Showing papers in "Critical Reviews in Biotechnology in 2010"

Roles of enzymatic and nonenzymatic antioxidants in plants during abiotic stress

Abstract: Reactive oxygen species (ROS) are produced in plants as byproducts during many metabolic reactions, such as photosynthesis and respiration. Oxidative stress occurs when there is a serious imbalance between the production of ROS and antioxidant defense. Generation of ROS causes rapid cell damage by triggering a chain reaction. Cells have evolved an elaborate system of enzymatic and nonenzymatic antioxidants which help to scavenge these indigenously generated ROS. Various enzymes involved in ROS-scavenging have been manipulated, over expressed or downregulated to add to the present knowledge and understanding the role of the antioxidant systems. The present article reviews the manipulation of enzymatic and nonenzymatic antioxidants in plants to enhance the environmental stress tolerance and also throws light on ROS and redox signaling, calcium signaling, and ABA signaling.

β Galactosidases and their potential applications: a review

Abstract: β Galactosidases have been obtained from microorganisms such as fungi, bacteria and yeasts; plants, animals cells, and from recombinant sources. The enzyme has two main applications; the removal of lactose from milk products for lactose intolerant people and the production of galactosylated products. In order to increase their stability, reusability, and use in continuous reactors, these enzymes have been immobilized on both organic and inorganic support via adsorption, covalent attachment, chemical aggregation, microencapsulation, and entrapment. Free and immobilized preparations of β galactosidases have been exploited in various applications such as industrial, biotechnological, medical, analytical, and in different other applications. β galactosidase is widely used in food industry to improve sweetness, solubility, flavor, and digestibility of dairy products. Immobilized β galactosidases are employed for the continuous hydrolysis of lactose from whey and milk in a number of reactors such as hollow fiber reactors, tapered column reactors, packed bed reactors, fluidized bed reactors etc.

Methods for investigating biosurfactants and bioemulsifiers: a review

Abstract: Microorganisms produce biosurfactant (BS)/bioemulsifier (BE) with wide structural and functional diversity which consequently results in the adoption of different techniques to investigate these diverse amphiphilic molecules. This review aims to compile information on different microbial screening methods, surface active products extraction procedures, and analytical terminologies used in this field. Different methods for screening microbial culture broth or cell biomass for surface active compounds production are also presented and their possible advantages and disadvantages highlighted. In addition, the most common methods for purification, detection, and structure determination for a wide range of BS and BE are introduced. Simple techniques such as precipitation using acetone, ammonium sulphate, solvent extraction, ultrafiltration, ion exchange, dialysis, ultrafiltration, lyophilization, isoelectric focusing (IEF), and thin layer chromatography (TLC) are described. Other more elaborate techniques including high pressure liquid chromatography (HPLC), infra red (IR), gas chromatography-mass spectroscopy (GC-MS), nuclear magnetic resonance (NMR), and fast atom bombardment mass spectroscopy (FAB-MS), protein digestion and amino acid sequencing are also elucidated. Various experimental strategies including static light scattering and hydrodynamic characterization for micelles have been discussed. A combination of various analytical methods are often essential in this area of research and a numbers of trials and errors to isolate, purify and characterize various surface active agents are required. This review introduces the various methodologies that are indispensable for studying biosurfactants and bioemulsifiers.

Cellulase activities in biomass conversion: measurement methods and comparison

Abstract: Cellulose, the major constituent of all plant materials and the most abundant organic molecule on the Earth, is a linear biopolymer of glucose molecules, connected by β-1,4-glycosidic bonds. Enzymatic hydrolysis of cellulose requires mixtures of hydrolytic enzymes including endoglucanases, exoglucanases (cellobiohydrolases), and β-glucosidases acting in a synergistic manner. In biopolymer hydrolysis studies, enzyme assay is an indispensable part. The most commonly used assays for the individual enzymes as well as total cellulase activity measurements, including their advantages and limitations, are summarized in this review article. In addition, some novel approaches recently used for enzyme assays are summarized.

Structural determinants of the substrate specificities of xylanases from different glycoside hydrolase families.

Abstract: Xylanases are of widespread importance in several food and non-food biotechnological applications. They degrade heteroxylans, a structurally heterogeneous group of plant cell wall polysaccharides, and other important components in various industrial processes. Because of the highly complex structures of heteroxylans, efficient utilization of xylanases in these processes requires an in-depth knowledge of their substrate specificity. A significant number of studies on the three-dimensional structures of xylanases from different glycoside hydrolase (GH) families in complex with the substrate provided insight into the different mechanisms and strategies by which xylanases bind and hydrolyze structurally different heteroxylans and xylo-oligosaccharides (XOS). Combined with reports on the hydrolytic activities of xylanases on decorated XOS and heteroxylans, major advances have been made in our understanding of the link between the three-dimensional structures and the substrate specificities of these enzymes. In this review, authors gave a concise overview of the structure-function relationship of xylanases from GH5, 8, 10, and 11. The structural basis for inter- and intrafamily variation in xylanase substrate specificity was discussed as are the implications for heteroxylan degradation.

