Debajit Borah

Isolation and characterization of the new indigenous Staphylococcus sp. DBOCP06 as a probiotic bacterium from traditionally fermented fish and meat products of Assam state

Abstract Traditionally fermented fish and meat products are known for their probiotic values. An approach was made for the very first time to isolate and characterize novel indigenous probiotic bacterial strains from traditionally fermented fish and meat products of Assam, India, which is known as the biodiversity hotspot of the country with largely unexplored economically important microorganisms. The most potent probiotic isolate was identified as Staphylococcus sp. DBOCP6 (GenBank accession no. KR706310) on the basis of 16S rDNA sequencing technique. The new isolate was found to be non-hemolytic and nonpathogenic on the basis of its susceptibility against broad and narrow spectrum antibiotics. It shows antagonistic effect against E. coli MTCC 40. Its viability in presence of lysozyme, bile salt (4%), and a pH range of 1–10 signifies its ability to survive throughout the gastrointestinal tract. It also shows significant value of hydrophobicity (33.1%) along with a higher value of auto-aggregation (71.43%) indicates its ability to adhere to the intestinal wall on the basis of its cell surface traits. The high thermal death point of the isolate (100 °C) indicates its suitability for further commercial exploitation. Based on the above observations, it could be concluded that the novel Staphylococcus sp. strain DBOCP6 can serve as a potential probiotic candidate for industrial exploitation.

Biogenic synthesis of palladium nanoparticles and their applications as catalyst and antimicrobial agent

This paper describes a simple in-situ process of synthesizing highly dispersed palladium nanoparticles (PdNPs) using aqueous leaf extract of GarciniapedunculataRoxb as bio-reductant and starch (0.3%) as bio-stabilizer. The PdNPs are characterized by techniques like FTIR, TEM, SEM-EDX, XRD and XPS analysis. It is worthnoting thatwhen the synthesis of nanoparticles was carried out in absence of starch, agglomeration of particles has been noticed.The starch-assisted PdNPs showed excellent aqueous-phase catalytic activities for three important reactions: the Suzuki-Miyaura cross-coupling reactions of aryl halides (aryl bromides and iodides) with arylboronic acids; selective oxidations of alcohols to corresponding carbonyl compounds; and reduction of toxic Cr(VI) to nontoxic Cr(III). Our catalyst could be reused up to four cycles without much compromising with its activity. Furthermore, the material also demonstrated excellent antimicrobial and anti-biofilm activities against a novel multidrug resistant clinical bacterial isolate Cronobactersakazakii strain AMD04. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of PdNPswere found to be 0.06 and 0.12 mM respectively.

Plasmid Curing of a Novel Hydrocarbon Degrading Bacillus cereus Strain DRDU1 Revealed its Involvement in Petroleum Oil Degradation

Plasmid curing of a novel hydrocarbon degrading Bacillus cereus strain DRDU1 was carried out to confirm the possible involvement of plasmid genes in hydrocarbon degradation. Plasmid curing was done by using 100 μg/mL of ethidium bromide, which is approximately 12 kb in size. Hydrocarbon degradation potential of the plasmid cured strain was compared with that of the control and the percentage hydrocarbon degradation of diesel, kerosene, crude oil and used engine oil after 28 days of incubation was confirmed by gas liquid chromatographic (GLC) analysis. The percentage hydrocarbon degradation for diesel, kerosene, crude oil and used engine oil (2% v/v) in Bushnell and Haas (BH) broth was found to be decreasing up to 30%, 21%, 13%, and 6% respectively for the plasmid cured strain, from its initial values of 99%, 96%, 84%, and 29% by the uncured strain. This study clearly confirms that the respective petroleum hydrocarbon degradation in this case is both plasmid and chromosomal encoded as considerable amount of degradation can be seen by the plasmid cured strain also. Due to this the strain is beneficial for in-situ bioremediation purpose, as the loss of plasmid due to any environmental or biological factor will not stop its potential to degrade hydrocarbon oil.

Molecular characterization of biosurfactant producing Bacillus cereus strain DRDU1 for its potential application in bioremediation and further EOR studies

Abstract Environmental pollution by crude oil during petroleum exploration is a global issue of concern. It largely alters the physicochemical property of soil and water which makes them toxic for crops and aquatic organisms to survive. Bacillus cereus strain DRDU1 (Genbank accession no. KF273330.1) is an endospore forming potential hydrocarbon degrader which was isolated from an automobile engine. The isolate could achieve up to 96 and 84% kerosene and crude oil degradation with respective cfu of (6.3 ± 2.31) × 109 and (13.67 ± 2.52) × 108 cells/mL. On the other hand it also showed its potential to degrade 74 and 67% of kerosene and crude oil in nitrate (N) and phosphate (P) deficient media with corresponding cfu (10 ± 1.73) × 108 and (6 ± 2.65) × 106 cells/mL. This indicates its potential to survive under nutrient stress condition. The strain was reported to be capable of producing biosurfactant which may play role in petroleum biodegradation and may be a potential tool for Microbial Enhanced Oil Recovery (MEOR) studies in future. Herein the presence of sfp gene in the isolate was confirmed which may be responsible for its ability to synthesize biosurfactant for hydrocarbon degradation and also for its stress tolerant potential. It was further characterized and the hypothetical protein sequence encoded by this gene is also proposed.

Characterization of a Newly Isolated Probiotic Strain from Oecophylla smaragdina, an Edible Insect Popular Among the Indigenous Communities of Northeast India

Northeast India is amongst the 34 Biodiversity Hot Spots of the world with large number of unexplored flora and fauna. A total of 74 potential isolates with probiotic properties were isolated from Oecophylla smaragdina, an edible insect used by local tribes as a nutritious medicinal food source out of which, the most potential probiotic candidate was identified as Bacillus sp. PD6 by 16S rRNA sequencing. Cell surface trait analysis shows hydrophobicity and auto-aggregation percentage of 46.2 ± 0.32% and 61.41 ± 0.28% respectively. The cell free extract (CFE) of the isolate shows the presence of essential amino acids viz, lysine, valine, leucine, isoleucine, and threonine indicating its nutritional value. It survives significantly at pH range from 1 to 10 and capable of hydrolyzing bile salt. The CFE shows antagonistic effect against B. cereus ATCC 11778, E. coli ATCC 25922 and L. monocytogenes ATCC BAA751. FTIR spectra of bacterial exo-polysaccharide shows the presence of νC=C–H stretch, νN–H stretch, νC–H stretch, νC–H bending and νC=O stretch bonds. It was found to be non-cytotoxic against primary mouse liver cell line and sheep erythrocytes and also, sensitive against wide range of broad and narrow spectrum antibiotics making it recommendable for human consumption.