A.I. Sanni

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.

The need for process optimization of African fermented foods and beverages

Many papers have been published on various aspects of African fermented foods and beverages. The emphasis has been on the microorganisms used, and the nutritional status of the products after fermentation. The preparation of these products is still a traditional family art and the fermentation process is by uncontrolled inoculation. This has led to variations in the quality and stability of the products. Research efforts in this field are still based on old recipes transmitted from generation to generation due to the fact that the consumers are not easily influenced by innovations, and the apparent lack of biotechnological background. This paper gives a brief account of the fermentation process of some of the fermented products to show the varied pattern of the microbiology. The unpredictability of the complex microflora implicated in the fermentations, and the lack of adequate knowledge of the associated microbes are discussed. The paper suggests a number of steps to be taken to optimize the fermentation process as a means of maintaining the peculiar characteristics of each product and establishment of small-scale industrial production.

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.

Yeasts in the traditional brewing of pito in Ghana

Yeasts from pito, a cereal-based traditional alcoholic beverage were isolated and characterized using biochemical and physiological tests. A total of 21 strains belonging to 8 genera were identified as Saccharomyces cerevisiae (8), Candida tropicalis (4), Kloeckera apiculata (2), Hansenula anomala (2), Torulaspora delbrueckii (3), Schizosaccharomyces pombe (1) and Kluvyeromyces africanus (1). Various diluents used for a 2 h holding period shows that 0.1% malt extract and peptone gave 20% decrease in cell viability for all the isolates, while phosphate buffer least supported the survival of the yeast cells with about 90% decrease in cell viability obtained for S. pombe at the end of the 2 h holding period. The effect of pH and temperature on the growth of the isolates revealed that at relatively low temperatures, growth increased with increasing pH, but a decrease was observed with increasing pH at high temperatures for S. cerevisiae and Candida tropicalis. All the isolates demonstrated good growth (102 to 106 c.f.u./ml) at 10% ethanol concentration over a period of 8 days incubation. However, growth of K. africanus was completely inhibited after 4 days incubation period. The quality indices of the beverage produced using S. cerevisiae as a single-starter organism compared favourably with the traditional brew. The paper suggests ways of scientifically regulating the production of fermented foods in sub-Saharan Africa.

Biochemical composition of infant weaning food fabricated from fermented blends of cereal and soybean

Abstract Infant weaning foods were produced from fermented blends of germinated and ungerminated cereal–soybean flour paste, using Saccharomyces cerevisiae and L. plantarum ATCC 10776 as starter cultures. A shorter fermentation period of less than 24 h was obtained compared to the traditional 72–96 h. Protein content of the formulated blends increased with fermentation, ranging from 15.5% in F25B to 18.2% in F410B. This could be attributed to the breakdown of nutrients of the substrates especially soybean, by the starter organisms. The relative decrease in the calcium and phosphorus content of the fermented blends could have resulted from leaching during the steeping stage and subsequent loss from the discarded pomace of the grains which contained most of the minerals. Fermentation also provided optimal pH for the degradation of the phytate phosphorus constituents of the formulated blends. The observed increase in the riboflavin, thiamine, niacin, ascorbic acid and some of the amino acids of the fermented blends could be due to the metabolic activities of the fermenting microorganisms. Porridges made from all the formulated cereal-soybean blends were rated above average in terms of overall acceptability, but F15B had the highest preference rating. ©