Biorefinery of waste orange peel

Abstract: Up to comparatively recently orange peel and the associated residual remnants of membranes resulting from juice extraction represented a significant disposal problem, especially in those regions where orange cultivation is a major industry. However, recent research has demonstrated that orange peel waste represents a potentially valuable resource that can be developed into high value products. These developments are critically reviewed in this article. This includes a summary of the chemical composition of the substrate and an assessment of the range of applications in which the peel is deployed. Utilization as a substrate to produce animal feed, fertilizer, essential oils, pectin, ethanol, methane, industrial enzymes, and single cell protein is discussed. The applications described together with those that will no doubt be developed in the future, represent great opportunities to harness the economical benefit of this agro-industrial waste and to develop even more efficient and sustainable systems. A scheme of integrated utilization of orange peel in a biorefinery approach is discussed together with some prediction of further necessary research.

A critical review of the application of white rot fungus to environmental pollution control.

Abstract: Research on white rot fungi for environmental biotechnology has been conducted for more than 20 years. In this article, we have reviewed processes for cell growth and enzyme production including the factors influencing enzyme productivity and the methods for enhancement of enzyme production. Significant progress has been achieved in molecular biology related to white rot fungi, especially related to the extraction of genetic material (RNA and DNA), gene cloning and the construction of genetically engineered microorganisms. The development of biotechnologies using white rot fungi for environmental pollution control has been implemented to treat various refractory wastes and to bioremediate contaminated soils. The current status and future research needs for fundamentals and application are addressed in this review.

Biotechnological approaches to develop bacterial chitinases as a bioshield against fungal diseases of plants

Abstract: Fungal diseases of plants continue to contribute to heavy crop losses in spite of the best control efforts of plant pathologists. Breeding for disease-resistant varieties and the application of synthetic chemical fungicides are the most widely accepted approaches in plant disease management. An alternative approach to avoid the undesired effects of chemical control could be biological control using antifungal bacteria that exhibit a direct action against fungal pathogens. Several biocontrol agents, with specific fungal targets, have been registered and released in the commercial market with different fungal pathogens as targets. However, these have not yet achieved their full commercial potential due to the inherent limitations in the use of living organisms, such as relatively short shelf life of the products and inconsistent performance in the field. Different mechanisms of action have been identified in microbial biocontrol of fungal plant diseases including competition for space or nutrients, production of antifungal metabolites, and secretion of hydrolytic enzymes such as chitinases and glucanases. This review focuses on the bacterial chitinases that hydrolyze the chitinous fungal cell wall, which is the most important targeted structural component of fungal pathogens. The application of the hydrolytic enzyme preparations, devoid of live bacteria, could be more efficacious in fungal control strategies. This approach, however, is still in its infancy, due to prohibitive production costs. Here, we critically examine available sources of bacterial chitinases and the approaches to improve enzymatic properties using biotechnological tools. We project that the combination of microbial and recombinant DNA technologies will yield more effective environment-friendly products of bacterial chitinases to control fungal diseases of crops.

Mushroom lectins: Current status and future perspectives

Abstract: Lectins are nonimmune proteins or glycoproteins that bind specifically to cell surface carbohydrates, culminating in cell agglutination. These are known to play key roles in host defense system and also in metastasis. Many new sources have been explored for the occurrence of lectins during the last few years. Numerous novel lectins with unique specificities and exploitable properties have been discovered. Mushrooms have attracted a number of researchers in food and pharmaceuticals. Many species have long been used in traditional Chinese medicines or functional foods in Japan and other Asian countries. A number of bioactive constituents have been isolated from mushrooms including polysaccharides, polysaccharopeptides, polysaccharide–protein complexes, proteases, ribonucleases, ribosome inactivating proteins, antifungal proteins, immunomodulatory proteins, enzymes, lectins, etc. Mushroom lectins are endowed with mitogenic, antiproliferative, antitumor, antiviral, and immunestimulating potential. In this review, an attempt has been made to collate the information on mushroom lectins, their blood group and sugar specificities, with an emphasis on their biomedical potential and future perspectives.

