Enterobacter sp. NRG4 was shown to excrete chitinase into the culture supernatant when cultivated in medium containing chitin. A 60 kDa extracellular chitinase was purified to homogeneity and characterized. The enzyme hydrolyzed swollen chitin, colloidal chitin, regenerated chitin and glycol chitin but did not hydrolyze chitosan. Chitin is composed of repeating N-acetyl D-glucosamine residues and is a component of crustacean exoskeleton, diatoms, fungal cell walls, and squid pens. Chitin is a versatile and promising biopolymer with numerous industrial, medical and commercial uses. However, it is difficult to purify and modify chemically. Hence identification of chitin modifying enzymes and elucidation of their activities could facilitate the efficient production of specific chitin products. The biodegradation of chitin requires the synergistic action of several hydrolytic enzymes

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.

The gut microflora is an important constituent in the intestinal mucosal barrier and has been introduced as the concept of probiotic therapy that beneficially affects the host by improving its intestinal microbial balance. Therefore, the main objective of the study was to explore the protective potential of various lactobacilli strains for murine giardiasis. By experimentation, it was found that the probiotic supplementation of either Lactobacillus casei, L. acidophilus, L. plantarum, or L. rhamnosus GG, 7 days prior to inoculation with G. lamblia trophozoites, reduced the rate of cyst excretion compared with Giardia-infected mice. Interestingly, L. GG was found to be the most effective probiotic in reducing the duration of giardia cycle and acts as an effective prophylactic probiotic for murine giardiasis but needs to be clinically correlated due to entirely different human microflora.

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.

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 (1 8%) 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.