Sudhir B. Chincholkar

Probiotic Bile Salt Hydrolase: Current Developments and Perspectives

Probiotic has modernized the current dietetic sense with novel therapeutic and nutritional benefits to the consumers. The presence of bile salt hydrolase (BSH) in probiotics renders them more tolerant to bile salts, which also helps to reduce the blood cholesterol level of the host. This review focuses on the occurrence of bile salt hydrolase among probiotics and its characterization, importance, applications, and genetics involved with recent updates. Research on bile salt hydrolase is still in its infancy. The current perspective reveals a huge market potential of probiotics with bile salt hydrolase. Intensive research in this field is desired to resolve some of the lacunae.

Production, purification and chemical characterization of the catecholate siderophore from potent probiotic strains of Bacillus spp.

The aim of the present study was to characterize the probiotic qualities of Bacillus isolates and study their siderophore prior to possible siderophoregenic probiotic application for iron nutrition in animals and humans. Bacillus strains were selectively isolated from dairy waste and mango pulp waste. Best two siderophore positive isolates, JHT3 and DET6 showed high homology with Bacillus megaterium (98%) and B. subtilis (99%), respectively, using partial 16S-rRNA sequencing and biochemical characterization. These isolates produced catecholate type of siderophore under iron stressed conditions and were screened for probiotic properties as per WHO and FAO guidelines. Spores of these strains showed excellent tolerance in partially simulated gastrointestinal tract conditions and exhibited antimicrobial activity against organisms such as Staphylococcus aureus, Micrococcus flavus and Escherichia coli. Importantly, these isolates were susceptible to the most of the antibiotics tested, in conflict that they would not donate resistance determinants if administered in the form of probiotic preparations.

Siderophore production by a marine Pseudomonas aeruginosa and its antagonistic action against phytopathogenic fungi

A marine isolate of fluorescent Pseudomonas sp. having the ability to produce the pyoverdine type of siderophores under low iron stress (up to 10 µM iron in the succinate medium) was identified as Pseudomonas aeruginosa by using BIOLOG Breathprint and siderotyping. Pyoverdine production was optimum at 0.2% (w/v) succinate, pH 6.0, in an iron-deficient medium. Studies carried out in vitro revealed that purified siderophores and Pseudomonas culture have good antifungal activity against the plant deleterious fungi, namely, Aspergillus niger, Aspergillus flavus, Aspergillus oryzae, Fusarium oxysporum, and Sclerotium rolfsii. Siderophore-based maximum inhibition was observed against A. niger. These in vitro antagonistic actions of marine Pseudomonas against phytopathogens suggest the potential of the organism to serve as a biocontrol agent.

Siderophore Producing PGPR for Crop Nutrition and Phytopathogen Suppression

Deficiency of iron in crop results in iron chlorosis, makes them micronutrient deficient and hence sensitive to microbial infections. More than 60 phytopathogens are known to cause different plant diseases. These microbial diseases of crop plants are the major cause of severe global economic losses to agricultural crops. During the last 50 years, the control of most of the plant diseases has fully relied on the use of agrochemicals. Although this has resulted in increased production of agricultural commodities, it has several inherent problems like health hazards, biomagnification and development of pesticide resistance in the pests, and contamination of underground water. The increasing public awareness about these problems has stimulated interest in the use of biological control methods for controlling plant diseases. Past decade has witnessed increasing interest in the role of rhizobacteria for controlling plant diseases. In the present agricultural scenario, siderophore producing rhizobacteria has been recognized as potential biocontrol agents (BCAs) for controlling plant diseases.

Exploring Antagonistic Metabolites of Established Biocontrol Agent of Marine Origin

Biocontrol ability of Pseudomonas aeruginosa ID 4365, a biocontrol agent of groundnut phytopathogens from marine origin, was previously attributed to the production of pyoverdin type of siderophores. However, pyoverdin-rich supernatants of this organism showed better antifungal activity compared to equivalent amount of purified pyoverdin indicating presence of undetected metabolite(s) in pyoverdin rich supernatants. On the basis of observation that antagonistic activity was iron-dependent and iron-independent, an attempt was made to detect the presence of additional metabolites. In addition to pyoverdin, strain produced additional siderophores, viz. pyochelin and salicylic acid. Two broad spectrum antifungal compounds, viz. pyocyanin and phenazine-1-carboxylic acid, were detected, characterized, and activity against phytopathogens was demonstrated. Iron- and phosphate-dependent co-production of siderophores and phenazines was confirmed. Strain showed additional features like production of hydrogen cyanide, indol-3-acetic acid, and phosphate solubilization.