Chymosin and other milk coagulants: sources and biotechnological interventions

Abstract: Calf rennet, which consists of over 90% chymosin, is commonly used in cheese industries for the curdling of milk. Various animal, plant and microbial sources have been exploited as possible alternatives to calf rennet. The coagulating properties of the enzymatic preparations (coagulants) from these sources differ in terms of their physicochemical factors. The cheese industry has always sought out novel and stable enzyme sources, and recombinant chymosin has been found to be an effective alternative since it possesses several advantages over plant and microbial milk-clotting enzymes. This paper reviews the use of various milk coagulants, especially animal coagulants, for cheese making. Advancements in genetic and protein engineering to produce recombinant chymosin are discussed in addition to evaluating its identity to the rennet available from natural sources.

Potential applications of natural origin polymer-based systems in soft tissue regeneration

Abstract: Despite the many advances in tissue engineering approaches, scientists still face significant challenges in trying to repair and replace soft tissues. Nature-inspired routes involving the creation of polymer-based systems of natural origins constitute an interesting alternative route to produce novel materials. The interest in these materials comes from the possibility of constructing multi-component systems that can be manipulated by composition allowing one to mimic the tissue environment required for the cellular regeneration of soft tissues. For this purpose, factors such as the design, choice, and compatibility of the polymers are considered to be key factors for successful strategies in soft tissue regeneration. More recently, polysaccharide-protein based systems have being increasingly studied and proposed for the treatment of soft tissues. The characteristics, properties, and compatibility of the resulting materials investigated in the last 10 years, as well as commercially available matrices or those currently under investigation are the subject matter of this review.

Biotechnological implications from abscisic acid (ABA) roles in cold stress and leaf senescence as an important signal for improving plant sustainable survival under abiotic-stressed conditions.

Abstract: In the past few years, the signal transduction of the plant hormone abscisic acid (ABA) has been studied extensively and has revealed an unanticipated complex. ABA, characterized as an intracellular messenger, has been proven to act a critical function at the heart of a signaling network operation. It has been found that ABA plays an important role in improving plant tolerance to cold, as well as triggering leaf senescence for years. In addition, there have been many reports suggesting that the signaling pathways for leaf senescence and plant defense responses may overlap. Therefore, the objective was to review what is known about the involvement of ABA signaling in plant responses to cold stress and regulation of leaf senescence. An overview about how ABA is integrated into sugars and reactive oxygen species signaling pathways, to regulate plant cold tolerance and leaf senescence, is provided. These roles can provide important implications for biotechnologically improving plant cold tolerance.

Understanding molecular mechanisms for improving phytoremediation of heavy metal-contaminated soils

Abstract: Heavy metal pollution of soil is a significant environmental problem with a negative potential impact on human health and agriculture. Rhizosphere, as an important interface of soil and plants, plays a significant role in phytoremediation of contaminated soil by heavy metals, in which, microbial populations are known to affect heavy metal mobility and availability to the plant through release of chelating agents, acidification, phosphate solubilization and redox changes, and therefore, have potential to enhance phytoremediation processes. Phytoremediation strategies with appropriate heavy metal-adapted rhizobacteria or mycorrhizas have received more and more attention. In addition, some plants possess a range of potential mechanisms that may be involved in the detoxification of heavy metals, and they manage to survive under metal stresses. High tolerance to heavy metal toxicity could rely either on reduced uptake or increased plant internal sequestration, which is manifested by an interaction between a genotype and its environment.A coordinated network of molecular processes provides plants with multiple metal-detoxifying mechanisms and repair capabilities. The growing application of molecular genetic technologies has led to an increased understanding of mechanisms of heavy metal tolerance/accumulation in plants and, subsequently, many transgenic plants with increased heavy metal resistance, as well as increased uptake of heavy metals, have been developed for the purpose of phytoremediation. This article reviews advantages, possible mechanisms, current status and future direction of phytoremediation for heavy-metal-contaminated soils.

Quantum dots synthesis and biological applications as imaging and drug delivery systems

Abstract: Semiconductor quantum dots (QDs) synthesized by metal ions and colloid stabilizers have been explored as promising probes in advanced imaging techniques, tumor diagnostic agents, and drug delivery systems. The ability to modulate QDs surface chemistry through particle—shape control, surface coating, and surface functionalization—has rendered them a valuable tool in biological sciences. The tremendous advances in nanotechnology revealed the unique properties of QD crystals in both in vitro and in vivo conditions. In this review, we summarize the recent trends in QD synthesis, surface modification, and biological applications particularly for cancer targeting and treatment.

Thermophilic anaerobic digestion: the best option for waste treatment.

