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PubMed2005

Impact of land use practices on faunal abundance, nutrient dynamics and biochemical properties of desert pedoecosystem.

Increased dependence of resource-poor rural communities on soils of low inherent fertility are the major problem of desert agroecosystem. Agrisilviculture practices may help to conserve the soil biota for maintaining essential soil properties and processes in harsh climate. Therefore, the impacts of different land use systems on faunal density, nutrient dynamics and biochemical properties of soil were studied in agrisilviculture system of Indian desert. The selected fields had trees (Zizyphus mauritiana, Prosopis cineraria, Acacia nilotica) and crops (Cuminum cyminum, Brassica nigra, Triticum aestivum) in different combinations. Populations of Acari, Myriapoda, Coleoptera, Collembola, other soil arthropods and total soil fauna showed significant changes with respect to different land use practices and tree species, indicating a strong relation between above and below ground biodiversity. The Coleoptera exhibited greatest association with all agrisilviculture fields. The Z. mauritiana system indicated highest facilitative effects (RTE value) on all groups of soil fauna. Soil temperature, moisture, organic carbon, nitrate- and ammonical-nitrogen, available phosphorus, soil respiration and dehydrogenase activity were greater under tree than that of tree plus cropping system. It showed accumulation of nitrate-nitrogen in tree field and more utilization by crops in cultivated lands. Positive and significant correlation among organic carbon, nitrate- and ammonical-nitrogen, phosphorus, soil respiration and dehydrogenase activity clearly reflects increase in soil nutrients with the increase in microbial and other biotic activity. P. cineraria field was the best pedoecosystem, while C. cyminum was the best winter crop for cultivation in desert agroforestry system for soil biological health and soil sustainability. The increase in organic carbon, soil nutrients and microbial activity is associated with the increase in soil faunal population which reflect role of soil fauna in fertility building. This suggests that strategies may be developed for nurturing fertility-building soil fauna and managing degraded pedoecosystem in desert just by adopting suitable agricultural practices.

Agriculture↗

PubMed2026

Microbial aerobic degradation of 4-isopropylnitrobenzene by Sphingobium yanoikuyae strain SG1.

4-Isopropylnitrobenzene (4-IPNB) is a nitroaromatic compound commonly employed as an intermediate in pesticide synthesis and chemical manufacturing. Despite its potential environmental persistence and ecological risks, the microbial degradation pathway of 4-IPNB remains largely unknown. In this study, a Gram-negative bacterium, designated Sphingobium yanoikuyae strain SG1, was isolated from a pesticide manufacturing site in Brazil for its ability to utilize 4-IPNB as the sole added source of carbon, nitrogen, and energy. Aerobic degradation of 4-IPNB by strain SG1 was accompanied by nitrite release, and intermediate-trapping experiments revealed the transient accumulation of 4-isopropylcatechol (4-IPC). Together, these findings support the initial conversion of 4-IPNB to 4-IPC through oxidative denitration and dihydroxylation. Genomic and transcriptomic analyses further inferred several candidate nitroarene dioxygenases that may catalyze this initial reaction. Furthermore, the downstream metabolism of 4-IPC proceeded via both meta- and ortho-cleavage pathways, with cell-extract enzyme assays demonstrating predominant meta-cleavage activity under the tested conditions. Strain SG1 also degraded 4-IPNB in nonsterile soil slurry microcosms, extending its degradation capability beyond defined liquid culture. This study provides the first comprehensive insight into the microbial aerobic degradation of 4-IPNB, advances our understanding of the environmental fate of emerging nitroaromatic contaminants, and supports the potential of strain SG1 in 4-IPNB biodegradation and removal.

Sphingomonadaceae↗

PubMed2003

Optimization of soil physical and chemical conditions for the bioremediation of creosote-contaminated soil.

Mispah type soil (FAO : Lithosol) contaminated with > 250 000 mg kg(-1) creosote was collected from the yard of a creosote treatment plant. The soil's carbon, nitrogen and phosphorus contents were determined. Due to creosote contamination, the carbon content of the soil was found to be 130,000 mg C kg(-1). This concentration was found to greatly affect the nitrogen content (0.08%). The phosphorus content was less affected (4.5%). It was estimated that a nutrient amendment to bring the soil to a C : N 10 : 1 would be adequate to stimulate microbial growth and creosote degradation. The soil was amended with a range of C : N ratios below and above the estimated ratio. In one of the treatments, the phosphorus content was amended. Sterile and natural controls were also set up. The soil was incubated at 30 +/- 2 degrees C on a rotary shaker at 150 rpm in the dark for six weeks. Water content was maintained at 70% field capacity. The lowest nitrogen supplementation (C : N = 25 : 1) was more effective in enhancing microbial growth (3.12E + 05) and creosote removal (68.7%) from the soil. Additional phosphorus was not very effective in enhancing the growth of microorganisms and removal of creosote. The highest nitrogen supplementation (C : N = 5 : 1) did not enhance microbial growth and creosote removal. Phenolics and lower molecular mass polycyclic aromatic hydrocarbons (PAHs) were observed to be more susceptible to microbial degradation than higher molecular mass compounds. Nutrient concentration, moisture content and pH were thus observed to play very significant roles in the utilization of creosote in soil. These results are being used for the development of a bioremediation technology for the remediation of creosote contaminated soils in a treatment plant in South Africa.

