Microbial Production of Food Ingredients, Enzymes and Nutraceuticals

Brian McNeil, David Archer, Ioannis Giavasis, Linda Harvey

• Publisher: Woodhead Publishing
• Year: 2013
• Print ISBN: 9780857093431
• eBook ISBN: 9780857093547
• Topic: Technology & Engineering
• Subtopic: Food Science
• Index: Technology & Engineering

Bacteria, yeast, fungi and microalgae can act as producers (or catalysts for the production) of food ingredients, enzymes and nutraceuticals. With the current trend towards the use of natural ingredients in foods, there is renewed interest in microbial flavours and colours, food bioprocessing using enzymes and food biopreservation using bacteriocins. Microbial production of substances such as organic acids and hydrocolloids also remains an important and fast-changing area of research. Microbial production of food ingredients, enzymes and nutraceuticals provides a comprehensive overview of microbial production of food ingredients, enzymes and nutraceuticals.Part one reviews developments in the metabolic engineering of industrial microorganisms and advances in fermentation technology in the production of fungi, yeasts, enzymes and nutraceuticals. Part two discusses the production and application in food processing of substances such as carotenoids, flavonoids and terponoids, enzymes, probiotics and prebiotics, bacteriocins, microbial polysaccharides, polyols and polyunsaturated fatty acids.Microbial production of food ingredients, enzymes and nutraceuticals is an invaluable guide for professionals in the fermentation industry as well as researchers and practitioners in the areas of biotechnology, microbiology, chemical engineering and food processing.- Provides a comprehensive overview of microbial flavours and colours, food bioprocessing using enzymes and food biopreservation using bacteriocins- Begins with a review of key areas of systems biology and metabolic engineering, including methods and developments for filamentous fungi- Analyses the use of microorganisms for the production of natural molecules for use in foods, including microbial production of food flavours and carotenoids

1

Bioprocessing as a route to food ingredients: an introduction

B.J.B. Wood, University of Strathclyde, UK

Abstract:

The earliest bioprocessing, although not understood as such at the time, was producing foods and fermented beverages. The processes were essentially artisan in nature. They must have begun at village level and such processes are still found in developing countries. Developments in societies’ complexity drove the establishment of more organised production and marketing, which in turn encouraged process standardisation and more uniform and reliable products. Although food and beverages were the principal products, the methods for producing them also resulted in technical materials such as acetic acid, ethanol and lactic acid being manufactured. The early development of microbiology was intimately linked with food and beverage industrialisation, as well as the drive to understand the nature of diseases. Today the biotechnological industries encompass many organism types, vast resources and enormous product diversity. The shift from fossil materials to renewables will both drive further innovation in biotechnology and increase the scope for its products’ applications, for example, polymerised lactic acid as a replacement for petrochemical polymers. Often these ‘substitutes’ offer additional advantages, such as easy biodegradation. The future for bioprocessing in food ingredient production, but also in the wider industrial sphere, is very bright. Fully developing it may require an interesting fusion of modern technologies such as stirred tank reactor fermentors with reinvented and modernised versions of ancient technologies such as solid substrate (koji) fermentations. This book demonstrates the potential and actual developments across the biotechnological spectrum.

Key words

alcoholic beverage production

oriental food fermentations

prebiotics

probiotics and neutraceuticals

solid substrate fermentation

stirred tank reactors

1.1 Food fermentation as an ancient technology: an overview

1.1.1 Fermentation for food modification and conservation

We cannot know when food fermentation began, but all known cultures use it to modify and/or conserve foods. By their very nature most food products are intrinsically unstable, under attack from enzymes present in them as a result of their production, and by the many microbes and other organisms present in the foodstuff’s environment, eager to feast on this food resource. Even those few that are relatively stable, such as seeds, are only relatively so, and in exchange for this enhanced storage time, these tend to be fairly unappetizing unless cooked or otherwise modified. Even hunter-gatherers, at the start of human culture, accustomed though they were to the feast- then-famine lifestyle that was the inevitable outcome of that existence, must surely have sought methods to save any excess food from the hunt for another day.

When the first human settlements began, presumably as simple agriculture developed (although recent excavations in Turkey [see .Norenzayan, 2012] suggest that some form of settlement, at least for religious functions, may have preceded agricultural cultivation), the need to store harvests, plant or animal, must have become essential for settled groups to function. The first human settlements preceded developments such as writing or other means for recording information, indeed this was probably one of the driving forces in inventing recording methods for even such basic things as noting crop yields, and its inevitable consequence, calculating the portion to be grabbed by the ruling classes. Thus we cannot know how humans came to realise that some of the same agents that destroy foods can also act to conserve and improve them.