Abstract: After introducing thermophilic anaerobic digestion (AD), characteristics of thermophilic methanogens are provided. Accordingly, (a) site of occurrence, (b) morphological characteristics (shape and motility), (c) biochemical characteristics (Gram character and % G+C profile), (d) nutritional characteristics (NaCl requirement and substrate specificity), and (e) growth characteristics (pH and temperature) of thermophilic methanogens are described. Some studies of the thermophilic AD are cited with their operational management problems. Subsequently, strategies to maximize net energy production are given, including mode of heating the bioreactors, role of agitation to promote AD performance and mode/intensity of mixing. Finally, advantages as well as drawbacks of AD under thermophilic conditions are given, concluding with its applications.

Alginate as an immobilization material for MAb production via encapsulated hybridoma cells.

Abstract: Alginate has been widely used in various applications since its first extraction. What makes this biopolymer useful is its high biocompatibility and humid gelation conditions. Both of these features bring it into prominence as an ideal immobilization material. However, there are some complicated aspects of cell immobilization using alginate biopolymers. This review discuses and clarifies these crucial points, using as an example the bioprocessing of highly fragile cells (hybridoma cells). The review focuses on the cultivation and production of alginate encapsulated cells.

Innovation in biotechnology: moving from academic research to product development--the case of biosensors.

Abstract: The fast pace of technological change in the biotechnology industry and the market demands require continuous innovation, which, owing to the science base of the sector, derives from academic research through a transformation process that converts science-oriented knowledge to marketable products. There appear to be some inherent difficulties in transforming directly the knowledge output of academic research to industrial use. The purpose of this article is to examine certain transition mechanisms from monodisciplinary academic isolation (curiosity-driven and internal-worth innovation) to university-industry alliances (market-driven and public-worth innovation) through inter-organizational multidisciplinary collaboration and contextualize the analysis with the case of biosensors. While the majority of literature on the subject studies the channels of knowledge transfer as determinants of alliance success (transferor/transferee interactions), either from the university side (science base) or the industry side (market base), this article focuses on the transferable (technology base) and how it can be strategically modeled and managed by the industry to promote innovation. Based on the valuable lessons learnt from the biosensor paradigm, the authors argue that strategic industry choices deal primarily with the best stage/point to intersect and seize the university output, implanting the required element of marketability that will transform an idea to a viable application. The authors present a methodological approach for accelerating the knowledge transfer from the university to industry aiming at the effective transition of science to products through a business model reconfiguration.

Mesophilic anaerobic digestion: first option for waste treatment in tropical regions.

Abstract: Rural India derives its energy needs for cooking and heating through the use of fuel wood and for lighting and agricultural operations through kerosene and diesel. Use of fuel wood has aggravated the problem of de-forestation, while availability of kerosene and diesel cannot be guaranteed due to corrupt practices in the public distribution systems. In contrast, urban India derives its energy needs through LPG cylinders, petrol, and electricity. However, their cost and uncertainty rendered them beyond the reach of lower income population. This scenario is more or less true with many developing countries. To meet these objectives, biogas generation from biodegradable waste using anaerobic digestion (AD) appears to be a sustainable avenue as it could be used for (a) water and space heating of farmhouses, animal shelters, (b) generating steam for food processing plants, and (c) electricity generation, in addition to reducing the pollution/hazard potential of these wastes. Many of the underdeveloped and developing countries are in the temperate zone and thus mesophilic AD could provide a desired pathway to achieve a long delayed need of energy for comfortable living, farming, and industrial operations. Efforts made in this direction are reviewed in the present article.

Germplasm-regression-combined (GRC) marker-trait association identification in plant breeding: a challenge for plant biotechnological breeding under soil water deficit conditions

Abstract: In the past 20 years, the major effort in plant breeding has changed from quantitative to molecular genetics with emphasis on quantitative trait loci (QTL) identification and marker assisted selection (MAS). However, results have been modest. This has been due to several factors including absence of tight linkage QTL, non-availability of mapping populations, and substantial time needed to develop such populations. To overcome these limitations, and as an alternative to planned populations, molecular marker-trait associations have been identified by the combination between germplasm and the regression technique. In the present preview, the authors (1) survey the successful applications of germplasm-regression-combined (GRC) molecular marker-trait association identification in plants; (2) describe how to do the GRC analysis and its differences from mapping QTL based on a linkage map reconstructed from the planned populations; (3) consider the factors that affect the GRC association identification, including selections of optimal germplasm and molecular markers and testing of identification efficiency of markers associated with traits; and (4) finally discuss the future prospects of GRC marker-trait association analysis used in plant MAS/QTL breeding programs, especially in long-juvenile woody plants when no other genetic information such as linkage maps and QTL are available.