Phenolics and polyphenolics in foods, beverages and spices: Antioxidant activity and health effects – A review

Xylanases are hydrolytic enzymes which randomly cleave the β 1,4 backbone of the complex plant cell wall polysaccharide xylan. Diverse forms of these enzymes exist, displaying varying folds, mechanisms of action, substrate specificities, hydrolytic activities (yields, rates and products) and physicochemical characteristics. Research has mainly focused on only two of the xylanase containing glycoside hydrolase families, namely families 10 and 11, yet enzymes with xylanase activity belonging to families 5, 7, 8 and 43 have also been identified and studied, albeit to a lesser extent. Driven by industrial demands for enzymes that can operate under process conditions, a number of extremophilic xylanases have been isolated, in particular those from thermophiles, alkaliphiles and acidiphiles, while little attention has been paid to cold-adapted xylanases. Here, the diverse physicochemical and functional characteristics, as well as the folds and mechanisms of action of all six xylanase containing families will be discussed. The adaptation strategies of the extremophilic xylanases isolated to date and the potential industrial applications of these enzymes will also be presented.

Xylanases, xylanase families and extremophilic xylanases

Despite an increased knowledge of microbial xylanolytic systems in the past few years, further studies are required to achieve a complete understanding of the mechanism of xylan degradation by microorganisms and their enzymes. The enzyme system used by microbes for the metabolism of xylan is the most important tool for investigating the use of the second most abundant polysaccharide (xylan) in nature. Recent studies on microbial xylanolytic systems have generally focussed on induction of enzyme production under different conditions, purification, characterization, molecular cloning and expression, and use of enzyme predominantly for pulp bleaching. Rationale approaches to achieve these goals require a detailed knowledge of the regulatory mechanism governing enzyme production. This review will focus on complex xylan structure and the microbial enzyme complex involved in its complete breakdown, studies on xylanase regulation and production and their potential industrial applications, with special reference to biobleaching.

Microbial xylanases and their industrial applications: a review.

Nanofluids, the fluid suspensions of nanomaterials, have shown many interesting properties, and the distinctive features offer unprecedented potential for many applications. This paper summarizes the recent progress on the study of nanofluids, such as the preparation methods, the evaluation methods for the stability of nanofluids, and the ways to enhance the stability for nanofluids, the stability mechanisms of nanofluids, and presents the broad range of current and future applications in various fields including energy and mechanical and biomedical fields. At last, the paper identifies the opportunities for future research.

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A review on nanofluids: preparation, stability mechanisms, and applications

Phenolics in Food and Nutraceuticals is the first single-source compendium of essential information concerning food phenolics. This unique book reports the classification and nomenclature of phenolics, their occurrence in food and nutraceuticals, chemistry and applications, and nutritional and health effects. In addition, it describes antioxidant activity of phenolics in food and nutraceuticals as well as methods for analysis and quantification. Each chapter concludes with an extensive bibliography for further reading. Food scientists, nutritionists, chemists, biochemists, and health professionals will find this book valuable.

Phenolics in food and nutraceuticals

Production of novel halo-alkali-thermo-stable xylanase by a newly isolated moderately halophilic and alkali-tolerant Gracilibacillus sp. TSCPVG

Decolourisation of Acid orange 7 in a microbial fuel cell with a laccase-based biocathode: Influence of mitigating pH changes in the cathode chamber.

Natural fermentation of finger millet (Eleusine coracana) was carried out for 48 h. Microbiological and chemical analysis was performed throughout the fermentation process. The fermentation was heterolactic dominated by lactic acid bacteria accompanied by the production of lactic and acetic acids with decrease in pH and increase in titratable acidity. The microbial population increased until 18 to 24 h accompanied by a rapid decrease in total and reducing sugars. The microflora stabilized between 24 and 48 h, during which time the total and α-amylase activities increased with accumulation of sugars. Total free amino acids also increased. Yeast counts were low and moulds and coliforms were absent. Repeated fermentations showed consistency in the qualitative and quantitative changes in microflora. Five predominant types of bacteria, strains belonging to Leuconostoc, Pediococcus and Lactobacillus were identified. Of these only one type, Pediococcus, dominated (>80%) in the latter half of fermentation.

Microbial population and biochemical changes in fermenting finger millet (Eleusine coracana)

Mutants of Thiosphaera pantotropha defective in chemolithoautotrophic growth were obtained by transpositional mutagenesis with Tn5 coding for kanamycin resistance. The suicide vehicle for introducing Tn5 to T. pantotropha was pSUP5011 harbored by Escherichia coli. Kanamycin-resistant isolates were screened for the inability to grow with reduced sulfur compounds (Sox-). Four classes of Sox- mutants were obtained. Three were of different pleiotropic phenotypes: (i) unable to grow with formate, nitrate, and xanthine; (this class strongly suggested the involvement of a molybdenum cofactor in inorganic sulfur-oxidizing ability); (ii) no growth with hydrogen; (iii) slight growth with hydrogen and formate. Two plasmids, pHG41 (about 450 kilobase pairs) and pHG42 (110 kilobases), were identified in lysates of T. pantotropha. In one Sox- mutant pHG41 could not be detected. Revertant analysis suggested that pHG41 and pHG42 were not involved in the Sox character.

Tn5-induced mutations affecting sulfur-oxidizing ability (Sox) of Thiosphaera pantotropha.

More than 80 per cent of wastewater from industries is discharged into receiving water bodies without any pollution control. Microbial fuel cells (MFCs) are a promising technology for the simultaneous treatment of wastewater and electricity production. With regard to azo-dye containing wastewater (e.g. from textile manufacturing), the dye may be fed via the anode chamber containing electrochemically active bacteria or via the cathode chamber containing laccase enzyme as catalyst for oxygen reduction. This study investigated which of the two approaches is the best with regard to rate of decolourization of the dye (Acid orange 7), COD reduction and electricity production. The power density was higher for the MFCDye cathode (50±4 mW m-2, COD reduction 80.4±1.2%) compared with 42.5±2.6 mW m-2 (COD reduction 69±2%) for MFCDye anode. The time required for decolourization was longer in the MFCDye anode (Shewanella oneidensis) where only 20% decolourization was obtained after 24 h compared to 80% for the MFCDye cathode. The anodic dye degradation products were unstable when exposed to air resulting in regaining of colour. In case of degradation by laccase in the cathode chamber, the decolourization products were stable and simpler in chemical structure as determined by GC-MS. This work suggests that feeding azo dyes in cathode chambers of MFCs containing laccase is a better way of treating the dyes compared to the commonly used approach of feeding the dye in the anode chamber provided enzyme activity can be sustained.

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Degradation of azo dye (Acid orange 7) in a microbial fuel cell: comparison between anodic microbial-mediated reduction and cathodic laccase-mediated oxidation

T.S. Chandra

Papers

Production of novel halo-alkali-thermo-stable xylanase by a newly isolated moderately halophilic and alkali-tolerant Gracilibacillus sp. TSCPVG

Decolourisation of Acid orange 7 in a microbial fuel cell with a laccase-based biocathode: Influence of mitigating pH changes in the cathode chamber.

Microbial population and biochemical changes in fermenting finger millet (Eleusine coracana)

Tn5-induced mutations affecting sulfur-oxidizing ability (Sox) of Thiosphaera pantotropha.

Degradation of azo dye (Acid orange 7) in a microbial fuel cell: comparison between anodic microbial-mediated reduction and cathodic laccase-mediated oxidation