Applied Biochemistry

The ability to utilize sterols as a sole source of carbon was studied in 80 strains and consortia of hydrocarbon-oxidizing bacteria. One of the strains, which efficiently transformed both individual sterols and their mixtures, was identified as Mycobacterium neoaurum, based on the analysis of the sequence of the 16S rRNA gene.

Beads with enhanced-stability acid media, which were based on alginate and chitosan functionalized by succinylation (increasing the anionic charges able to retain protons) or by acylation (improving matrix hydrophobicity), were developed for immobilization of bacterial cells. Beads (3 mm diameter) formed by ionotropic gelation with CaCl(2) presented good mechanical characteristics. After 30 min incubation of viable free Lactobacillus rhamnosus cells in simulated gastric fluid (pH 1.5), we noticed that the level of viable bacteria was undetectable. Bacterial immobilization in native-alginate-based beads generated a viable-cell count of 22-26%, whereas, when entrapped in succinylated alginate and chitosan beads, the percentage of viable cells was of 60 and 66%, respectively. Best viability (87%) was found for bacteria immobilized in N -palmitoylaminoethyl alginate, which affords a high protective effect, probably due to long alkyl pendants that improve the beads' hydrophobicity, l...

Peroxidase (EC 1.11.1.7; donor: hydrogen peroxide oxidoreductase) is an oxidoreductase enzyme found in many fruits and vegetables. This enzyme was purified from sweet gourd (Cucurbita moschata Lam. Poiret) by ammonium sulphate precipitation and CM-Sephadex ion-exchange chromatography. Furthermore, optimum pH, optimum temperature, optimum ionic strength, stable pH, and stable temperature conditions were determined as 7.2, 50°C, 0.4 M, 8.0, and 40°C, respectively. The molecular weight (MW) of the enzyme was estimated to be 85 kDa by SDS-PAGE method. The values of Km and Vmax were calculated from the Lineweaver-Burk graph for guaiacol/H2O2 substrate patterns.

Phytochemicals such as polyphenols and carotenoids are gaining importance because of their contribution to human health and their multiple biological effects such as antioxidant, antimutagenic, anticarcinogenic, and cytoprotective activities and their therapeutic properties. Banana peel is a major by-product in pulp industry and it contains various bioactive compounds like polyphenols, carotenoids, and others. In the present study, effect of ripening, solvent polarity on the content of bioactive compounds of crude banana peel and the protective effect of peel extracts of unripe, ripe, and leaky ripe banana fruit on hydrogen peroxide-induced hemolysis and their antioxidant capacity were investigated. Banana (Musa paradisica) peel at different stages of ripening (unripe, ripe, leaky ripe) were treated with 70% acetone, which were partitioned in order of polarity with water, ethyl acetate, chloroform (CHCl3), and hexane sequentially. The antioxidant activity of the samples was evaluated by the red cell hemolysis assay, free radical scavenging (1,1-diphenyl-2-picrylhydrazyl free radical elimination) and superoxide dismutase activities. The Folin–Ciocalteu's reagent assay was used to estimate the phenolic content of extracts. The findings of this investigation suggest that the unripe banana peel sample had higher antioxidant potency than ripe and leaky ripe. Further on fractionation, ethyl acetate and water soluble fractions of unripe peel displayed high antioxidant activity than CHCl3 and hexane fraction, respectively. A positive correlation between free radical scavenging capacity and the content of phenolic compound were found in unripe, ripe, and leaky ripe stages of banana peel.

The ability of pro- and eukaryotic microorganisms to synthesize growth-stimulating phytohormones is reviewed, with emphasis on pathways of biosynthesis of these compounds and their effects on physiological and biochemical properties of the producers. Phytohormones are viewed as specific mediators in interactions between various organisms inhabiting the same ecological niche, the biological role of which is not limited to processes taking place in plants. In addition to setting forth theoretical aspects of this problem, the review underscores the need to utilize such producer microorganisms in plant cultivation and biotechnology.

It is imperative to slash the cost of algal oil to less than $50 bbl−1 for successful algal biofuel production. Use of municipal wastewater for algal cultivation could obviate the need for freshwater and the nutrients—N and P. It would also add CO2 through bacterial activity. Chlorella minutissima Fott et Nova dominated the entire phycoflora year around and through each stage of the wastewater treatment at the oxidation pond system of Wazirabad (Delhi) in India. The ability to grow so profusely in such varied and contrasting situations made this alga unique. Besides pollution tolerance, it grew heterotrophically in dark under acidic conditions and as a mixotroph in presence of light over a range of organic C substrates. It could utilize both ammoniacal and nitrate nitrogen, survived anaerobicity, 5% NaCl and −10 bar of osmotic stress. C. minutissima grew at pH 4–11 and raised the pH set initially by 1 to 3 units in 7.5 h. It showed gigantism and largely kept afloat in presence of utilizable organic carbon, while flocculated in mineral medium and on aging. The alga also possessed potential for biofuel production. The studied parameters indicate why C. minutissima was a potential biomass builder in municipal sewage and could be used to determine which other alga(e) may serve the purpose.

Methods for the quantification of total and accessible reducing ends on traditional cellulose substrates have been evaluated because of their relevance to enzyme-catalyzed cellulose saccharification. For example, quantification of accessible reducing ends is likely to be the most direct measure of substrate concentration for the exo-acting, reducing end-preferring cellobiohydrolases. Two colorimetric assays (dinitrosalicylic acid [DNS] and bicinchoninic acid [BCA] assay) and a radioisotope approach (NaB3H4 labeling) were evaluated for this application. Cellulose substrates included microcrystalline celluloses, bacterial celluloses, and filter paper. Estimates of the number of reducing ends per unit mass cellulose were found to be dependent on the assay system (i.e. the DNS and BCA assays gave strikingly different results). DNS-based values were several-fold higher than those obtained using the BCA assay, with fold-differences being substrate specific. Sodium borohydride reduction of celluloses, using cold or radiolabeled reagent under relatively mild conditions, was used to assess the number of surface (solvent-accessible) reducing ends. The results indicate that 30–40% of the reducing ends on traditional cellulose substrates are not solvent accessible; that is, they are buried in the interior of cellulose structures and thus not available to exo-acting enzymes.