Rastall Novel Enzyme Technology for Food Applications

1. Auflage 2007
ISBN: 978-1-84569-371-8
Verlag: Elsevier Science & Techn.
Format: EPUB
Kopierschutz: 6 - ePub Watermark

E-Book, Englisch, 336 Seiten

Reihe: Woodhead Publishing Series in Food Science, Technology and Nutrition

The food industry is constantly seeking advanced technologies to meet consumer demand for nutritionally balanced food products. Enzymes are a useful biotechnological processing tool whose action can be controlled in the food matrix to produce higher quality products. Written by an international team of contributors, Novel enzyme technology for food applications reviews the latest advanced methods to develop specific enzymes and their applications.Part one discusses fundamental aspects of industrial enzyme technology. Chapters cover the discovery, improvement and production of enzymes as well as consumer attitudes towards the technology. Chapters in Part two discuss enzyme technology for specific food applications such as textural improvement, protein-based fat replacers, flavour enhancers, and health-functional carbohydrates.Novel enzyme technology for food applications is a standard reference for all those in industry and academia concerned with improving food products with this advanced technology. - Reviews the latest advanced methods to develop specific enzymes - Discusses ways of producing higher quality food products - Explores the improvement and production of enzymes

Autoren/Hrsg.

Rastall, R.

Leseproben

1

Discovering new industrial enzymes for food applications

Thomas Schäfer,     Novozymes A/S, Denmark

Publisher Summary

This chapter presents that enzymes have been exploited by humans for thousands of years. Traditional foods and beverages, as well as paper and textiles were produced with the help of enzymes that were present in starting materials as early as 6000 BC in China, Sumer and Egypt. The epoch of classical biotechnology was marked by the landmark discoveries of microbes by Antonie van Leeuwenhook, of fermentations as biological processes by Louis Pasteur, of enzymes as proteins by Eduard Buchner and of the first enzyme crystal structures by James B. Sumner. Nature holds a wonderful diversity of organisms and the corresponding wealth of enzymes and has often been the starting point for the identification of novel enzymes. For a variety of applications, even nature’s assortment faces some limitations or it is too time-consuming and difficult to look into nature’s diversity. It imposes a challenge for scientists to optimize existing natural enzymes and to generate additional “artificial” diversity to tailor-make enzymes for a given application. Natural diversity approaches and optimization strategies are complementary routes and both are equally important in developing a high-quality diversity of enzymes.

1.1 Introduction

Enzymes have been exploited by humans for thousands of years. Traditional foods and beverages like cheese, yoghurt and kefir, bread, beer, vinegar, wine and other fennented drinks, as well as paper and textiles, were produced with the help of enzymes which were present in starting materials as early as 6000 BC in China, Sumer and Egypt. The epoch of classical biotechnology was marked by the landmark discoveries of microbes by Leeuwenhook, of fennentations as biological processes by Pasteur, of enzymes as proteins by Buchner and of the first enzyme crystal structures by Sumner.

The modem era of industrial enzymology began in 1913 when Otto Rohm was granted a patent for the use of a crude protease mixture isolated from pancreases in laundry detergents. In the following years an increasing number of enzymes were found in microorganisms and these microbes were cultured in large scale fennentations to produce enzymes. However, the number of enzymes that could be produced in this fashion was limited, because not all microbes are amenable to large scale fermentation. The pioneering work of Avery and MacLeod, Hershey and Chase, Watson and Crick, Cohen and Boyer and many others who introduced the era of recombinant biotechnology revolutionized industrial enzyme screening and production.

With the advent of genetic engineering, genes encoding interesting enzymes could be transferred to and expressed in selected host microbes for production on an industrial scale. Today, gene technology plays a major role in both the discovery of novel enzymes and the optimization of existing proteins, and is basis for the production of the majority of industrial enzymes. Food applications of enzymes represent a wide and highly diverse field including baking, dairy, juice, vegetable processing and meat. The enzymes are used to obtain a number of benefits, like more efficient processes, leading to reduced use of raw materials, improved or consistent quality, replacement of chemical food additives and avoidance of potential harmful by-products in the food.