Functional properties of selected starter cultures for sour maize bread

This paper focuses on the functional properties of maize sour-dough microflora selected and tested for their use as starter cultures for sour maize bread. Lactic acid bacteria and yeasts isolated from spontaneously fermented maize dough were selected based on dominance during fermentation and presence at the end of fermentation. Functional properties examined included acidification, leavening and production of some antimicrobial compounds in the fermenting matrix. The organisms previously identified as Lactobacillus plantarum, Lb. brevis, Lb. fermentum, Lb. acidophilus, Pediococcus acidilactici, Leuconostoc mesenteroides and Leuconostoc dextranicum and Saccharomyces cerevisiae were used singly and as mixed cultures in the fermentation (fermentation time: 12h at 28+/-2 degrees C) of maize meal (particle size >0.2mm). The pH fell from an initial value of 5.62-3.05 in maize meals fermented with Lb. plantarum; 4.37 in L. dextranicum+S. cerevisiae compared with the value for the control (no starter) of 4.54. Significant differences (P <or =0.05) were observed in values obtained for the functional properties tested when starters were inoculated compared with the control (no starter) except for leavening. Bivariate correlations at 0.01 levels (two-tailed) showed that significant correlations existed among pH and production of antimicrobial compounds in the fermenting meals, the highest correlation being between production of diacetyl and acid (0.694), a positive correlation indicating that production of both antimicrobial compounds increase together with time. Antimicrobial activities of the fermented maize dough were confirmed by their abilities to inhibit the growth of Salmonella typhi, Escherichia coli, Staphylococcus aureus and Aspergillus flavus from an initial inoculum concentration of 7 log cfu ml(-1)) for test bacteria and zone of inhibition of up to 1.33 cm for aflatoxigenic A. flavus. The findings of this study form a database for further studies on the development of starter cultures for sour maize bread production as an alternative bread specialty.

Amplification of 1-amino-cyclopropane-1-carboxylic (ACC) deaminase from plant growth promoting rhizobacteria in Striga-infested soil

Experiments were conducted in pots to determine the growth effect of different rhizobacteria on maize under Striga hermonthica infestation. Three bacteria were selected based on their plant growth promoting effects. Whole bacterial cells of the rhizobacteria were used to amplify 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase gene by polymerase chain reaction (PCR). Each bacterial inoculation increased agronomic characteristics of maize although not always to a statistically significant extent. The extent of growth enhancement differs between the isolates. Enterobacter sakazakii 8MR5 had the ability to stimulate plant growth, however in the PCR study, ACC deaminase was not amplified from this isolate, indicating that not all plant growth-promoting rhizobacteria contain the enzyme ACC deaminase. In contrast, an ACC deaminase specific product was amplified from Pseudomonas sp. 4MKS8 and Klebsiella oxytoca 10MKR7. This is the first report of ACC deaminase in K. oxytoca.

Antagonistic activity of bacteriocin produced by Lactobacillus species from ogi, an indigenous fermented food.

Seven Lactobacillus species each with one or more strains were isolated from various fermented cereal gruels (ogi). They were identified as L. plantarum (3 strains), L. delbrueckii (1 strain), L. brevis (2 strains), L. reuteri (2 strains), L. casei (1 strain), L. fermentum (1 strain) and L. acidophilus (1 strain). Bacteriocin production was observed in cell‐free supernatants of 8 of these strains with L. fermentum, L. delbrueckii and L. reuteri strains (white maize ogi) being negative. The bacteriocin produced by the eight strains inhibited the growth of various target organisms with the inhibition strongly noticed using Enterococcus faecalis as indicator. While catalase treatment, pH changes and heat treatment up to 80 °C had no effect on the activity of bacteriocin from these isolates, treatment with trypsin and proteinase K resulted in complete loss of inhibitory activity of the bacteriocins. A reduction in the inhibitory activity of the bacteriocins was also found to occur with increasing concentrations of glucose or peptone in the cultivation medium.

Technological properties and probiotic potential of Enterococcus faecium strains isolated from cow milk

To identify enterococci from the fermentation of milk for the production of nono, an African fermented dairy product, to determine the technological properties for suitability as starter cultures and safety as probiotics.

Microbial deterioration of traditional alcoholic beverages in Nigeria

Abstract A study was carried out to investigate the microbiological quality and physico-chemical changes of “aged’’ cereal-based traditional alcoholic beverages in Nigeria. There were variations in the microorganisms isolated from sekete, pito and burukutu at post-production time of 72 h, but Saccharomyces cerevisiae, Acetobacter aceti, A. hansenii, A. pasteurianus, Alcaligenes, Flavobacterium, Lactobacillus plantarum and L. brevis were common to all samples. A vinegary flavour and off-odour were the pronounced characteristics of the deteriorating beverages. The decrease in the ethanol from 3% in the fresh product to 1% at the end of 72 h retailing period is proportional to the acetic acid content of the drinks. However, slight decreases were observed for lactic, malic, succinic and formic acid constituents of the beverages. Although no enterobacteriaceae was isolated, some of the identified isolates are potentially pathogenic, and can become injurious to the health of the consumers of “aged’’ batches of the beverages.