食品および産業微生物学ジャーナル

Objective: The objective of this study was to isolate, identify and characterize the lactic acid bacteria (LAB) from a domestic food (Chakka) and to evaluate their properties for application as starter cultures in fermented dairy products.
Methods: LAB were isolated using standard MRS/M17 media and characterized phenotypically and identified by 16SrDNA sequencing and Whole Genome Sequencing and their evolutionary relationships were plotted using MEGA X. Culture conditions were optimized in a shaker incubator and different media formulations using Skimmed Milk Powder, Yeast Extract, Glucose, and Casein Enzyme Hydrolysate were designed and tested. Subsequently, the isolates were grown in a 1 L bioreactor under controlled conditions to study their total viable count and the growth rates. Lactic acid production was quantified in MRS and laboratory formulated M2 media under optimized growth conditions. The recovery, quantification and total yield of exopolysaccharides (EPS) produced by the isolated strains was also done.
Results: The isolates were grouped as bacilli (C2, C4, C5, C12, and P1) and cocci(Q1, and Q2). The bacilli were identified as subspecies of Lactobacillus delbrueckii and cocci were identified as Streptococcus thermophilus. M2 media was found to be a viable alternative to standard media. Bacilli and cocci were found to produce L and D-lactic acid, respectively, and bacilli were better lactic acid producers than cocci. Similarly, bacilli were found to be better EPS producers in M2 media.
Conclusion: The results suggest of this study suggest that strains isolated from Chakka could be potential starter cultures for use in yogurt manufacturing. The critical understanding about the metabolism of these LAB would be helpful for the maintenance of strains and their exploitation as starter cultures.

Fungal infection and aflatoxin contamination were evaluated on smoked or dried fishes sold in surrounding markets of Cotonou. These fishes are traditionally processed to avoid losses and rapid perishability and preserve them from a longer period. Fungal contamination was evaluated after plating on selective media with a total of 175 fungal isolated from 56 samples. Fungi identification shown high prevalence of Aspergillus genus that represent 44, 56% followed by Mucors (30%), Rhizopus and Rhizomucor (9.14%; 5.14%, respectively), Penicillum sp. (6.85%) and another minority. In Aspergillus genus, A. flavus represented 29.48% after A. niger that was 37.17%. A. parasiticus, A. fumigatus, A. wentii, A.clavatus and A. ochraceus had 10.25%, 7.69%, 5.12%, 3.84% and 2.56% respectively followed by A. tamarii, A. candidus and A. versicolor that had 1.28% each. In aflatoxin pathway gene cluster, we investigated three specific genes AflD, AflO and AflP to 18 stumps of A. flavus isolated. This shows that there are potential aflatoxins producers which were suspected by their fluorescence on CCA medium at visible UV and confirmed by determination in chloroformic extract by HPLC. TLC results of chloroformic extracts of samples confirmed the presence of AFB1 in some samples. This is the first study that shows mycotoxigenic fungi and mycotoxins in traditionally processed fishes sampled from Cotonou markets in Benin.

The microbial ratio of the bulk yoghurt starter cultures determines the strength of proto cooperation among the lactic acid bacteria which can build up the proper chemical and physical structure of the yoghurt and control the post-acidification effect. Therefore, this attempt is to find out the best microbial ratio of the yoghurt starter culture which can produce good quality yoghurts and control post acidification. The isolated L. bulgaricus and S. thermophilus strains from bulk cultures were used to prepare new starter cultures by changing L. bulgaricus, S. thermophilus ratios as 1:1, 1:1.5 and 1.5:1 and then S.thermophilus and L.bulgaricus growth pattern during the yoghurt incubation period was determined and compared that with the typical lactic acid fermentation growth curve. Then each culture added yoghurt sample was stored under the cooling conditions for 15 days and then checked pH, acidity like chemical changes, physical changes of the yoghurt and sensory properties to select the best microbial ratio. The results revealed when L. bulgaricus and S. thermophilus ratio was 1:1, their growth patterns are similar to the typical lactic acid growth curve as two exponential phases separated from stationery phase which reveals the efficient proto cooperation among two bacteria and higher metabolic potentials of them which is able to release metabolites into the fermenting medium in right time to develop standard yoghurt qualities as texture, color, taste and pH. Furthermore, the results revealed end of the 15 days pH of yoghurt was 4.4 which are suitable to maintain the good quality of yoghurt with high shelf life. But when L. bulgaricus population is high in the yoghurt starter culture, post acidification was high, and it deforms the yoghurt structure due to syneresis.And, when S. thermophilus population is high in the yoghurt starter culture, sensory qualities of the yoghurt were not up to the standards.

Food safety have become topical across the globe, especially in developing countries owing to an increase in street food vendors and the non-enforcement of laws governing establishment and operation of food vendors. This research determined the microbiological quality of soups served with “tuo-zaafi” marketed in the Central Business District of the Tamale Metropolis. A total of 30 samples were collected, preserved, transported and analysed in the Spanish Laboratory of the University for Development Studies. The presence, levels and antibiotics resistivity of bacteria in soup samples were determined. Staphylococcus aureus recorded the highest (83.3%) in soup sample with levels ranging from 0 to 9.2 × 104 cfu/ml. E. coli was detected in 76.7% of the soup with levels varying from 0 to 8 × 104 cfu/ml and Salmonella spp. (63.3%) levels ranged from 0 to 9.6 × 104 cfu/ml. Shigella spp. was present in 73.3% of samples with levels ranging from 0 to 9.5 × 104 cfu/ml. Mean microbial counts in “Ayoyo” and Dry Okra soups across the study area were 1.19 × 104 cfu/ml and 1.83 × 104 cfu/ml, respectively. Contamination varied significantly (p<0.001). E. coli, Salmonella spp. and Shigella spp. were more resistant to antibiotics whiles Staphylococcus aureus was more susceptible. The study revealed that soups served with “tuo-zaafi” sold on the street in the Business District of Tamale were unsatisfactory and unsafe for consumption and posed a potential health hazard to consumers. The contamination was attributed to improper hygiene, handling and environmental conditions. The Food and Drugs Authority should strictly impose laws and ensure compliance to food safety measures.

Lactic acid (LA) is a commodity chemical used in pharmaceuticals, bio plastics, and food, home and personal care products. It is commercially produced by fermentation of corn starch, which requires large amounts of land and water. Almond hulls are a cheap agricultural byproduct that have high sugar content and could be used as a carbon source in the fermentation of lactic acid. In this study, we fermented almond hulls using a mixed culture from primary sludge and a mono-culture from Lactobacillus rhamnosus and compared the production of lactic acid from almond hulls against that of other alternative feedstocks. Other feedstocks tested included corn stover and pine wood as lignocellulosic feedstocks, food waste, glucose, glycerol as a cheap chemical byproduct and sorbitol as a negative control. In both mixed culture and pure culture, almond hulls (maximum values for yield 0.55 g/g biomass, productivity 2.8 g/L/h, >99% L-LA) gave higher yields than food waste (maximum values for yield=0.44 g/g biomass, productivity=1.2 g/L/h, 84-95% L-LA), but lower yields than glucose (maximum values for yield 0.95 g/g biomass productivity 4.2 g/L/h, ≥ 96% L-LA). Pine wood and corn stover did not produce lactic acid efficiently under the mixed culture conditions tested. The results of this study lend support for the use of almond hulls as an affordable feedstock for the production of lactic acid.