Isolation and characterization of a protease-producing thermophilic bacterium from an African hot spring

The aim of this study was to screen for bacterial isolates from a hot spring in Eastern Zimbabwe (conditions in the hot spring: temperature 53 to 54°C and pH 9.3) for organisms of biotechnological interest. Screening of water samples from the hot spring resulted in the isolation of a novel bacterium with interesting protease activity. The bacterium was rod-shaped, Gram negative, motile, non-sporulating with 0.5 to 0.6 μM width and 2.0 to 4.0 μM length. It was oxidase and catalase positive and did not produce acid from glucose. The G+C content of the DNA was 71.7 mol%. A detailed examination of the isolate using conventional biochemical, physiological tests, fatty acid methyl ester analyses and 16S rDNA analysis showed that the strain code named EP1001 is a new genus within the γ-Proteobacteria that was distantly related to genera Stenotrophomonas, Xanthomonas, Xylella, and Lysobacter. The strain EP1001 produces an exoprotease enzyme when cultured in standard thermophilic M162 medium. The growth and protease production by the strain was also studied in shake flask cultivations to investigate optimum carbon and nitrogen sources. The results from physiological and biochemical characteristics, as well as fatty acids analysis, the 16S rDNA data and the chemotaxonomic data provided independent support for the novel nature of the isolate EP1001. In general, the results show that EP1001 isolate is a new bacterium in a new genus related to genera Stenotrophomonas, Xanthomonas, Xylella and Lysobacter, and has possibilities for use as a protease-producing bacterium.Keywords: γ-Proteobacteria, moderate thermophile, hot sprin

Probiotic properties of exopolysaccharide producing lactic acid bacteria isolated from vegetables and traditional Indian fermented foods

A total of 203 lactic acid bacteria (LAB) isolated from vegetables and traditional fermented food products of India such as idli batter, dhokla batter and dahi were screened for exopolysaccharide (EPS) production. Based on the amount of EPS produced, 17 LAB isolates were selected for biochemical and genetic characterization using 16S rRNA gene sequencing. The isolates were belonging to the genera Lactobacillus, Weissella and Pediococcus. In vitro examination was performed to evaluate their probiotic potential. Resistance to low pH and 0.3 % bile salts was studied. Bile salt hydrolase (BSH) activity, susceptibility to various antibiotics and antimicrobial activity against the non pathogenic E. coli K12 were also investigated. The results showed that the isolates could not grow in the presence of oxbile however some survived exposure to it for 2.5 h. Some isolates were able to grow in the presence of sodium taurocholate and showed considerable antimicrobial activity against E. coli K12. Five isolates were showing BSH activity which is reported for the genus Weissella for the first time. The results suggest that traditional fermented products could be an alternative and readily availabl

Effects of Pediococcus parvulus 2.6 and its exopolysaccharide on plasma cholesterol levels and inflammatory markers in mice

Intake of dietary fibres may reduce the prevalence of physiological risk factors of the metabolic syndrome, such as high plasma lipid levels and low-grade inflammatory state. Dietary fibres are usually of plant origin however microbial exopolysaccharides (EPSs) have analogue structures that could potentially exert similar physiological effects. Pediococcus parvulus 2.6 (Pd 2.6) excretes a ropy EPS and has previously shown probiotic potential. The aim of this work was to evaluate physiological effects of Pd 2.6 and its EPS in vivo. The live Pd 2.6 (both the ropy and non-ropy isogenic variant) and its purified EPS were fed to hypercholesterolemic LDL-receptor deficient mice for 6 weeks to investigate their effects on cholesterol levels and the inflammatory tone of the animals. Both variants of Pd 2.6 survived passage through the mouse gut fulfilling an important criterion of probiotics. The ability to produce EPS was conferring an advantage to survival (faecal recovery of 3.7 (1.9-8.7) vs. 0.21 (0.14-0.34) *108 CFU, P < 0.001, median and 25th and 75th percentiles). The ropy Pd 2.6 decreased the levels of soluble vascular cell adhesion molecule-1 compared to the EPS alone (591 ± 14 vs. 646 ± 13 ng/ml, P < 0.05). An increase in liver weight in mice fed the purified EPS was observed, but with no change in liver lipids. No changes in blood lipids were detected in any group. Further the EPS induced growth of the caecal tissue and increased the amount of caecal content showing bulking properties like that of a dietary fibre

Substrate Control in Fed-Batch Cultivations Using a Model-Based Modification of a PI-Controller

A fedbatch process shows exponential growth under ideal conditions. To obtain good substrate concentration control it is necessary that the regulator can track an exponentially growing feed demand, and standard PI-control has to be supplemented with an estimated basic dosage to get reasonable control. However, an exponentially growing concentration error is impossible to avoid. An I-term could be interpreted as an observer of a constant demand, and we have proposed to replace it with a model-based observer for an exponentially growing demand. In the resulting controller the integrator is replaced by an unstable pole at s = μ, the specific growth rate, and the initial condition of this term is equivalent to the basic dosage part. The regulator can now track the exponentially growing feed demand without error. Pseudomonas cepacia was grown on salicylate as sole carbon and energy source. Salicylate is a toxic substrate, so it is important to have good substrate control. On-line measurement of salicylate concentration was carried out using a filtration system from which cell-free permeate was passed to a flow-through spectrophotometer. Introducing more instability into the controller requires attention to the anti-windup features. No such problems were found during the cultivations or in simulations of the effect of conceivable disturbances like pump-failure, air-bubbles in the spectrofotometer, and low oxygen concentration induced growth-rate reduction

Nitrogen and Phosphorus Removal from Urine by Sequential Struvite Formation and Recycling Process

Recovering nutrients from urine as solid minerals such as struvite can eliminate many hurdles related to the use of liquid urine as fertilizer in the current urine separation systems. The focus of this study has been to increase nitrogen and phosphorus removal efficiencies by developing a struvite formation and recycling process. Struvite crystallization was carried out in urine samples by addition of MgO where 92% of phosphorus as orthophosphate was recovered. In order to optimize the use of calcined struvite in the struvite recycling step, four calcination treatments were tested and calcination at 200 degrees C for 3 h was chosen for further experiments. To remove the remaining ammonia present in urine a struvite recycling step was used subsequently. Through sequential struvite formation and struvite recycling process up to 90% of ammonium nitrogen was successfully removed

Oxygen supply to immobilized cells : 2. Studies on a coimmobilized algae-bacteria preparation with in situ oxygen generation

A coimmobilized mixed culture of algae, Chlorella pyrenoidosa, and bacteria, Gluconobacter oxydans, has been studied. The conversion of glycerol to dihydroxyacetone(1,3-dihydroxy-2-propanone), catalysed by the bacteria, was used to indicate the oxygen supply in the immobilized preparation. The oxygen produced by the algae in the coimmobilized preparation was used by the bacteria more effectively than when the cells were immobilized separately and mixed within the reactor. A preparation consisting of only bacteria and no algae was much less effective. The coimmobilized preparation was used in the continuous production of dihydroxyacetone for six days without any significant loss of activity