Biodegradation of chlorpyrifos using isolates from contaminated agricultural soil, its kinetic studies.

Extensive pesticides use is negatively disturbing the environment and humans. Pesticide bioremediation with eco-friendly techniques bears prime importance. This study evaluates the bioremediation of chlorpyrifos in soil using indigenous Bacillus cereus Ct3, isolated from cotton growing soils. Strains were identified through ribotyping (16s rRNA) by Macrogen (Macrogen Inc. Geumchen-gu, South Korea). Bacillus cereus Ct3 was resistant up to 125 mg L-1 of chlorpyrifos and successfully degraded 88% of chlorpyfifos in 8 days at pH 8. Bacillus cereus Ct3 tolerated about 30-40 °C of temperature, this is a good sign for in situ bioremediation. Green compost, farmyard manure and rice husk were tested, where ANOVA (P < 0.05) and Plackett-Burman design, results indicated that the farm yard manure has significant impact on degradation. It reduced the lag phase and brought maximum degradation up to 88%. Inoculum size is a statistically significant (P < 0.05) factor and below 106 (CFU g-1) show lag phase of 4-6 days. Michaelis-Menten model results were as follows; R2 = 0.9919, Vmax = 18.8, Ks = 121.4 and Vmax/Ks = 0.1546. GC-MS study revealed that chlorpyrifos first converted into diethylthiophosphoric acid and 3,5,6-trichloro-2-pyridinol (TCP). Later, TCP ring was broken and it was completely mineralized without any toxic byproduct. Plackett-Burman design was employed to investigate the effect of five factors. The correlation coefficient (R2) between experimental and predicted value is 0.94. Central composite design (CBD) was employed with design matrix of thirty one predicted and experimental values of chlorpyrifos degradation, having "lack of fit P value" of "0.00". The regression coefficient obtained was R2 = 0.93 which indicate that the experimental vales and the predicted values are closely fitted. The most significant factors highlighted in CBD/ANOVA and surface response plots were chlorpyrifor concentration and inoculum size. Bacillus cereus Ct3 effectively degraded chlorpyrifos and can successfully be used for bioremediation of chlorpyrifos contaminated soils.

Identification of oral cavity biofilm forming bacteria and determination of their growth inhibition by Acacia arabica, Tamarix aphylla L. and Melia azedarach L. medicinal plants.

OBJECTIVE: Biofilms are complex, multi-species bacterial communities that colonize the oral cavity in the form of plaque and are known to cause dental caries and periodontal disease. Present study demonstrated the potential of three selected medicinal plants against isolated and identified dental biofilm forming strains. METHODS: Pathogenic bacteria from dental biofilms were isolated, cultured, identified by phylogenetic analysis using PCR-based 16S ribosomal RNA (or 16S rRNA) nucleotide sequences and were analyzed for their biofilm forming capability. The antimicrobial activity of the three important medicinal plant extracts (Acacia arabica, Tamarix aphylla L. and Melia azadirachta L.) was determined against the highest biofilm forming bacteria. RESULTS: Phylogenetic analysis revealed that the 19 strains belonged to Proteobacteria, Firmicutes and Actinobacteria. Among the 19 isolates, eleven strains were found to possess high biofilm formation capability comparatively and antimicrobial activity assay showed that the selected plants considerably inhibited their growth. Extract from A. arabica stem had strong effect on the ability of bacteria isolated from dental carries as evident by up to 73% reduction in biofilm formation on surface pre-treated with extract from this plant. The same extract also showed tremendous biofilm cleaning potential up to 87% of the biofilm. CONCLUSION: The results suggested that the extracts of selected medicinal plants could be used for protection against pathogenic dental biofilm causing bacteria and attempts should be taken by pharmaceutical industries to utilize it in dental caring products.

Random mutagenesis and media optimisation for hyperproduction of cellulase from Bacillus species using proximally analysed Saccharum spontaneum in submerged fermentation.

This study deals with the isolation of novel mutant of Bacillus and optimisation of media for the hyperproduction of cellulase. Cellulase-producing Bacillus PC-BC6 was subjected to physical and chemical mutagenesis to enhance the cellulolytic potential. Later, mutagenesis isolates were screened both qualitatively and quantitatively. Among all the tested isolates, Bacillus N3 yielded maximum (CMCase 1250 IU/mL/min and FPase 629 IU/mL/min) activity. The Bacillus N3 strain exhibited 1.7-fold more enzyme production as compared with the parental strain. Proximate analysis of untreated and pretreated Saccharum spontaneum was carried out to improve cellulase production. Three different media were tested for the production of cellulase, among which M2 medium containing MgSO4, pretreated S. spontaneum, K2HPO4, (NH4)2SO4 and peptone was found to be the best for maximum enzyme production by mutant Bacillus N3.