The microflora of a Sudanese sorghum flour, a spontaneously fermented sourdough and along‐term sourdough produced in a Sudanese household by consecutive re‐inoculations, wasstudied. The dominant contaminants of sorghum flour were Gram‐negative, catalase‐positive,rod‐shaped bacteria with counts of about 105 cfu g−1. Thespontaneously fermented sorghum sourdough showed a bacterial succession from Gram‐negative,catalase‐positive contaminants to Enterococcus faecalis, Lactococcus lactis,Lactobacillus fermentum and Lact. reuteri. The total bacterial countreached about1010 cfu g−1 and the pH dropped from6·4 to 3·35 in about 42 h. In this phase, only the latter two species remaineddominant in a ratio of 1:1. From the Sudanese long‐term dough, seven strains of Lactobacillus were isolated, representing the dominant flora. Sequence comparison ofpartial 16S rRNA gene sequences were used to clarify their phylogenetic positions. Five strainswere classified as Lact.vaginalis and could be regarded as heterogenous biovars of thisspecies. The other two strains could be assigned to Lact.helveticus.RAPD‐PCR and sugar fermentation patterns were useful in differentiation of these strains.

In the present work, the treatment of synthetic waters doped with iron (II) has been studied. The treatment mechanism used in this study is the biological oxidation which consists, in test tubes, of bringing bacteria isolated on Petri dishes into contact with water containing divalent iron (II). These de-ironing bacteria (non-specific bacteria) are used to carry out laboratory biological oxidation experiments on iron (II) under different pH conditions (pH = 3.4-3.6, pH = 7.3-7.5 and pH = 9.8-10) and variable concentration of iron (II). Biological treatment trials included different concentrations of iron during time intervals of a day. Examination of the elimination kinetics of Iron (II) indicates a removal rate of 59.453% for an initial iron concentration in the synthetic solution of 1 mg•L −1 at basic pH (pH = 9.8-10). Therefore, the degradation of divalent iron by this method seems to be quite effective, but it should be noted that biological nitrification is impaired by the presence of high iron concentrations above 5 mg•L −1 .

The effect of the concentration of a mixture (1/1 [wt/wt]) of yeast extract and bioTrypcase (YE+bT) on the growth and physiology of a new species, Bacillus thermoamylovorans, a moderately thermophilic, non-spore-forming, lactic acid-producing bacterium isolated from palm wine, was studied. At an initial glucose concentration of 100 mM, B. thermoamylovorans growth was limited when the concentration of YE+bT was lower than 5.0 g liter−1; under these conditions, cellular yield reached a maximum value of 0.4 g of cells per g of YE+bT. Growth limitation due to deficiency in growth factors led to a significant shift in glucose metabolism towards lactate production. Lactate constituted 27.5 and 76% of the end products of glucose fermentation in media containing YE+bT at 20.0 and 1.0 g liter−1, respectively. This result markedly differed from published data for lactic bacteria, which indicated that fermentative metabolism remained homolactic regardless of the concentration of YE. Our results showed that the ratio between cellular synthesis and energy production increased with the concentration of YE+bT in the culture medium. They indicate that the industrial production of lactic acid through glucose fermentation by B. thermoamylovorans can be optimized by using a medium where glucose is present in excess and the organic additives are limiting.

Food preservation is a big challenge for the industries. The mechanisms of preservation involved microorganisms such as lactic acid bacteria. Modeling the microorganisms growth is a very useful information to well-understand their behavior and to propose the best conditions for food preservation. In this way, this study was to propose a mathematical model of the dynamical growth of Lactococcus lactis CWBI-B1410 which play a main role for the bio-conservation of fish. This study is conducted by varying the concentration of glucose and nitrogenized matter. The results showed that the mathematical model predicted the growth of L. lactis CWBI-B1410. The curves that are predicted are exactly those that can be observed experimentally. The results showed that the production of biomass by L. lactis CWBI-B1410 is obtained on the MRS medium composed of 15 g of glucose per liter and 40 g of nitrogenous material per liter. From the obtained results, it could be clearly advocated that for two tests with the same amount of nitrogenous matter, it is possible to achieve economies of scale in glucose while maintaining the same biomass performance.