Antimicrobial activity of camwood (Baphia nitida) dyes on common human pathogens

Antimicrobial activity of four aqueous extracts of camwood dyes obtained from different locations in Nigeria were investigated by agar diffusion, disc diffusion and agar dilution method against five clinical isolates obtained from inpatient attending the University of Port Harcourt Teaching Hospital. The isolates were Staphylococcus aureus, Escherichia coli, Bacillus cereus, Proteus vulgaris and Pseudomonas aeruginosa. Broad spectrum activity revealed B. cereus and S. aureus as more susceptible with zones of inhibition ranging from 5.4 to 19.2 mm, while, E. coli, P. vulgaris and P. aeruginosa were the least susceptible at an inhibition zone ranging from 0.8 to 15.6 mm. Results show that the extracts exhibited inhibitory activity against the test organisms at a minimum inhibitory concentration (MIC) of 37.5 mg/ml. Phytochemical screening revealed the presence of flavonoid and a trace of alkaloids. These results show that camwood dye possessed significant antimicrobial activity and hence can be used as a remedy for pathogenic infections.Key words: Antimicrobial activity, camwood extract, Nigeria, pathogenic microorganisms, zone of inhibition

Enhancement of Heterotrophic Biomass Production by Micractinium sp. ME05

In this study, heterotrophic growth conditions for Micractinium sp. ME05 cells were investigated for the improvement of biomass production. Plackett Burman (PB) method was used to screen process variables, namely, pH, carbon source and yeast extract concentrations, temperature and inoculum ratio, that affect the biomass production. The Box-Behnken (BB) design of response surface methodology (RSM) was applied to evaluate the interaction effect of process variables and to optimize them. The biomass obtained from PB design was 1.07 g/L and pH, temperature and carbon source concentration were selected based on their positive effect on biomass production. Applying response optimizer tool of RSM, the highest biomass obtained was 2.08 g/L. The results revealed that a 1.9-fold increase in biomass concentration was achieved by manipulating cultivation conditions which would be valuable for large scale cost efficient industrial applications of biomass production

Culture systems incorporating heterotrophic metabolism for biodiesel oil production by microalgae

The feasibility of using various culture systems incorporating heterotrophic metabolism for biodiesel oil production was compared. Heterotrophic culture can be used to achieve high cell concentration, and depending on the strain and organic carbon source employed, the introduction of light (mixotrophic culture) can enhance cell growth and oil accumulation. However, mixotrophic cultures also face the problem of light limitation, and depending on the relative concentrations of the organic carbon source and light intensity, the interaction between the heterotrophic and photoautotrophic metabolic activities can have negative effects on cell growth and oil accumulation. Systems that separate the two metabolic activities in time or space, such as cyclic photoautotrophic–heterotrophic cultures, sequential heterotrophic–photoautotrophic cultures, and sequential photoautotrophic–mixotrophic cultures, can all be used to improve oil productivity. However, the effectiveness of each system depends on the strain of microalgae and other culture conditions