The Influence of Agitation Rates, pH and Calcium Carbonate on L-lysine Production by Bacillus subtilis using Agricultural Products as Carbon and Nitrogen Sources

L-Lysine is an essential amino acid that is required in the diet of humans and animals. It is utilized in human medicine, cosmetics and pharmaceutical industry. ’The influence of agitation rates, pH and calcium carbonate on L-lysine production by Bacillus subtilis using agricultural products as carbon and nitrogen sources was studied. The L-lysine-producing bacteria had already been isolated from Nigerian soil. They were purified and Identified as B. subtilis PR13 and B. subtilis PR9, using cultural, biochemical and molecular characteristics. Optimization of some parameters which included agitation rates, pH values and CaCO3 concentrations, on L-lysine production by the Bacillus species was carried out. The L-lysine was produced in 250 ml flasks containing fermentation media (FM1 and FM2). The findings revealed that, enhanced L-lysine yield of 2.10 and 1.33 mg/ml was observed at agitation rate of 180 rpm for B. subtilis PR13 and PR9 respectively. There was a positive correlation between agitation rates and L- lysine production by B. subtilis PR13 and PR9 (r = 0.96 and 0.83 respectively). The pH of 7.5, stimulated optimum L- lysine yield of 2.27 mg/ml for PR13 and 1.38 mg/ml for PR9. There was a positive correlation between pH values and L-lysine production by B. subtilis PR13 and PR 9 (r = 0.63 and 0.50 respectively). The supplementation of 40g/l of CaCO3, enhanced optimum L-lysine yield of 2.18 mg/ml for B. subtilis PR 13 and 1.30 mg/ml for B. subtilis PR9. There was a positive correlation between varying concentrations of calcium carbonate and L-lysine production by the B. subtilis PR13 (r =0.35), while negative correlation was observed for B. subtilis PR 9 (r = -0.10). The results obtained in the study illustrated that the optimization of process parameters could increase the L-lysine yield from agricultural products by B. subtilis PR13 and B. subtilis PR9.

Yield and rheological properties of exopolysaccharide from a local isolate: Xanthomonas axonopodis pv. vesicatoria

Background: The aim of the present study was to evaluate gum productivity of a local strain, Xanthomonas axonopodis pv. vesicatoria, isolated from pepper plant, and its rheological behavior for the first time compared to the standard strain, Xanthomonas campestris DSM 19000 (NRRL B-1459). The influence of operational conditions (agitation rate and inoculum volume) on gum production and rheological properties of gums from the Xanthomonas strains were investigated. Results: The isolated strain of Xanthomonas showed similar xanthan yield compared to the standard strain. Furthermore, this study clearly confirmed that gum yield depended on bacterial strain, agitation rate, and inoculum size. The most suitable conditions for the gum production in an orbital shaker in terms of agitation rate and inoculum size were 180 rpm and 5%, respectively, resulting in an average production of 10.96 and 11.19 g/L for X. axonopodis pv.vesicatoria and X. campestris DSM 19000, respectively. Regarding the rheological properties, Ostwald-de-Waele and power law models were used to describe flow and oscillatory behavior of the gum solutions, respectively. Consistency of the novel gum solution remarkably was much higher than the commercial xanthan gum solution. Flow and oscillatory behavior and their temperature ramps showed that weak gel-like structure could be obtained with less gum concentrations when the novel gum was used. Conclusion: Therefore, yield and technological properties of the aqueous solutions of the exopolysaccharide synthesized by X. axonopodis pv. vesicatoria were observed to be more suitable for industrial production.

Control de las tasas de aireación y agitación en la producción de surfactina en un cultivo alimentado (fed-batch) en espuma desbordante con fermentación industrial / Control of agitation and aeration rates in the production of surfactin in foam overflowing fed-batch culture with industrial fermentation

Bacillus amyloliquefaciens fmb50 produces a high yield of surfactin, a lipopeptide-type biosurfactant that has been widely studied and has potential applications in many fields. A foam overflowing culture has been successfully used in the combined production-enrichment fermentation of surfactin. In this study, the agitation and aeration rates were found to have relationships with foam formation and surfactin enrichment. A maximum surfactin concentration of 4.7 g/l of foam was obtained after 21 h of culture with an agitation rate of 150 rpm and an aeration rate of 1 vvm in fed-batch culture. By controlling the foam overflow rate (f out) of a fed-batch culture, surfactin concentration in the foam was continuously maintained above 4 g/l.

Bacillus amyloliquefaciens fmb50 produce gran cantidad de surfactina, un biosurfactante de tipo lipopeptídico que ha sido objeto de estudios pormenorizados y tiene aplicaciones en muchos campos. El cultivo en espuma desbordante se ha utilizado con éxito en la fermentación combinada de producción-enriquecimiento de surfactina. En este estudio, se halló que las tasas de aireación y agitación tienen relación con la formación de espuma y el enriquecimiento de la surfactina. Se obtuvo una concentración máxima de surfactina de 4,7 g/l de espuma después de 21 h de cultivo con una tasa de agitación de 150 rpm y una tasa de aireación de 1 vvm en un cultivo alimentado (fed-batch). Al controlar la tasa de espuma desbordante (f out) de un cultivo fed-batch, la concentración de surfactina en la espuma se mantuvo continua por encima de 4 g/l.

Oxygen limitation favors the production of protein with antimicrobial activity in Pseudoalteromonas sp

This study examined the effect of dissolved oxygen concentration on the production of biomass and metabolites with antimicrobial activity of Pseudoalteromonas sp cultured at 0, 150, 250, or 450 revolutions per minute (rev. min-1). Dissolved oxygen (D.O) was monitored during the fermentation process, biomass was quantified by dry weight, and antimicrobial activity was assessed using the disk diffusion method. The bacterium Pseudoalteromonas reached similar concentration of biomass under all experimental agitation conditions, whereas antimicrobial activity was detected at 0 and 150 rev. min-1 registering 0% and 12% of D.O respectively corresponding to microaerophilic conditions. Antibiotic activity was severely diminished when D.O was above 20% of saturation; this corresponded to 250 or 450 rev. min-1. SDS-PAGE electrophoresis revealed a protein with a molecular weight of approximately 80 kilodaltons (kDa) with antimicrobial activity. Pseudoalteromonas is capable of growing under oxic and microaerophilic conditions but the metabolites with antimicrobial activity are induced under microaerophilic conditions. The current opinion is that Pseudoalteromonas are aerobic organisms; we provide additional information on the amount of dissolved oxygen during the fermentation process and its effect on antimicrobial activity.