Fundamental features of microbial cellulose utilization are examined at successively higher levels of aggregation encompassing the structure and composition of cellulosic biomass, taxonomic diversity, cellulase enzyme systems, molecular biology of cellulase enzymes, physiology of cellulolytic microorganisms, ecological aspects of cellulase-degrading communities, and rate-limiting factors in nature. The methodological basis for studying microbial cellulose utilization is considered relative to quantification of cells and enzymes in the presence of solid substrates as well as apparatus and analysis for cellulose-grown continuous cultures. Quantitative description of cellulose hydrolysis is addressed with respect to adsorption of cellulase enzymes, rates of enzymatic hydrolysis, bioenergetics of microbial cellulose utilization, kinetics of microbial cellulose utilization, and contrasting features compared to soluble substrate kinetics. A biological perspective on processing cellulosic biomass is presented, including features of pretreated substrates and alternative process configurations. Organism development is considered for "consolidated bioprocessing" (CBP), in which the production of cellulolytic enzymes, hydrolysis of biomass, and fermentation of resulting sugars to desired products occur in one step. Two organism development strategies for CBP are examined: (i) improve product yield and tolerance in microorganisms able to utilize cellulose, or (ii) express a heterologous system for cellulose hydrolysis and utilization in microorganisms that exhibit high product yield and tolerance. A concluding discussion identifies unresolved issues pertaining to microbial cellulose utilization, suggests approaches by which such issues might be resolved, and contrasts a microbially oriented cellulose hydrolysis paradigm to the more conventional enzymatically oriented paradigm in both fundamental and applied contexts.

/pdf/microbial-cellulose-utilization-fundamentals-and-4yec12qx1c.pdf

Microbial cellulose utilization: fundamentals and biotechnology.

Bioethanol production from agricultural wastes: An overview

Biopolymer-based hydrogels as scaffolds for tissue engineering applications: a review

Antioxidant and prooxidant properties of flavonoids.

This article reviews developments in the technology for ethanol production from lignocellulosic materials by “enzymatic” processes. Several methods of pretreatment of lignocelluloses are discussed, where the crystalline structure of lignocelluloses is opened up, making them more accessible to the cellulase enzymes. The characteristics of these enzymes and important factors in enzymatic hydrolysis of the cellulose and hemicellulose to cellobiose, glucose, and other sugars are discussed. Different strategies are then described for enzymatic hydrolysis and fermentation, including separate enzymatic hydrolysis and fermentation (SHF), simultaneous saccharification and fermentation (SSF), non-isothermal simultaneous saccharification and fermentation (NSSF), simultaneous saccharification and co-fermentation (SSCF), and consolidated bioprocessing (CBP). Furthermore, the by-products in ethanol from lignocellulosic materials, wastewater treatment, commercial status, and energy production and integration are reviewed.

/pdf/acid-based-hydrolysis-processes-for-ethanol-from-5bj47066uh.pdf

Acid-based hydrolysis processes for ethanol from lignocellulosic materials: a review.

BACKGROUND: This study was designed to evaluate and compare antioxidant capacity and radical scavenging activity of naringin and its aglycone by different in vitro assays. The effects of flavanones on lipid peroxidation, glutathione (GSH) oxidation and DNA cleavage were also assessed.

RESULTS: The results showed that naringenin exhibited higher antioxidant capacity and hydroxyl and superoxide radical scavenger efficiency than naringin. Our results evidenced that glycosylation attenuated the efficiency in inhibiting the enzyme xanthine oxidase and the aglycone could act like a more active chelator of metallic ions than the glycoside. Additionally, naringenin showed a greater effectiveness in the protection against oxidative damage to lipids in a dose-dependent manner. Both flavanones were equally effective in reducing DNA damage. However, they show no protective effect on oxidation of GSH.

CONCLUSION: The data obtained support the importance of characterizing the ratio naringin/naringenin in foods when they are evaluated for their health benefits. Copyright © 2010 Society of Chemical Industry

Antioxidant properties, radical scavenging activity and biomolecule protection capacity of flavonoid naringenin and its glycoside naringin: a comparative study

Kinetic properties and thermal behaviour of polygalacturonase used in fruit juice clarification

Immobilization of naringinase from Aspergillus niger CECT 2088 in poly(vinyl alcohol) cryogels for the debittering of juices

Kinetics of cellulose saccharification by Trichoderma reesei cellulases

Neutrase, a commercial preparation of Bacillus subtilis, was covalently immobilized on alginate−glutaraldehyde beads. Immobilization conditions and characterization of the immobilized enzyme were investigated. Central composite design and response surface methods were employed to evaluate the effects of immobilization parameters, such as glutaraldehyde concentration, enzyme loading, immobilization pH, and immobilization time. Under optimized working conditions (2% alginate, 6.2% glutaraldehyde, 61.84 U mL−1 Neutrase, pH 6.2, and 60 min) the immobilization yield was about 50%. The immobilized enzyme exhibited higher Km compared to the soluble enzyme. The pH−activity profile was widened upon immobilization. The optimum temperature was shifted from 50 to 60 °C, and the apparent activation energy was decreased from 47.7 to 22.0 kJ mol−1 by immobilization. The immobilized enzyme also showed significantly enhanced thermal stability.

Manuel Perez-Mateos

Papers

Antioxidant properties, radical scavenging activity and biomolecule protection capacity of flavonoid naringenin and its glycoside naringin: a comparative study

Kinetic properties and thermal behaviour of polygalacturonase used in fruit juice clarification

Immobilization of naringinase from Aspergillus niger CECT 2088 in poly(vinyl alcohol) cryogels for the debittering of juices

Kinetics of cellulose saccharification by Trichoderma reesei cellulases

Neutrase Immobilization on Alginate−Glutaraldehyde Beads by Covalent Attachment