Yeasts nitrogen sources

Regulations specify a considerable Hst of additives and treatments which may be permitted under controlled limits and conditions. It is important to note that no wine receives mote than a few of these treatments, and many have none. For example, most grape musts ferment readily without additions, but some extra nitrogen source for the yeasts is occasionally beneficial. If some is requited, ammonium phosphate is the most commonly used. 

The yield was highest with starch or dextrin, intermediate and about the same with sucrose, glucose, maltose and lactose and poorest with glycerol. Kanamycin was produced by media containing soybean meal, peanut meal, cottonseed meal, corn steep liquor, peptone, yeast extract or meat extract, with or without sodium nitrate. Commercially available soybean meal was recognized to be one of the best nitrogen sources. The addition of corn steep liquor, peptone, yeast extract or nitrate to the soybean meal promoted the production of kanamycin. 

Nitrogen sources include proteins, such as casein, zein, lactalbumin protein hydrolyzates such proteoses, peptones, peptides, and commercially available materials, such as N-Z Amine which is understood to be a casein hydrolyzate also corn steep liquor, soybean meal, gluten, cottonseed meal, fish meal, meat extracts, stick liquor, liver cake, yeast extracts and distillers solubles amino acids, urea, ammonium and nitrate salts. Such inorganic elements as sodium, potassium, calcium and magnesium and chlorides, sulfates, phosphates and combinations of these anions and cations in the form of mineral salts may be advantageously used in the fermentation. 

Two bacterial Shewanella species, S. putrefaciens and S. oneidensis, previously selected on the basis of their ability to degrade azo dyes, were also tested in saline medium at different salt concentrations of up to 10% to evaluate their potential to decolorize four structurally different azo dyes Reactive Black 5, Direct Red 81, Acid Red 88, and Disperse Orange 3. Full decolorization was reached at salt concentrations up to 6% the decolorization velocity was inversely related to salt concentration. The rate of decolorization was increased by yeast extract and a calcium source, while was decreased by glucose and by a nitrogen source [54]. 

The ease of the Strecker synthesis from aldehydes makes a-aminonitriles an attractive and important route to a-amino acids. Fortunately, the microbial world offers a number of enzymes for carrying out the necessary conversions, some of them highly stereoselective. Nitrilases catalyze a direct conversion of nitrile into carboxylic acid (Equation (11)), whereas nitrile hydratases catalyze formation of the amide, which can then be hydrolyzed to the carboxylic acid in a second step (Equation (12)). In a recent survey, with a view to bioremediation and synthesis, Brady et al have surveyed the ability of a wide range of bacteria and yeasts to grow on diverse nitriles and amides as sole nitrogen source. This provides a rich source of information on enzymes for future application. 

Figure 2. Influence of yeast extract on the production of APPL by cultures of S. badius and S. viridosporus. The bacteria were grown in minimal culture media with Indulin (0.5%) as source of carbon and either yeast extract (0.6%) or NH4CI (0.02%) as nitrogen source. Q = APPL produced by S. badius grown in the presence of either NH4CI or yeast extract. (Reproduced with permission from Ref. 11, 1989 ASM.) o = APPL produced by S. viridosporus grown in the presence of either NH4CI or yeast extract.

As for the cultivation of other types of marine microorganisms, e.g., those with a specific potential for the production of biologically active metabolites, predominantly small-scale experiments (shake flasks) have been described. Alternatively, artificial seawater or 25 50 75 90% natural seawater has served as a basis for nutrient media. The concentrations of carbon and nitrogen sources reached up to 2 % (w/w) starch, glucose, molasses, glycerol, soybean oil, yeast extract, malt extract, beef extract, peptone, cornsteep liquor and NZ-amine. In the absence of artificial or natural seawater, high concentrations of... 

Carbon source (glucose), nitrogen source, complex protein source (yeast exuact, serum. ..), small amounts of organics, antifoam... 

Preparation and sterilization of medium Typical medium consists of corn steep liquor (4 percent to 5 percent dry weight) an additional nitrogen source such as soy meal, yeast extract, whey a carbon source such as lactose and various buffers. 

The significance of yeast extract and KH2P04 for lactic acid formation indicates the important role of protein and inorganic phosphate in the metabolism of L. lactis. The lesser influence of polypeptone compared with yeast extract proves that yeast extract is a good nitrogen source for nisin and lactic acid production. The influences of pH and temperature were not significant in this screening experiment, because this test was carried out close to the optimal conditions of these two variables (16). 

Because yeast extract is very expensive, we studied the effect of CSL supplement in order to reduce the amount of yeast extract. CSL has been the focus of attention as an alternative nitrogen source (8,12). As shown in Fig. 7, the bacterial conversion was very poor when only CSL was used as a nitrogen source. Even if yeast extract had a significant effect on cell growth, when 5 g/L of yeast extract and 15 g/L of CSL were used as nitrogen sources, a bioconversion yield and productivity of 95% and 2.2 g/(L-h), respectively, could be obtained. 

Besides the use of amino acids as a nitrogen source, flor yeast may use these compounds to balance the oxidation-reduction potential under conditions of restricted oxygen availability. This can be achieved by releasing amino acids into the medium to restore the intracellular redox balance by oxidation of excess NADH (Mauricio et ah, 2001a,b Moreno-Arribas and Polo, 2005 Valero et ah, 2003). 

Efficient carbon and nitrogen sources for the production of DOD from triolein were glucose, galactose, fructose, and yeast extract, respectively. Under optimized conditions, the maximum yield of DOD production represented 66% of substrate. These results demonstrated that natural vegetable oils, without being intentionally hydrolyzed, could be used as efficient substrates for the microbial production of value-added hydroxy fatty acids by PR3. 

Haywood, G. W., and Large, P. J., 1981, Microbial oxidation of amines dish ibution, purification and properties of two primary amine oxidases from die yeast Candida boidinii grown on amines as sole nitrogen source, Biochem. J. 199 187n201. 

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