R. P. Tiwari

Bio: R. P. Tiwari is an academic researcher from Panjab University, Chandigarh. The author has contributed to research in topics: Aflatoxin & Solid-state fermentation. The author has an hindex of 12, co-authored 29 publications receiving 849 citations.

Microbial alkaline pectinases and their industrial applications: a review.

Abstract: The biotechnological potential of pectinolytic enzymes from microorganisms has drawn a great deal of attention from various researchers worldwide as likely biological catalysts in a variety of industrial processes. Alkaline pectinases are among the most important industrial enzymes and are of great significance in the current biotechnological arena with wide-ranging applications in textile processing, degumming of plant bast fibers, treatment of pectic wastewaters, paper making, and coffee and tea fermentations. The present review features the potential applications and uses of microbial alkaline pectinases, the nature of pectin, and the vast range of pectinolytic enzymes that function to mineralize pectic substances present in the environment. It also emphasizes the environmentally friendly applications of microbial alkaline pectinases thereby revealing their underestimated potential. The review intends to explore the potential of these enzymes and to encourage new alkaline pectinase-based industrial technology.

Production of an Antifungal Chitinase from Enterobacter sp. NRG4 and its Application in Protoplast Production

Abstract: In this study flake chitin, crab shell chitin, mushroom stalk, fungal cell wall, wheat bran and rice bran were used as substrate for chitinase production by Enterobacter sp. NRG4 under submerged and solid state fermentation (SSF) conditions. Enterobacter sp. NRG4 produced 72 and 49.7 U/ml of chitinase in presence of cell walls of Candida albicans and Fusarium moniliforme in submerged fermentation. Under SSF, maximum chitinase production was 965 U/g solid substrate with flake chitin and wheat bran (1:3 ratio) at 75% moisture level after 144 h. The purified chitinase inhibited hyphal extension of Fusarium moniliforme, Aspergillus niger, Mucor rouxi and Rhizopus nigricans. The chitinase was effective in release of protoplasts from Trichoderma ressei, Pleurotus florida, Agaricus bisporus and Aspergillus niger. Protoplasts yield was maximum with 60 mg of 24 h old fungal mycelium incubated with 60 U of chitinase and 60 U of cellulase.

Chitinase production in solid-state fermentation by Enterobacter sp. NRG4 using statistical experimental design.

Abstract: The optimization of nutrient levels for chitinase production by Enterobacter sp. NRG4 in solid-state fermentation conditions (SSF) was carried out using response surface methodology (RSM) based on central composite design (CCD). The design was employed by selecting wheat bran-to-flake chitin ratio, moisture level, inoculum size, and incubation time as model factors. The results of first-order factorial design experiments showed that all four independent variables have significant effects on chitinase production. The optimum concentrations for chitinase production were wheat bran-to-flake chitin ratio, 1; moisture level, 80%; inoculum size, 2.6 mL; and incubation time, 168 h. Using this statistical optimization method, chitinase production was found to increase from 616 U · g−1 dry weight of solid substrate to 1475 U · g−1 dry weight of solid substrate.

Resistance to metal ions and antibiotics in Escherichia coli isolated from foodstuffs.

Abstract: Summary Of 39 strains of Escherichia coli isolated from foodstuffs, all were resistant to at least one of a panel of four metallic ions tested. The most common resistance (94.9%) was against cadmium, followed by arsenate (76.9%), silver (71.8%) and mercury (61.5%). Multiple resistance to three (35.9%) or four (38.5%) metals was seen more often than resistance to two (18%) or one (7.7%) metal only. The opposite trend was seen in antibiotic resistance; resistance to one (30%) or two (49%) antibiotics was more common than to three or more antibiotics (13%). Resistance to kanamycin correlated with resistance to silver and cadmium ions and resistance to ampicillin or cephalothin was, with one exception, associated with resistance to cadmium ions.

Yersinia enterocolitica: the charisma continues.

Abstract: Yersinia enterocolitica, a gram-negative coccobacillus, comprises a heterogeneous group of bacterial strains recovered from animal and environmental reservoirs. The majority of human pathogenic strains are found among distinct serogroups (e.g. O:3, O:5,27, O:8, O:9) and contain both chromosome- and plasmid (60 to 75 kb)-mediated virulence factors that are absent in "avirulent" strains. While Y. enterocolitica is primarily a gastrointestinal tract pathogen, it may produce extraintestinal infections in hosts with underlying predisposing factors. Postinfection sequelae include arthritis and erythema nodosum, which are seen mainly in Europe among patients with serogroups O:3 and O:9 infection and HLA-B27 antigen. Y. enterocolitica is acquired through the oral route and is epidemiologically linked to porcine sources. Bacteremia is prominent in the setting of immunosuppression or in patients with iron overload or those being treated with desferrioxamine. metastatic foci following bacteremia are common and often involve the liver and spleen. Of particular concern is blood transfusion-related bacteremia. Evidence has accumulated substantiating the role of Y. enterocolitica as a food-borne pathogen that has caused six major outbreaks in the United States. The diagnosis of Y. enterocolitica gastroenteritis is best achieved through isolation of the bacterium on routine or selective bacteriologic media. When necessary, serogrouping, biogrouping, and assessment for plasmid-encoded virulence traits may aid in distinguishing virulent from "avirulent" strains. Epidemiologically, outside of identified food-borne outbreaks, the source (reservoir) of Y. enterocolitica in sporadic cases is speculative. Therefore, prevention and control measures are difficult to institute.