Esterase plays a major role in the degradation of natural materials and industrial pollutants, viz., cereal wastes, plastics, and other toxic chemicals. It is useful in the synthesis of optically pure compounds, perfumes, and antioxidants. The potential applications of esterase with reference to agriculture, food, and pharmaceutical industries, are discussed in this review. Promising applications in this avenue can be supported by appropriate production strategies.

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Chitin, a homopolymer of N-acetylglucosamine, is obtained from a variety of sources. They form the structural component of fungal cell wall and plants. They are commercially obtained from shrimp and crab shell waste from the ®shing industry. Recent advances in understanding the structure and properties of chitin and its derivatives has opened a lot of new avenues for its applications. Improvements in the properties of chitin for a particular application can be easily brought about by chemical modi®cations. The applicability of chitin in many areas and its easy manipulation has resulted in a considerable amount of research being done on the possible applications of chitinase.

Filamentous fungi comprise an industrially very important collection of microorganisms, since they are used for the production of a wide variety of products ranging from primary metabolites to secondary metabolites and further on to industrial enzymes (such as proteases, lipases and antibiotics). It is known that fungal morphology is often considered as one of the key parameters in industrial production. For the production of fungal metabolite products, the desired morphology varies from one product to another. Many parameters affect the morphology of fungi during the process of fermentation, among them speed of agitation, speci®c growth rate, dissolved oxygen, number of spores or conidia per liter of fermentation broth are important and should be considered when higher yield is desired in the process. It is, therefore, of considerable importance to understand the mechanism underlying the morphology of the cell, its growth and product formation by ®lamentous fungi. Such knowledge may be used in the optimization of the microbial process. Several literatures with various fungi to study their morphology, relating enzyme or product production to the character of the fungi in the study is reviewed. It is also considered that how the process parameters affects the morphology. The aim of this communication is to review the relevant literature to understand the morphology of ®lamentous fungi. List of symbols bhyphal density, lm/tip D i impeller diameter, m D pellet diameter (in Eqs. 4 and 5), mm D r dilution rate, h )1 k constant, number of section used for branching (in Eq. 7) K c constant K r constant (in Eq. 5) K r linear colony radial growth rate (in Eq. 1), lm/h L e mean length of main hyphae, lm L e *mean dimensionless length, lm L t mean total length of hyphae, lm L hgu mean length of hyphal growth unit, lm M 0 dry weight of mycelia at time t 0 , g M 1 dry weight of mycelia at time t 1 , g n number of disrupted pellets N impeller speed, h )

A range of chitinase genes from microorganisms have been cloned and the potential uses of these genetically manipulated organisms are being investigated by various researchers. Fungi and yeast are better producers of chitinase than bacteria. Since fungi grow at a slower rate, there have been efforts to clone the fungal chitinase genes into fast-growing bacteria. This review gives a brief survey of recent progress in the regulation and cloning of microbial chitinase genes. Emphasis is placed on the post-translational modification and localization of the recombinant protein in the host. Various amino acid domains are present in this protein. The mode of catalytic activity of the recombinant protein in comparison to the wild-type protein is discussed in the available literature. The different mechanisms involved in the regulation of chitinase genes from various microorganisms is discussed by the researchers. The scope of future research and conclusions yet to be obtained in this particular area are also outlined in this review.

Metal nanoparticles have unique optical, electronic, and catalytic properties. There exist well-defined physical and chemical processes for their preparation. Those processes often yield small quantities of nanoparticles having undesired morphology, and involve high temperatures for the reaction and the use of hazardous chemicals. Relatively, the older technique of bioremediation of metals uses either microorganisms or their components for the production of nanoparticles. The nanoparticles obtained from bacteria, fungi, algae, plants and their components, etc. appear environment-friendly, as toxic chemicals are not used in the processes. In addition to this, the formation of nanoparticles takes place at almost normal temperature and pressure. Control of the shape and size of the nanoparticles is possible by appropriate selection of the pH and temperature. Three important steps are the bioconversion of Ag+ ions, conversion of desired crystals to nanoparticles, and nanoparticle stability. Generally, nanoparticles are characterized by the UV-visible spectroscopy and use of the electron microscope. Silver nanoparticles are used as antimicrobial agents and they possess antifungal, anti-inflammatory, and anti-angiogenic properties. This review highlights the biosynthesis of silver nanoparticles by various organisms, possible mechanisms of their synthesis, their characterization, and applications of silver nanoparticles.

There are many approaches available for introducing foreign DNA into eukaryotes and prokaryotes. The most commonly used technique and currently of more practical interest is the electroporation. This review will focus on the electroporation as a promising, highly efficient and effective means of gene transfer. We summarize a detailed assessment of the various parameters and conditions that govern electroporation of a wide range of cell types.

Extractive fermentation in aqueous two-phase systems is a meaningful approach to overcome low product yield in a conventional fermentation process, and by proper design of the two-phase system it is possible to obtain the product in a cell-free stream. The characteristics of an aqueous two-phase system, various polymers used for forming an aqueous two-phase system, the physicochemical parameters of the aqueous two-phase system, partitioning of biomolecules and cell mass and the effect of individual phase forming polymers on cell growth and product formation are reviewed in this article. The various extractive fermentation processes are also summarised here. At the end, the economic viability and scope of aqueous two-phase fermentation are briefly discussed in relation to the wider application of this topic.