The understanding that microbes exist, obey biological laws and can be used in a controlled way, are essentially outcomes of our development of the scientific method. That is not to say that our remote ancestors did not see such things as the mycelium that developed as a mould overgrew a food item, or the yeast mass that developed as a wine or beer underwent fermentation. However, it is far less certain that they understood that these were living things, indeed the ‘vitalist’ and other arguments over (for example) yeast’s nature and its mode of action, were still matters for heated debate until well into the 19th century.

1.1.2 Microbial production of industrial chemicals as well as food ingredients

Our primary focus here is on microbial activities in their roles connected with foods, although this is in some ways an artificial distinction. Microbes’ roles in generating a range of products important in manufacturing and other activities are essentially indistinguishable from their directly food- related functions. For example, consider ethanoic (acetic) acid. This still has many technological applications in addition to its food flavouring and preserving uses. Today these industrial uses are largely met by synthetic, petrochemically derived product, although I have visited a substantial manufactory in Indonesia where sugar cane molasses are fermented to ethanol and then distilled to a high purity product and catalytically oxidised to ethanoic acid, yielding three product streams (ethanol, ethanoic acid and ethyl ethanoate) for the Japanese electronics industry. In fact ethanoic acid has been produced by fermentation for millennia and its manifold applications in medicine, manufacturing, pigment production, and so on developed and have evolved over these millennia.

The same is true for other organic acids, particularly lactic acid, while yet other acids, traditionally derived exclusively from plant resources (such as citric acid), are required in such vast amounts today that it has become essential to develop fermentations to meet this ever-expanding demand, these acids being too complex for synthetic routes from petrochemicals to be economically viable up to the present time. Lactic acid is a particularly illuminating example here. Apart from its many food and beverage applications, it has always had industrial uses. Traditionally these were met by fermentation production. Latterly, petrochemical manufacture became important. Now, with the development of biodegradable polymers for various applications, not least as plastic shopping bags, there is a huge revival in production by fermentation, driven in substantial part by the need for a single optical isomer to enable polymer strands to be synthesized. An example of this is the big investment in Thailand based on fermentation production from that country’s extensive carbohydrate resources. Although there must be concerns that competition for these resources will increase prices paid for staple energy foods by the country’s poorest inhabitants, there are certain to be positive impacts on employment and export earnings. Thus in this case there is a reversion to traditional production for good economic reasons. Such developments must, however, be considered on a case-by-case basis, and there can be no general rule, either that petrochemical production will supplant fermentation, or that the opposite will be the case.

Another interesting non-food application of microbes is in pigment production. For example, dyes from lichens played an important role in supplying the rich colours essential for dyeing the wool that was then woven into traditional Scottish tartans. Lichens grow only slowly, their being symbioses between cyanobacteria (or sometimes algae) and filamentous fungi, and were adapted to grow in rigorous conditions unsuited for most life forms. Thus, traditional dyeing was unsustainable as markets for Scottish traditional clothing items grew and these pigments have been largely supplanted by azo and other synthetic dyes. Lichens are notoriously difficult to study in the laboratory and academic study of them is generally in serious decline, but there is an active group still working with them in Thailand’s Ramkhamhaeng University. One line of enquiry is determining what conditions impel the fungal partner in the lichen to activate the sites of DNA that encode the enzymes responsible for synthesising the complex pigment molecules. This should eventually supply a deeper understanding of how the symbiosis works, why the pigments are produced and, it is to be hoped, how to operate fermentation to generate the pigments on an economically viable scale.

