TurnerPmicrobialfactory - Microbial Cell Factories Review...

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Bio Med Central Page 1 of 23 (page number not for citation purposes) Microbial Cell Factories Open Access Review Potential and utilization of thermophiles and thermostable enzymes in biorefining Pernilla Turner, Gashaw Mamo and Eva Nordberg Karlsson* Address: Dept Biotechnology, Center for Chemistry and Chemical Engineering, Lund University, P.O. Box 124, SE-221 00 Lund, Sweden Email: Pernilla Turner - pernilla.turner@biotek.lu.se; Gashaw Mamo - gashaw.mamo@biotek.lu.se; Eva Nordberg Karlsson* - eva.nordberg_karlsson@biotek.lu.se * Corresponding author Abstract In today's world, there is an increasing trend towards the use of renewable, cheap and readily available biomass in the production of a wide variety of fine and bulk chemicals in different biorefineries. Biorefineries utilize the activities of microbial cells and their enzymes to convert biomass into target products. Many of these processes require enzymes which are operationally stable at high temperature thus allowing e.g . easy mixing, better substrate solubility, high mass transfer rate, and lowered risk of contamination. Thermophiles have often been proposed as sources of industrially relevant thermostable enzymes. Here we discuss existing and potential applications of thermophiles and thermostable enzymes with focus on conversion of carbohydrate containing raw materials. Their importance in biorefineries is explained using examples of lignocellulose and starch conversions to desired products. Strategies that enhance thermostablity of enzymes both in vivo and in vitro are also assessed. Moreover, this review deals with efforts made on developing vectors for expressing recombinant enzymes in thermophilic hosts. Background Thermostable enzymes and microorganisms have been topics for much research during the last two decades, but the interest in thermophiles and how their proteins are able to function at elevated temperatures actually started as early as in the 1960's by the pioneering work of Brock and his colleagues [1]. Microorganisms are, based on their optimal growth temperatures, divided into three main groups, i.e . psychrophiles (below 20°C), mesophiles (moderate temperatures), and thermophiles (high tem- peratures, above 55°C) [2]. Only few eukaryotes are known to grow above this temperature, but some fungi grow in the temperature range 50 – 55°C [3]. Several years ago Kristjansson and Stetter [4], suggested a further divi- sion of the thermophiles and a hyperthermophile bound- ary (growth at and above 80°C) that has today reached general acceptance. Most thermophilic bacteria character- ised today grow below the hyperthermophilic boundary (with some exceptions, such as Thermotoga and Aquifex [5]) while hyperthermophilic species are dominated by the Archaea.
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This note was uploaded on 07/19/2010 for the course BME 3604 taught by Professor Lt during the Spring '10 term at University of Florida.

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TurnerPmicrobialfactory - Microbial Cell Factories Review...

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