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Free amino nitrogen effect

The initial concentration of ammonium cations and amino acids in the must is one of the most important elements in determining the need for supplements. When the NH4+ concentration is less than 25 mg/1, nifiogen addition is necessary. It is useful for concenfiations to be between 25 and 50 mg/1. Above this concentration, supplementing has no adverse effects. It is, however, unlikely that an addition will activate the fermentation. If the values are expressed in free amino nitrogen (FAN), detectable by ninhydrin, between 70 and 140 mg/1 are necessary to have a complete fermentation of musts containing between 160 and 250 g of sugar per liter (Henschke and Jiranek, 1992). [Pg.86]

More data are needed on the effects of organic practices on phytochemicals and their precursors. How does modification of precursor pools affect biosynthesis For example, see studies on the effects of lower levels of free amino acids caused by a reduction in nitrogen input. [Pg.322]

Although these experiments showed growth was possible using casein hydrolysate, Rose also demonstrated that when the amino acid mixture was used rather than the intact protein, additional calories had to be provided as fat plus carbohydrate, if nitrogen balance was to be maintained. It was later shown that the carbohydrate was needed to protect the free amino acids from oxidation in the intestinal epithelium in the course of absorption. Further, amino acids are poorly tolerated by mouth, causing vomiting and/or diarrhea. After World War II attempts to feed very emaciated prisoners in concentration camps with protein hydrolysates were unsuccessful. It was then recognized that osmotic effects from the amino acids were responsible for the unpleasant consequences. [Pg.25]

The Klotz group has also found rate enhancements of decarboxylation reactions with PEI derivatives. Catalysis of decarboxylation of j -keto acids by small amines goes via a Schiff base intermediate. Mine s group has shown that unmodified PEI catalyzes dedeuteration effectively and that the reactions involve Schiff base intermediates 34, and references therein). Dodecyl-PEI containing free amino groups and quaternized nitrogens, dodecyl-PEI-Q-NHj, was found to be an effective catalyst for the decomposition of oxaloacetate (reaction 12) (92). At pH 4.5 the polymer is 10 times as effective as ethylamine. was found to be 3.5 x 10 " M at pH 4.5. [Pg.219]

Middleboe, M., N. H. Borch, and D. L. Kirchman. 1995b. Bacterial utilization of dissolved free amino acids, dissolved combined amino acids and ammonium in the Delaware Bay estuary Effects of carbon and nitrogen limitation. Marine Ecology Progress Series 128 109-120. [Pg.117]

Flynn, K. J., and Al-Amoudi, O. A. (1988). Effects of nitrogen deprivation and darkness on composition of free amino acid pools in and on amino acid release from the diatom Phaeodactylum tricornutum Bohlin.J. Exp. Mar. Biol. Ecol. 119, 131—143. [Pg.367]


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