Received: 4 May, 2011. Accepted: 7 February, 2012. Invited Review Dynamic Biochemistry, Process Biotechnology and Molecular Biology ©2012 Global Science Books Lipase Production in Solid-State Fermentation (SSF): Recent Developments and Biotechnological Applications Ashok Kumar • Shamsher Singh Kanwar * Department of Biotechnology, Himachal Pradesh University, Summer Hill, Shimla-171 005, India Corresponding author: * kanwarss2000@yahoo.com ABSTRACT Lipases are the most widely used biocatalysts, because they can catalyze several unnatural and remarkable reactions in non-aqueous media, such as bio-fuel production, production of value-added products such as esters, organic acids, food, beverage, cosmetics and pharmaceutical materials. Solid-state fermentation (SSF) represents an interesting alternative to produce industrial enzymes at lower costs due to the possibility of using inexpensive agro-industrial residues as culture media. This review aims to explore various agriculture by- products like husk, straw, agricultural raw materials, waste of the oil industry, among others that are locally available and are also cost- effective requiring low nutrient supplementation to produce microbial lipase(s) in SSF. Enzyme production is associated with the growth of the bacterial culture. The physico-chemical fermentation parameters such as pH of the medium, moisture content, particle-size, nature of particles and microbial inoculum level play crucial role(s) in lipase production. SSF has gained renewed interest and fresh attention of researchers to develop processes to achieve large-scale enzyme production by solid waste treatment and in its application in the industry to synthesize the products of commercial value. _____________________________________________________________________________________________________________ Keywords: agricultural raw material, biofuel production, lipases, solid-state fermentation Abbreviations: ANN, ANOVA; aw, water activity; DAG, diacyl glycerol; EVOP, Evolutionary operation; MAG, monoacyl glycerol; RSM, response surface methodology; SmF, submerged state fermentation; SSF, solid state fermentation CONTENTS INTRODUCTION........................................................................................................................................................................................ 13 ADVANTAGES OF SOLID STATE FERMENTATION ............................................................................................................................. 15 CLASSIFICATION OF SUBSTRATES FOR SSF ...................................................................................................................................... 16 METHODS OF PRODUCTION OF LIPASE ON SOLID SUBSTRATUM ............................................................................................... 16 FACTORS AFFECTING THE PRODUCTION OF LIPASE IN SSF.......................................................................................................... 18 BIOTECHNOLOGICAL APPLICATIONS ................................................................................................................................................. 21 CONCLUSION ............................................................................................................................................................................................ 23 ACKNOWLEDGEMENTS ......................................................................................................................................................................... 24 REFERENCES............................................................................................................................................................................................. 24 _____________________________________________________________________________________________________________ INTRODUCTION Solid-state fermentation (SSF) is a valuable technique for utilization of agro-industrial by-products to produce value added product(s) of commercial interest. SSF is defined as any fermentation process performed on a non-soluble mate- rial that acts both as physical support as well as source of nutrients in absence of free flowing liquid (Pandey 1992). The technique involves inoculation and growth of microbes on porous particulate solid substrate maintaining low mois- ture content. The water content and nutrients present in the substrate support the growth of microorganisms and the organisms secrete useful enzymes while growing on solid substrate (Pandey et al. 2003). Lipases an interesting class of acyl hydrolases (E.C. 3.1.1.3) has been in the centre stage of bio-catalytic reactions as they are naturally en- dowed with the potential to retain bio-catalytic activity in both aqueous as well as organic media. Lipases are ubiqui- tous in nature and are produced by various animals and most of the microorganisms. Lipases of microbial origin, mainly bacterial and fungal represent the most widely used class of enzymes in biotechnological applications and organic chemistry. A large number of lipases have been screened for their use as food additives (flavour modifying enzymes), industrial reagents (glyceride hydrolyzing en- zyme), stain removers (detergent additives), digestive drugs, diagnostic enzymes in medical applications, neutraceuticals, surfactants and additives in cosmetics (Verma and Kanwar 2010). The conventional reactions performed by lipases in aqueous media are often referred as hydrolysis; release of alcohol and corresponding fatty acid(s) molecules during enzymatic action on substrates such as glycerol or similar esters (Fig. 1). These reactions are indispensable for the bioconversion of lipids (triacylglycerol) and usually pro- ceed with higher regio- and/or enantio-selectivity. However, the reverse reaction referred as esterification that could be efficiently achieved in organic media/water restricted con- ditions (organic solvents or non-ionic fluids) involves the formation of an ester along with water molecules as by- product of such reactions. Microbial lipases show a broad spectrum of industrial applications due to their greater sta- bility, substrate specificity and lower production cost when compared to other sources. Additionally, an enormous bio- diversity of microorganisms improves alternative biotech- nological processes and justifies the search for new lipases. Filamentous fungi are often recognized as the best lipase ®