Bacteria↗

PubMed1986

[The influence of cellulose and various starches in feed on nitrogen metabolism in growing swine].

In N-balance experiments with a total of 49 female fattening pigs with a live weight between 33 and 47 kg the influence of cellulose supplements (exchanger principle) and changing quotas of maize starch and maize soak starch in semisynthetic feed mixtures on parameters of N-utilization was studied. The results show that there may be a positive influence of the supplement of cellulose on total N utilization (b-value, Gebhardt, 1963). One can conclude that, apart from a shift of the ways of N-excretion through faeces and urine, the utilization of products of microbial protein synthesis for N-retention is possible to a nutrition-physiologically relevant degree. The influence of the kind of starch on N-utilization was small.

Animal Feed↗

PubMed1998

Biodegradation of atrazine under denitrifying conditions.

Anaerobic biodegradation of atrazine by the bacterial isolate M91-3 was characterized with respect to mineralization, metabolite formation, and denitrification. The ability of the isolate to enhance atrazine biodegradation in anaerobic sediment slurries was also investigated. The organism utilized atrazine as its sole source of carbon and nitrogen under anoxic conditions in fixed-film (glass beads) batch column systems. Results of HPLC and TLC radiochromatography suggest that anaerobic biotransformation of atrazine by microbial isolate M91-3 involved hydroxyatrazine formation. Ring cleavage was demonstrated by 14CO2 evolution. Denitrification was confirmed by detection of 15N2 in headspace samples of K15NO3-amended anaerobic liquid cultures. In aquatic sediments, mineralization of uniformly ring-labeled [14C]atrazine occurred in both M91-3-inoculated and uninoculated sediment. Inoculation of sediments with M91-3 did not significantly enhance anaerobic mineralization of atrazine as compared to uninoculated sediment, which suggests the presence of indigenous organisms capable of anaerobic atrazine biodegradation. Results of this study suggest that the use of M91-3 in a fixed-film bioreactor may have applications in the anaerobic removal of atrazine and nitrate from aqueous media.

Atrazine↗

PubMed2003

Biotransformation of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) by denitrifying Pseudomonas sp. strain FA1.

The microbial and enzymatic degradation of a new energetic compound, 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20), is not well understood. Fundamental knowledge about the mechanism of microbial degradation of CL-20 is essential to allow the prediction of its fate in the environment. In the present study, a CL-20-degrading denitrifying strain capable of utilizing CL-20 as the sole nitrogen source, Pseudomonas sp. strain FA1, was isolated from a garden soil. Studies with intact cells showed that aerobic conditions were required for bacterial growth and that anaerobic conditions enhanced CL-20 biotransformation. An enzyme(s) involved in the initial biotransformation of CL-20 was shown to be membrane associated and NADH dependent, and its expression was up-regulated about 2.2-fold in CL-20-induced cells. The rates of CL-20 biotransformation by the resting cells and the membrane-enzyme preparation were 3.2 +/- 0.1 nmol h(-1) mg of cell biomass(-1) and 11.5 +/- 0.4 nmol h(-1) mg of protein(-1), respectively, under anaerobic conditions. In the membrane-enzyme-catalyzed reactions, 2.3 nitrite ions (NO(2)(-)), 1.5 molecules of nitrous oxide (N(2)O), and 1.7 molecules of formic acid (HCOOH) were produced per reacted CL-20 molecule. The membrane-enzyme preparation reduced nitrite to nitrous oxide under anaerobic conditions. A comparative study of native enzymes, deflavoenzymes, and a reconstituted enzyme(s) and their subsequent inhibition by diphenyliodonium revealed that biotransformation of CL-20 is catalyzed by a membrane-associated flavoenzyme. The latter catalyzed an oxygen-sensitive one-electron transfer reaction that caused initial N denitration of CL-20.

Biotransformation↗

PubMed2001

Screening and characterization of fructosyl-valine-utilizing marine microorganisms.

We describe the isolation of microorganisms utilizing fructosyl-amine (Amadori compound) from the marine environment and of fructosyl-amine oxidase from a marine yeast. Using fructosyl-valine (Fru-Val), a model Amadori compound for glycated hemoglobin, we isolated 12 microbial strains that grow aerobically in a minimal medium supplemented with Fru-Val as the sole nitrogen source. Among these strains, a yeast strain identified as Pichia sp. N1-1, produced a Fru-Val-oxidizing enzyme. The enzyme was purified in its active form, a single-polypeptide water-soluble protein of 54 kDa by gel electrophoresis, producing H(2)O(2) with the oxidation of Fru-Val. By its substrate specificity, the enzyme was categorized as a novel fructosyl-amine oxidase. This is the first study on the isolation of microorganisms utilizing fructosyl-amine in the marine environment and of fructosyl-amine oxidase from budding yeast.

