereafter decreased slightly. The pH declined from 7.0 to around 4.0. Lactic acid and ethanol increased from zero to 0.75% and 0.20%, respectively. Lactic acid bacteria isolated from household bushera belonged to Lactobacillus, Streptococcus and Enterococcus genera. Tentatively, Lactobacillus isolates were identified as Lactobacillus plantarum, L. paracasei subsp. paracasei, L. fermentum, L. brevis and L. delbrueckii subsp. delbrueckii. Streptococcus thermophilus strains were also identified in household bushera. LAB isolated from bushera produced in the laboratory belonged to five genera (Lactococcus, Leuconostoc, Lactobacillus, Weissella and Enterococcus. Eight isolates were able to produce acid from starch and were identified as Lactococcus lactis subsp. lactis (four strains), Leuconostoc mesenteroides subsp. mesenteroides (one strain), Leuconostoc mesenteroides subsp. dextranicum (one strain), Weissella confusa (one strain) and L. plantarum (one strain).

New efficient amylase-producing strains of Lactobacillus plantarum and L. fermentum isolated from different Nigerian traditional fermented foods

Amylolytic lactic acid bacteria (ALAB) were isolated from Nigerian traditional fermented foods (fufu, burukutu, ogi-baba and kunu-zakki) with the aim of selecting efficient amylase-producing strains. Nine isolates were characterized on the basis of their phenotypic and taxo-molecular characteristics. Three groups could be distinguished by their fermentation profiles and this was confirmed by DNA restriction analysis. Though fermentation profiles gave good identification of strain K9 (unique representative of group III) as Lactobacillus fermentum, they could not be used to ascertain the taxonomic position of strains of groups I and II. Analysis of partial 16S rRNA sequences led to the identification of these groups as L. plantarum strains and confirmed the species of strain K9 as L. fermentum. The two distinct phenotypic groups of L. plantarum differed in their use of D-xylose, L-arabinose, melibiose and were different from the previously described amylolytic L. plantarum A6 isolated from retted cassava in Congo. L. fermentum K9 was different from L. fermentum OgiE1 and Mw2 isolated from Benin maize sourdough and it is the first amylolytic L. fermentum described from Nigerian fermented products. Enzymatic profiles showed some differences between the strains of a similar fermentation group. One of the most relevant characteristics of the isolates was a higher yield of amylase production than those reported for previously described ALAB grown under the same conditions. Furthermore, all isolates were tolerant to an exposure at pH 2 and to bile salts.

Contribution of starter culture to the sensory characteristics of fermented Almagro eggplants

Trial fermentations were performed using three experimental starter cultures with a view to selecting the most appropriate starter for use in the manufacture of Almagro eggplants. The lactic acid bacterial strains used in the starters had previously been isolated from spontaneous fermentations. The combined action of the obligate heterofermentative species Lactobacillus brevis and the facultative heterofermentative species L. plantarum yielded Almagro eggplants with sensory properties preferred by panelists. Conversely, another obligate heterofermentative species, namely, L. fermentum, present in certain starter formulations tested, appeared to encounter difficulty growing during fermentation and exerted little influence on the sensory characteristics of the eggplants produced.

Characteristics and significance of yeasts' involvement in cassava fermentation for 'fufu' production

Six different strains of yeast, namely Candida krusei, C. tropicalis, Pichia saitoi, Saccharomyces cerevisiae, P. anomala and Zygosaccharomyces bailii were found present in cassava-fermenting water in the early part of the fermentation. The latter part of the fermentation was dominated in all cases by three strains of yeast namely C. krusei, C. tropicalis and Z. bailii. All the yeast strains exhibited amylolytic capabilities while none was able to produce cellulase. All the strains except Zygosaccharomyces spp. exhibited polygalacturonase activity, but only C. krusei was able to produce linamarase. In a study on the inter-relationships between C. krusei and Lactobacillus plantarum, the growth of the yeast strain was not enhanced in cassava by the presence of the lactic acid bacteria, but the growth of the L. plantarum strain was significantly enhanced when co-inoculated with C. krusei.

Identification of lactic acid bacteria constituting the predominating microflora in an acid-fermented condiment (tempoyak) popular in Malaysia

Tempoyak is a traditional Malaysian fermented condiment made from the pulp of the durian fruit (Durio zibethinus). Salt is sometime added to proceed fermentation at ambient temperature. In various samples obtained from night markets, lactic acid bacteria (LAB) were the predominant microorganisms, ranging from log 8.4 to log 9.2 cfu g(-1). No other microorganisms were present to such a level. These samples contained reduced amount of saccharose, glucose and fructose but increased amount of D- and L-lactic acid and acetic acid compared with samples of non-fermented durian fruit. Sixty-four isolates of LAB were divided into five groups by use of a few phenotypic tests. A total of 38 strains of LAB were selected for comparison by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of their whole cell protein patterns with a SDS-PAGE database of LAB. These strains were also examined for their carbohydrate fermentation patterns by use of API 50 CH. Isolates belonging to the Lactobacillus plantarum group were shown to be the predominant members of the LAB flora. In addition, isolates belonging to the Lactobacillus brevis group, Leuconostoc mesenteroides, Lactobacillus mali, Lactobacilus fermentum and an unidentified Lactobacillus sp. were also observed. A high degree of diversity among isolates belonging to the Lb. plantarum group was demonstrated by analysis of their plasmid profiles.

