21st Century Guidebook to Fungi, SECOND EDITION, by David Moore, Geoffrey D. Robson and Anthony P. J. Trinci

Table of Contents

1. Chapter 16: Fungi as pathogens of animals, including man
2. Chapter 17: Whole organism biotechnology
   1. Fungal fermentations in submerged liquid cultures
   2. Culturing fungi
   3. Oxygen demand and supply
   4. Fermenter engineering
   5. Fungal growth in liquid cultures
   6. Fermenter growth kinetics
   7. Growth yield
   8. Stationary phase
   9. Growth as pellets
   10. Beyond the batch culture
   11. Chemostats and turbidostats
   12. Uses of submerged fermentations
   13. Alcoholic fermentations
   14. Citric acid biotechnology
   15. Penicillin and other pharmaceuticals
   16. Enzymes for fabric conditioning and processing, and food processing
   17. Steroids and use of fungi to make chemical transformations
   18. The Quorn fermentation and evolution in fermenters
   19. Production of spores and other inocula
   20. Natural digestive fermentations in herbivores
   21. Solid state fermentations
   22. Digestion of lignocellulosic residues
   23. Bread; the other side of the alcoholic fermentation equation
   24. Cheese and salami manufacture
   25. Soy sauce, tempeh and other food products
   26. Chapter 17 References and further reading
   27. Buy a PDF of Chapter 17
3. Chapter 18: Molecular biotechnology

17.16 Enzymes for fabric conditioning and processing, and food processing

We will describe the use of fungal enzymes in the dairy industry in Section 17.24, but there are many other aspects of both clothing and food manufacture that depend on enzymes produced by fungal cultures (see Fig. 17.27, above). The global industrial enzymes market is projected to reach a value of $6.30 billion by 2022; proteases accounted for the largest market share due to their wide range of applications in food and beverage, detergent, and biofuel industries. The food and beverages sector had the greatest value overall in 2016, with extensive requirements for carbohydrases in food processing, brewing, baking, and biofuel manufacturing (source: https://www.marketsandmarkets.com/PressReleases/industrial-enzymes.asp).

The textiles industry is also very large and lucrative, and even with the successful emergence of synthetic fibres such as nylon and polyester, a great many of our fabrics are still made from natural fibres like cotton (cellulose) fibres and wool and silk (protein) fibres which can be processed in various ways with natural enzymes (Vigneswaran et al., 2014).

The fabric processing with which we are individually most familiar is that resulting from the inclusion of fungal enzymes in detergents used for clothes washing. Enzymes included in biological detergents must be active under alkaline conditions: they include proteinases, lipases, amylases (used to remove protein, grease and sugar soiling) and cellulases (for colour brightening and fibre restoration). Some of these enzymes are derived from bacterial sources, but many are fungal enzymes.

Enzymes are also used during manufacture of textile products. Emerging areas of development include:

• Enzymatic preparation of natural fibres; biopreparation allows the removal of impurities prior to dyeing and saves water, natural fibres can also be modified to produce value-added products (for example the addition of silk peptides to wool), and surface modification of wool fibres to improve the feel of the final fabric. Hydrolytic enzymes including pectinases, cellulases, proteinases, and xylanases have been applied to cotton processing, resulting in fabrics with good absorbency that feel soft to the touch.
• Enzymatic bioprocessing of synthetic fibres, increasing functionality and adding value of polyester, polyamide or acrylic fibres.
• Remediation of textile effluents; bioremediation and effluent processing are important aspects of fabric processing, and enzymes can help here, too, for example laccases decolourise waste dyes.

Cellulase treatment of cotton fabrics is an environmentally friendly way of improving the property of the fabrics. Although cellulases were introduced into textile manufacture only in the 1990s, they are now one of the most frequently used group of enzymes for these applications. Cellulases have proved so popular because of their ability to modify cellulosic fibres in a controlled manner that improves the quality of the fabrics (Mojsov, 2014; Shahid et al., 2016).

When biofinishing cotton fabrics with cellulases, loose fibres are removed more efficiently and more gently than mechanical methods can achieve. An interesting application is in the preparation of ‘stone-washed' denim by a process known as biostoning. The textile industry is, of course, a fashion industry and for some years it has been fashionable for denim clothes to have a worn, faded, look and be soft to the touch. Traditionally, denim jeans manufacturers have washed their garments with pumice stones to achieve these desirable features, hence: stone-washed jeans.

The disadvantages of using stone for washing denim garments included damage to equipment by tumbling stones, difficulty of removing residual pumice from processed clothing, and particulate material clogging drainage channels. The still fashionable aged look is obtained by combining cellulase enzyme treatment with some form of mechanical distressing such as beating or friction. Using cellulase immobilised on a pumice carrier has advantages and can both reduce process costs and raise the activity of the enzyme (Pazarlioğlu et al., 2005; Soares et al., 2011; Vigneswaran et al., 2014).

Many of the treatment and finishing processes in the wool industry require chemicals that are environmentally unfriendly, particularly treatments aimed at reducing shrinkage of wool garments. Traditional treatments require strong acidic chlorine and results in polluting wastes. This generates interest in the use of enzymes to achieve the same effects on wool. A range of proteolytic enzymes are the candidates but they penetrate and degrade the internal wool structure during processing, causing unwelcome fibre damage. Natural enzymes can be modified or immobilised to control fibre degradation by enzymes, pointing the way to successful development of enzymatic treatments for achieving a variety of finishing effects for wool-containing products (Shen et al., 2007; Soares et al., 2011; Vigneswaran et al., 2014).

Enzymes are also used extensively in food biotechnology. Several examples feature elsewhere in this chapter. As an example here we note that the production of apple juice is the largest in the juice industry after grapes, and in order to maximise the yield of extracted juice, enzymes are incorporated into the procedure. This is common feature among a wide variety of sectors in the commercial food processing industry as they increase the output of product without additional capital investment.

Processing apples utilises macerating enzymes, pectinases, cellulases and hemicellulases (Table 11; Bhat, 2000), in two separate steps: extraction and clarification. The enzymes are used in the extraction to liquefy the fruit, increasing the yield of juice collected and enhancing release of other important cell ingredients such as antioxidants and vitamins. In the second step the enzymes are used to remove any precipitates that are formed from insoluble pectin.  Because the enzymes are mixed with the juice, the two need to be separated before packaging and distribution. This is usually achieved by adding gelatine as a fining agent which causes the enzymes to clump together in ‘flocs’ which can then be removed by filtration. One problem with this process is that the enzymes are used only once. Immobilisation of enzymes on polysaccharide gels, nylon filter membrane or particulate carriers enables them to be recycled (Sandri et al., 2011).

The microbial enzymes used for industrial processes are largely produced by liquid fermentation  but solid state fermentation has great potential for the production of enzymes (Pandey, 2003). For example, enzyme preparations from Phanerochaete chrysosporium, Aspergillus oryzae, Aspergillus giganteus and Trichoderma virens, produced by solid-state fermentation on cotton seed-coat waste (which serves as both substrate and enzyme inducer) produced enzymes that could be used effectively to degrade impurities in cotton fabrics during biopreparation (Csiszár et al., 2007; Vigneswaran et al., 2014).

The search continues for new enzymes from other organisms by screening microorganisms sampled from new environments or developed by modification of known enzymes using protein engineering or recombinant DNA technology (Olempska-Beer et al., 2006; Anbu et al., 2017).

Updated July, 2019