Bacillus spp. of Human Origin: A Potential Siderophoregenic Probiotic Bacteria

Bacillus spp. ST13, isolated from human stool, was evaluated for siderophoregenic and probiotic qualities prior to its possible application for iron nutrition in humans and animals. It was tested for siderophore production in iron-limiting conditions and found to produce catecholate type of siderophore on the basis of high-performance liquid chromatography (HPLC), FT-IR, NMR, and mass spectra analysis. The isolate was screened for probiotic properties as per WHO and FAO guidelines. The strain ST13 can survive stomach acidity, bile salt and partially simulated gastrointestinal tract conditions. It was susceptible to most of the antibiotic tested and showed antimicrobial activity against enteric pathogens like Salmonella typhimurium, Streptococcus pyogenes, and Staphylococcus aureus. Strain ST13 showed close similarity with Bacillus subtilis using 16S r-RNA gene sequence analysis and biochemical characterization. The methanolic extract of ST13 siderophore was evaluated for DPPH radical scavenging activity, which showed 94.55 ± 0.9% of radical scavenging effect.

A potential probiotic culture ST2 produces siderophore 2,3-dihydroxybenzoylserine under intestinal conditions.

The aim of this study was to characterise siderophores of a culture bearing better probiotic qualities of human origin. In this direction, bacterial strain ST2 was isolated from faecal sample of 6-month-old healthy infant, which showed close similarity with Escherichia coli based on 16S r-RNA gene sequence analysis and biochemical characteristics. It was tested for siderophore production under in vitro iron limiting intestinal conditions. The siderophore produced was catecholate type of 2,3-dihydroxybenzoylserine on the basis of FTIR, NMR and mass spectra analysis. The strain obeyed probiotic properties as per WHO and FAO guidelines. It showed excellent tolerance in partially simulated gastro-intestinal tract conditions, non-haemolytic nature, susceptibility to many antibiotics tested and antimicrobial activity against enteric pathogens like Salmonella typhimurium, Streptococcus pyogenes, and Staphylococcus aureus. Hence, this culture could be a possible probiotic candidate in iron nutrition, but only after conducting proper animal and human trials.

Hypochlorite digestion method for efficient recovery of PHB from Alcaligenes faecalis

We reported the optimum amount of PHB accumulated by Alcaligenes faecalis during its 24 h growth under nitrogen deficient conditions. After 24 h incubation decrease in the amount of PHB was recorded. Hypochlorite digestion of biomass of organism followed by extraction with a solvent system consisting of 1:1 mixture of ethanol and acetone resulted in efficient recovery of PHB vis-à-vis earlier methods. This solvent system gave a high recovery yield, i.e. 5.6 gL−1 vis-à-vis earlier reported yield, 1.34 gL−1 (by same method), 0.63 gL−1 (by chloroform extraction method) and 1.1 gL−1 (by dispersion method).

Microbial Iron Chelators: A Sustainable Tool for the Biocontrol of Plant Diseases

Since prehistoric times, control of plant diseases has remained a challange to mankind. In spite of large scale use of agro-chemicals and pesticides since long, number of plant diseases are still beyond the control. Every year agricultural losses due to pests and diseases amount to Rs. 20,000 crores and exports worth more than Rs. 1,000 crore are restricted owing to poor quality.

Production of hyaluronic acid from Streptococcus zooepidemicus MTCC 3523 and its wound healing activity.

Exopolysaccharide produced and purified from Streptococcus zooepidemicus MTCC 3523 was identified as hyaluronic acid (HA) based on IR and NMR spectroscopy while its Mw was found to be 5.38 × 10(5)Da. HA produced passed bacterial endotoxin test and showed significant wound healing activity in Wistar rats on 12th and 16th day.