Propionibacterium microaerophilum sp. nov., a microaerophilic bacterium isolated from olive mill wastewater.

A new gram-positive, facultative anaerobic, microaerophilic bacterium, designated strain M5T, was isolated from a decantation reservoir of olive mill wastewater. The cells were rod-shaped, non-motile, non-spore-forming and catalase-negative. Growth occurred at pH ranging from 4.5 to 9.5, with optimum growth at 7.0. The optimum temperature for growth was around 30 degrees C. Although growth occurred under anaerobic and aerobic conditions, the optimum O2 concentration for growth was determined as 5% in the gas phase of the culture. During anaerobic growth, glucose or lactate were mainly fermented to propionate, acetate and CO2. In the presence of O2 (more than 2%), glucose was oxidized completely to CO2. The G+C content of the DNA was 67.7+/-0.6 mol% and 16S rRNA gene analysis revealed that the new isolate belonged to the cluster of 'dairy' propionibacteria, Propionibacterium acidipropionici being its closest phylogenic relative (97.5% similarity). However, the level of DNA relatedness between strain M5T and P. acidipropionici was 56.2%. Consequently, both the phenotypic (range of substrates used) and genotypic characteristics of strain M5T allow it to be assigned as a new species of the genus Propionibacterium, Propionibacterium microaerophilum sp. nov. The type strain is strain M5T (= CNCM I-2360T = DSM 13435T).

Effect of organic complex compounds on Bacillus thermoamylovorans growth and glucose fermentation.

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.

Effect of pH on Bacillus thermoamylovorans Growth and Glucose Fermentation.

The effect of pH on the growth and physiology of Bacillus thermoamylovorans, a new moderately thermophilic and non-spore-forming bacterium isolated from palm wine, was studied. Growth occurred from pH 5.4 to 8.5, with optimum growth at 7.0. During the exponential growth phase at optimum pH, glucose was consumed at the maximum rate (qs), 17.87 mmol g(sup-1) h(sup-1), and was mainly fermented into acetate, ethanol, and formate (76.5% of metabolites produced). In acidic or alkaline conditions, glucose specific consumption rates were considerably reduced (qs = 8.06 mmol g(sup-1) h(sup-1) at pH 5.6 and 2.85 mmol g(sup-1) h(sup-1) at pH 8.4), and a switch in glucose metabolism toward lactate production (62.6% of metabolites produced at pH 5.6 and 41.2% of those produced at pH 8.4) was observed. Moreover, optimum cellular yield (Y(infx/ATP)), 14.8 g mol(sup-1), and optimum energy yield (Y(infATP/s)), 2.65 mol mol(sup-1), were observed at neutrality. The results of this study were compared with published data about lactic acid bacteria; this comparison allowed us to complement our previous taxonomic study of B. thermoamylovorans and to identify additional phenotypic differences between B. thermoamylovorans and lactobacilli.

Bacillus thermoamylovorans sp. nov., a moderately thermophilic and amylolytic bacterium.

A moderately thermophilic, facultatively anaerobic, amylolytic bacterium was isolated from palm wine, a tropical alcoholic beverage that was sampled in Senegal. The cells were gram positive, catalase positive, non-spore forming, rod shaped, and slightly motile with peritrichous flagella. The strain which we examined did not possess cytochrome and produced L-(+)-lactate, acetate, ethanol, and formate but not hydrogen during carbohydrate fermentation. Growth occurred at pH values ranging from 5.4 to 8.5, and optimum growth occurred at around pH 7.0. The optimum temperature for growth was around 50 degrees C, and the upper temperature limit for growth was 58 degrees C. The guanine-plus-cytosine content of the DNA was 38.8 +/- 0.2 mol%. A sequence analysis of the 16S rRNA gene revealed that the new organism is closely related phylogenetically to members of genus Bacillus. Despite the lack of spores, we propose that on the basis of phylogenetic characteristics, the new isolate should be classified as a new Bacillus species, Bacillus thermoamylovorans. The type strain is strain DKP (= Collection of Institut Pasteur CNCM I-1378).