Biochemical characterization of lactic acid bacteria isolated from spontaneous fermentation of 'Almagro' eggplants

A total of 149 strains of lactic acid bacteria isolated from the spontaneous fermentation of 'Almagro' eggplants were characterized and identified. Of the isolates, 148 were determined as belonging to the genus Lactobacillus. A coccoid, gram-positive database-negative isolate was obtained in the early stages of fermentation. The Lactobacillus strains were divided into six groups based on sugar fermentation patterns and other physiological and morphological characteristics, and were identified as Lactobacillus plantarum biotype 1 (54.4%), Lactobacillus brevis biotype 2 (19.5%), Lactobacillus fermentum (9.4%), Lactobacillus brevis biotype 3 (5.4%), Lactobacillus pentosus (4.7%) and nine strains, which were not included in the previous species, were grouped as Lactobacillus spp. (6.0%). Fermentation was initiated by Lactobacillus brevis biotype 2 and Lactobacillus fermentum. During the fermentation Lactobacillus plantarum became the predominant species.

Regulation of aspartokinase in Lactobacillus plantarum

As a rational approach to the genetic development of a stable lysine overproducing strain of Lactobacillus plantarum for the fermentation of 'ogi', a Nigerian fermented cereal porridge, regulation of lysine biosynthesis in this species was investigated. Spontaneous lysine overproducing mutants of Lact. plantarum were obtained and their aspartokinase activities compared with those of wild-type strains under different conditions. Results showed that aspartokinase activity of Lact. plantarum cell extracts was not inhibited by either lysine, threonine, methionine or combinations of lysine and threonine. Instead, methionine enhanced aspartokinase activity in vitro. Results indicated that lysine biosynthesis in Lact. plantarum could be regulated by lysine via the control of aspartokinase production in a way different to that described for other bacteria.

Phenotypically based taxonomy using API 50CH of lactobacilli from Nigerian ogi, and the occurrence of starch fermenting strains

One-hundred and twenty isolates of lactic acid bacteria isolated from ogi and three traditional cereal-based alcoholic beverages from Nigeria, together with 18 reference strains from Swedish sour doughs, and 50 type-and reference strains of mainly Lactobacillus, were phenotypically classified on their fermentation ability of 49 carbohydrates, including soluble starch. Data were examined by Jaccard Coefficient (SJ), Simple Matching Coefficient (SSM), and unweighted pair group algorithm with arithmetic averages (UPGMA). Seven major clusters were defined at the 82% SJ-similarity level (corresponds to the SSM-level of 91%). Three were identified as Lactobacillus plantarum or L. plantarum-like (together 41% of the ogi isolates). The others were obligately heterofermentative; Cluster 7 was identified as L. confusus (11% of the ogi isolates). Three minor clusters were identified as L. murinus, L. agilis or L. gallinarium, and Leuconostoc mesenteroides subsp. mesenteroides, respectively. The phenotype of the L. plantarum isolates varied within wide limits. Seventeen isolates possessed starch fermenting capacity. Nine of these were identified as L. plantarum or L. plantarum-like (isolated from ogi); one was identified as Leuconostoc mesenteroides subsp. mesenteroides, and the rest were unidentified non-clustering strains.

Characterization and frequency distribution of species of lactic acid bacteria involved in the processing of mawè, a fermented maize dough from Benin

Lactic acid bacteria involved in the natural fermentation of both home-produced and commercial mawè were investigated during a 72 h fermentation period. Lactobacillus spp. constitute the majority (94%) of the strains of the lactic acid bacteria isolated, among which 89% represent the Betabacterium group. They include L. fermentum (biotype cellobiosus) (41%), L. fermentum or L. reuteri (19%), L. brevis (26%), L. confusus (less than 2%), L. curvatus (less than 1%) and L. buchneri (less than 1%). Other isolated lactic acid bacteria were L. salivarius, Lactococcus lactis, Pediococcus pentosaceus, Pediococcus acidilactici and Leuconostoc mesenteroides. Several species were detected at the early stage of fermentation, but the final stage was dominated by L. fermentum (biotype cellobiosus) and L. fermentum or L. reuteri totalling 90% of the isolated strains. The trend was the same for both home-produced and commercial mawè. No strains of L. plantarum, generally reported as dominating lactic acid bacteria at the final stage of fermentation of most plant foods, were isolated.