The foregoing discussion is an idiosyncratic and superficial glance at a complex subject. Subsequent sections of this chapter will consider some of the issues raised in a little more detail, but a true in-depth examination of the issues will be left to the individual chapters that comprise this treatise. It is this author’s commission to set the scene within which subsequent chapters will combine to generate a compelling argument that microbial options for producing food ingredients, enzymes and nutraceuticals have a major part to play in developing a food industry that is fit for purpose in the 21st century. In this connection it is essential to appreciate that, for such developments to be economically viable it is vital to think beyond narrowly food-orientated applications and see that processes originally derived from (often) traditional methods will have commercial non-food applications. It has been suggested, for example by the late John Bu’lock (personal communication) that around the late 1940s the leading industrial nations had to decide between relying on traditional fermentation to generate industrial organic feedstocks and supplanting them with petrochemical products. At the time the choice was driven by simple economics; cheap petrochemical feedstocks and highly reliable chemical engineering processes that easily scaled up to vast outputs meant that fermentation could not compete, so fermentation was confined to specialist food applications where chemical technology was not applicable. Now, as petrochemical stocks are seen to be seriously limited, while demand for products and intermediates traditionally supplied by fermentations inexorably rises, it is salutary to look back to the middle of last century and the 3rd edition of Prescott and Dunn’s Industrial Microbiology (Prescott and Dunn, 1959) and realise what an extraordinary range of essential materials can be generated by fermentation, although we now have to factor in the fact that currently some of the feedstocks for these processes are also human and farm animal foods, posing the risk that a return to heavy reliance on fermentations will impact adversely on food and feed prices.

1.2 Solid substrate fermentations (SSF) and stirred tank reactor (STR) technology: relative industrial dominance

As inspection of the six editions of Prescott and Dunn’s work will demonstrate, SSF was the preferred option for many industrial fermentations until the 1940s. Certain processes, notably ethanol and lactic acid production, but also procedures such as acetone-butanol fermentations, were liquid processes, and enzyme production and most other procedures reliant on filamentous fungi were derived from koji processes associated with traditional products such as soy sauce and rice wine. Even citric acid fermentation was effected by mould growing as a felt of mycelium floating on a thin layer of growth medium. The initial production of penicillin for the battlegrounds of the Second World War was also conducted in this manner, although despite commandeering milk bottles, hospital urine bottles and bedpans, and finally the designing of ‘penicillin’ flasks, it was evident that the heavy demand for penicillin G could not be met in this way. This is generally regarded as the start of the drive to use filamentous fungi in STR growth. This has been so successful that even fermentation for citric acid has finally been coerced into STR, although the very special conditions needed to divert the mould’s metabolism into overproducing the acid meant that this was a particularly difficult feat.

Was the early reliance on SSF just inertial, following on from ancient and successful technologies? Was it really unreasonable to expect STR methods to develop easily? Very few moulds grow suspended in a water column in nature and those that do are mostly highly specialised organisms that have no current commercial interest. Commercially important organisms are isolated from environments where they are growing on leaf litter, rotting fruit and other vegetation, in the soil, and so on. All of these are essentially SSF situations. This means that the interesting organisms are not adapted to growing suspended in liquid. Indeed from their perspective this habitat, particularly when we add in the stresses, mechanical and otherwise, required to achieve optimal mixing and aeration, must seem rather hostile, and so it may be seen as rather remarkable that STR technology is so dominant now. All experience suggests that these fungi want to grow attached to something and everyone who has operated an STR growing them is acutely aware that they will anchor themselves to any attachment points that are available, even the stirrer paddles, on occasion, despite the shear forces operating there.

1.2.1 The case of vinegar production using bacteria

It should be appreciated that these considerations, although most evident for fungal fermentations, are more generally applicable, even to bacteria. Consider vinegar production. The most ancient methodologies, culminating in the Orleans Vinegar Process, depended on a film of vinegar bacteria forming on the surface of an unstirred body of alcoholic liquid, the vinegar bacteria being bound together by a slimy cellulosic exopolysaccharide layer exuded by the bacteria. The process, although slow, inefficient in terms of productive capacity and hence expensive to run, is still preferred for the finest culinary wine vinegar because it is considered to produce the best vinegar in terms of flavour and overall organoleptic quality. However, vinegar has many uses, medicinal, as a food preservative, as a sanitizing agent and antimicrobial, and as the source of ethanoic acid for industrial applications before the petrochemical era, to quote the more obvious examples. Thus the Industrial Revolution vastly increased demand for vinegar and it became evident that traditional methods were inadequate to meet that demand.

In response to this the ‘Quick’ process was developed to generate vinegar in a shorter time span and with considerably increased control over how the process operated. Essentially the apparatus for this process comprises a tower packed with a support medium (classically beech or birch twigs or shavings, these woods being chosen because they do not taint the vinegar with resins or other odour-donating...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Contributor contact details
• Woodhead Publishing Series in Food Science, Technology and Nutrition
• Foreword
• Chapter 1: Bioprocessing as a route to food ingredients: an introduction
• Part I: Systems biology, metabolic engineering of industrial microorganisms and fermentation technology
• Part II: Use of microorganisms for the production of natural molecules for use in foods
• Index