Figure 1. Consumption of raw materials for various human needs per person and year in Germany 1992. The water consumption is only for household use. These numbers are still valid. The energy consumption per capita has hardly changed since then. However, now (2010) 11% is derived from renewable resources (biomass, solar, water, wind) (AGEB, 2010). The arrowheads indicate the current increase in biotechnological processing of the products for different demands. For food and animal feed, only renewable raw materials (biomass) can be used; the figures to the right give the percentage for biomass of the raw materials currently used for the production. They can, especially for energy, only increase when they do not interfere with the biomass demand for food and feed. Due to the low material demands for hygiene, fine chemicals, and health products, 0–100% of the raw materials can be biomass, depending on the product. After the use of the products, the unavoidable waste must be recycled in a sustainable manner. Besides wastewater, this results in about 1000 kg of solid waste per year (soil, building materials, plastics, sludge, etc.). Energy is measured in coal equivalents.

Figure 2. Schematic view of an ideal sustainable biotechnological production process. Biomass as a regenerable resource is converted into desired products with minimal waste and by-product production. The waste and by-products must be completely recycled.

Figure 3. Process for dextrin production, with reaction vessel (a), filter (b), reservoir (c), and concentration unit (d).

Figure 4. The factory of the Rohm and Haas Company, Darmstadt, Germany, 1911.

Figure 5. (a) Market for enzymes used as biocatalysts for different purposes (2010), and (b) the increase in the application of enzymes reflected in the number of employees in the industry producing enzymes for biocatalytic purposes and their worldwide sales since 1970. Number of Novozymes employees that has about 50% of the world market for such enzymes (squares), and value of their worldwide sales (filled circles) (Novozymes yearly reports, last one from 2010). The value of the world production of technical enzymes is much larger than that shown in (a), as many companies that use enzymes as biocatalysts produce them in-house in order to have a safe and stable enzyme supply and/or protect their proprietary knowledge.

Figure 6. Classification of biocatalytic processes with enzymes as biocatalysts. I must be performed with enzymes in living cells, II can be performed with enzymes in living or dead cells, and III with isolated enzymes. For I now mainly designed cells are used, and for II high-yield cells for one-step reactions that do not require cosubstrate regeneration are used. Processes I–III will be covered in this book.

Figure 7. Comparison of the old (chemical) and the new (enzyme) process for the hydrolysis of penicillin G. The product, 6-aminopenicillanic acid (6-APA), is used for the synthesis of semisynthetic penicillins with side chains other than phenylacetic acid. In the enzyme process, the by-product phenylacetic acid can be recycled in the production of penicillin by fermentation(from Tischer, 1990).

Figure 8. The enzyme process for the hydrolysis of starch to glucose, and the isomerization of glucose to fructose (w/v = weight per volume) (see Chapters , , and ).

Figure 9. Time dependence (progress curves) of equilibrium- (solid line) and kinetically (broken line) controlled processes catalyzed by enzymes. The suitable end points of these processes are those where the maximum product concentration or property is achieved – that is, A for the kinetically and B for the equilibrium-controlled process. Such processes are illustrated with the hydrolysis of lactose in milk or whey. Whey is an inevitable by-product in cheese production, where mainly protein and fats are precipitated in the milk by addition of a “coagulating” enzyme (chymosin or rennin, a carboxyl acid peptidase, EC 3.4.23.4). The remaining liquid phase (whey) contains ~5% sugars (mainly lactose, a disaccharide galactosylglucose), 1% protein, 1% amino acids, and 1% ions (Ca ²⁺, Na ⁺, phosphate ions, etc.). Previously, with mainly small dairies, whey was used as a feed, or condensed to various sweet local products. Today, in large cheese-producing dairies, up to 10 ⁷ tons of whey is formed each year that cannot be used as before. The main content lactose cannot be used as a sweetener as a part of the population cannot tolerate lactose (this fraction is higher in parts of Asia and Africa). When it is hydrolyzed, its sweetness is increased. The enzyme β-glucosidase that catalyzes the hydrolysis of lactose also catalyzes the kinetically controlled synthesis of tri- and tetrasaccharides. When lactose is consumed, these oligosaccharides are hydrolyzed. This also illustrates the formation of undesired by-products in enzyme-catalyzed processes. The oligosaccharides are by-products in the equilibrium-controlled hydrolysis of lactose. On the other hand, in the kinetically controlled synthesis of the oligosaccharide that can be used as prebiotics, by-product formation is due to the hydrolysis to monosaccharides (Illanes, Wilson, and Raiman, 1999; Bruins et al., 2003). The formation of the by-products must be minimized by selecting suitable process conditions and biocatalysts.

Figure 10. Steps to be considered in the design of an enzyme process with isolated enzymes or an enzyme in dead cells (processes II and III in Figure 6) to produce existing or new products (bold numbers refer to chapters in this book). ^*Process window = the range in a pH–T- (or pH–[S]-, pH–[P]-, T–[S]-, T–[P]-) plane where the reaction can be carried out with a given yield or optical purity, and where the properties (activity, selectivity, stability) of the biocatalyst are optimal. For multienzyme processes with living cells (process I in Figure 6), the optimal process design requires metabolic engineering, and other boundary conditions than those above must be considered. With optimal metabolic engineering, almost quantitative conversion of the substrate(s) to the desired product can be obtained. Due to the many reactions involved, the time course of the reactions cannot be described as quantitatively as the processes above. The design of these processes will be covered in Chapter .