Chapter 7 fatty acids; certain central metabolites(such as TCA cycle intermediates) carbohydrates Carbohydrates are the most widely utilised carbon substrate by exopolysaccharide producing micro-organisms and are used as substrate for commercial production. The structure of the exopolysaccharide is generally independent of the carbon substrate However, choice of carbon substrate can influence both the quantity produced and the extent of acylation of exopolysaccharides. The bacteria that produce dextran are unusually specific in their carbon substrate requirement for exopolysaccharide production: they synthesise dextran only when grown on sucrose and are apparently unable to synthesise the polymer when grown on other substrates, such as glucose ∏ Why do you think carbohydrates are the most widely utilised carbon substrate for commercial production? Carbohydrates are relatively cheap, available in large quantities and utilisable source of carbon and energy for most micro-organisms. These cons are particularly important for those exopolysaccharides produced on a Utilisable nitrogen sources for exopolysaccharide producing organisms include ammonium salts; · amino acid · nitrate dinitrogen(nitrogen gas) Ammonium salts or amino acids are by far the most commonly used nitrogen sources in production media. Nitrate is rarely used. Although most nitrogen fixing micro-organisms do produce exopolysaccharide, their growth and the quantity of the polymer produced is often improved if a fixed source of nitrogen, such as Nh, is cations Most micro-organisms require various cations for optimal growth, in particular K and Ca. Other cations(trace elements) are required in smaller quantities and, in some culture media, may be present as components of other ingredients Phosphate is the major anionic requirement of micro-organisms K has a role in substrate uptake and during efficient exopolysaccharide synthesis, adequate supplies of this ion is essential for ensuring sufficient intracellular carbon substrate is maintained. Other ions, such as phosphate and magnesium, have roles in the acylation of exopolysaccharides and influence their physical properties.202 Chapter 7 0 hydrocarbons; fattyacids; certain central metabolites (such as TCA cycle intermediates). Carbohydrates are the mast widely utilised &n substrate by exopolysamharide producing micro-organisms and are used as substrate for commercial production. The structure of the exopolysaccharide is generally independent of the carbon substrate. However, choice of carbon substrate can influence both the quantity produced and the extent of acylation of exopolysaccharides. The bacteria that produce dextran are unusually specific in their carbon substrate requirement for exopolysaccharide production: they synthesise dextran only when grown on sucrose and are apparently unable to synthesise the polymer when grown on other substrates, such as glucose. Why do you think carbohydrates are the most widely utilised carbon substrate n for commercial production? cartmhydrates Carbohydrates are relatively cheap, available in large quantities and are readily utilisable source of carbon and energy for most miao-organisms. These considerations are particularly important for those exopolysaccharides produd on a large (bulk chemical) scale. nitrogen sources Utilisable nitrogen sources for exopolysaccharide producing organisms include: ammoniumsalts; 0 aminoacids; nitrate; dinitrogen (nitrogen gas). Ammonium salts or amino acids are by far the most commonly used nitrogen sources in production media. Nitrate is rarely used. Although most nitrogen fixing micmrganisms do produce exopolysaccharide, their growth and the quantity of the polymer produced is often improved if a fixed source of nitrogen, such as M, is supplied. Most micro-organisms require various cations for optimal growth, in particular K', Mg", Fe2+ and Ca2+. Other cations (trace elements) are required in smaller quantities and, in some culture media, may be present as components of other inments. Phosphate is the major anionic requirement of micro-organisms. K+ has a role in substrate uptake and during efficient exopolysaccharide synthesis, adequate supplies of this ion is essential for ensuring sufficient intracellular carbon substrate is maintained. Other ions, such as phosphate and magnesium, have roles in the acylation of exopolysaccharides and influence their physical properties. cations