1.1.1 Technologies for discovery of industrial enzymes

Nature holds a wonderful diversity of organisms and the corresponding wealth of enzymes and has often been the starting point for the identification of novel enzymes. For a variety of applications even Nature’s assortment faces some limitations or it is too time consuming and difficult to look into Nature’s diversity. This imposes a challenge for scientists to optimize existing natural enzymes and to generate additional ‘artificial’ diversity to tailor-make enzymes for a given application. Natural diversity approaches and optimization strategies are complementary routes and both are equally important in developing a high-quality diversity of enzymes (Nedwin 2005).

Today, discovery of enzymes for the food industry is not only a multidisciplinary effort involving a wide array of different screening technologies, but is also based on close interaction between food scientists who understand or model the application and biotechnologists who can deliver enzymes for initial trials. Each screening project is new and challenging. Accordingly, each project needs to be uniquely designed to solve the specified application problems in a certain industrial application and for each project the expert team needs to have members with exactly the competencies needed to find a solution. It is obvious that major enzyme companies have to master a variety of technologies which, often in combination with each other, lead to the solution. For all approaches it is important to stress that it is not the broadest possible diversity, but rather the highest possible quality of diversity which will lead to the ultimate goal, namely a novel product that addresses exactly the specific demands of the industrial application. In this respect selection/ deselection via perfectly designed assays is of utmost importance, indicating the significance of linking process understanding to biochemistry.

1.2 Where to screen for new enzymes

One of the main questions which has to be answered in the very beginning of each discovery initiative is ‘where to look for diversity?’ (Bull 2000; Fig. 1.1). There are various potential sources, as input to screening programs is basically divided into (a) natural enzyme diversity and (b) artificial diversity, which are comprehensively reviewed by Schäfer and Borchert (2004) and Aehle (2004). Here the basic principles will be summarized.

Fig. 1.1 Overview of the main approaches to diversity input in screening programs.

1.2.1 Nature’s diversity: an unlimited source of enzymes

The challenge is that Nature’s diversity is virtually infinite and that living microorganisms have inhabited virtually all ecological niches on planet Earth during 3.5 billion years of evolution. The number of described bacterial and fungal species is huge, new isolations are added daily so that the actual number can only be extrapolated roughly. From bioinformatics analysis of the genomes it can be assumed that a bacterial genome on average contains about 4000 enzyme coding genes, while for fungi the number of enzyme encoding genes can be up to 20,000 (Hirose ., 2000; Dunn-Coleman and Prade, 1998). The art of screening obviously consists of having the right tools to find the ‘needle’ in this ‘haystack’ of biodiversity; no scientist will start looking into the totally available biodiversity, but will look into groups of carefully selected microorganisms. Considering these numbers and using best practice, it is obvious that all screening efforts face a limitation in that we are only scratching the surface. Microorganisms, namely bacteria, fungi and archaea, which are normally stored in culture collections of the groups performing the screening or in public collections, where the strains are accessible for everyone who is interested, often comprise the biological starting material.

On top of the cultivated diversity, complex gene libraries compiled from natural material without prior cultivation (Handelsman, 2005) can be generated and used to discover industrial enzymes (Short, 1997) and other natural compounds (Brady 2001). Today, it is generally accepted that only minor numbers among the whole of the microbial diversity have been cultured or might even be amenable to growth in the laboratory (Torsvik , 2002) thereby leaving not only a huge set of questions concerning our understanding of the role of microbes in their habitats, but also an enormous potential for yet undiscovered physiological and biochemical traits including enzyme genes in the so-called metagenome (Lorenz and Schleper, 2002; Rondon 1999). It is estimated that 1 g of soil contains more than 4000 different bacterial genomes, that is about 16 million enzyme encoding genes. By isolating the genetic material, be it DNA or RNA, directly from the soil and cloning this into suitable host complexes, ‘environmental libraries’ can be constructed. These gene libraries need to be screened as described below using either sequencebased techniques or activity assays including some novel constraints caused by the complexity of the library.

1.2.2 Bioinformatics and genomics

Input to screening efforts can also come from genes or genomes described by researchers worldwide over time. The updated status of established genomes and those underway can be obtained by visiting the homepage of the TIGR institute (http://www.tigr.org/) or the homepage of the DOE Joint Genome Institute (http://genome.jgi.org/). The use of existing gene infonnation can potentially...