Journal Article↗

PubMed1993

Microbial metabolism of quinoline and related compounds. XVIII. Purification and some properties of the molybdenum- and iron-containing quinaldic acid 4-oxidoreductase from Serratia marcescens 2CC-1.

Serratia marcecens 2CC-1 utilizes quinaldic acid (quinoline 2-carboxylic acid) as sole source of carbon, nitrogen and energy. Growth of strain 2CC-1 on quinaldic acid as well as on nicotinic acid and hypoxanthine was inhibited completely by the molybdate antagonist tungstate, whereas growth on kynurenic acid and 6-hydroxynicotinic acid was not affected by tungstate. The synthesis of the molybdenum-containing hydroxylases quinaldic acid 4-oxidoreductase and nicotinic acid 6-oxidoreductase was found to be inducible. In addition, Serratia marcescens 2CC-1 produced a constitutively expressed xanthine oxidoreductase. Quinaldic acid 4-oxidoreductase was purified 1075-fold with a recovery of 5%. For catalytic activity, artificial electron acceptors were necessary. The 95-100-kDa enzyme was a heterodimer with subunit molecular masses of 75-80 kDa and 18-19 kDa. Quinaldic acid 4-oxidoreductase contained 2.3-3.7 g atom of iron and 0.5-0.6 g atom of molybdenum per mol of enzyme. The absorption spectrum exhibited maxima at 280 nm, 334 nm, 480 nm and a shoulder at 550 nm, with A280/A334 = 4.8, A280/A450 = 10.0, A280/A480 = 9.4, and A450/A550 = 1.6, suggesting the absence of a flavin cofactor. Acridine, quinacrine, ethylenediaminetetraacetate, 2,2'-dipyridyl, 1,10-phenanthroline and iodoacetate did not affect enzyme activity. p-Hydroxymercuribenzoate, m-arsenite, cyanide and methanol were effective inhibitors of quinaldic acid 4-oxidoreductase. Cyanide-inhibited enzyme was reactivated by treatment with S2-, indicating the presence of a pterin molybdenum cofactor with a monooxo-monosulfidotype molybdenum center. Quinaldic acid 4-oxidoreductase showed a very high substrate specificity, quinaldic acid being the only substrate found to be transformed significantly.

Amino Acid Sequence↗

PubMed1996

Microbial amino acid synthesis and utilization in rats: the role of coprophagy.

Four rats were housed in cages with mesh floors; another four rats were housed in tubular anticoprophagy cages, in which they could not turn round to reach their own faeces. Both groups were fed for 6 d on a low-protein diet containing fermentable carbohydrates and 15NH4Cl. At the end of the experiment the rats were killed and their carcasses were homogenized, lysine was isolated by ion-exchange chromatography and its 15N enrichment measured by isotope-ratio mass spectrometry. The 15N enrichment in the lysine of the microbial fraction of faeces and the total amount of lysine in the body were also determined in order to estimate the amount of microbial lysine absorbed. The 15N enrichment in body lysine of non-coprophagic rats was not different from that previously measured in rats given unlabelled NH4Cl, but in coprophagic rats it was significantly higher. The daily absorption of microbial lysine by the coprophagic rats accounted for 20.7 (SE 2.55) mg/kg body weight0-75, but was only 0.5 (SE 1.04) mg/kg body weight0-75 for the non-coprophagic rats. This value was not significantly different from zero. The utilization of microbial amino acids via coprophagy resulted in a higher weight gain (adjusted for intake) in the coprophagic group (15.5 g/6 d) than in the non-coprophagic rats (3.1 g/6 d). It was concluded that, in rats, the utilization of microbial lysine occurred exclusively via coprophagy.

Amino Acids↗

PubMed1978

Production of gentamicins by Micromonospora purpurea.

The natural medium contained the following ingredients (g/l): glucose 8.0, or black strap molasses (treated with 0.2--0.3 g/l EDTA) 12.0, fodder yeast (50.0% total nitrogen) 2.0, or folder yeast (40.0% total nitrogen) 6.0, or yeast extract 8.0, or tryptone 8.0, and CaCO3 1.0. Treated black strap molasses with EDTA and fodder yeast proved to be effective in the fermentative production of gentamicins. The most suitable chelating agent was EDTA in the form of disodium for the treatment of Komombo molasses in a concentration of 0.2--0.3 g/l, while potassium ferrocyanide and methylene blue had depressing effects on the production of gentamicins. The most effective carbon source, present in Egyptian black strap molasses, was glucose. Addition of glucose to the medium was preferable at the beginning of the fermentation process. Trace elements present in molasses were very essential for the microbial growth and biosynthesis of gentamicins as proved when molasses ash was added to the natural medium. Organic nitrogen sources were more suitable than inorganic nitrogen sources for the production of gentamicins by Micromonospora purpurea. The microorganism utilized the synthetic medium, but the antibiotic yields were less than those produced in the natural medium. The synthetic medium exhibited stimulatory effects of certain amino acids, organic acids, vitamins, and purine and pyrimidine bases on the fermentative production of gentamicins. Therefore, the ingredients increasing yields of gentamicins were mainly phenylalanine, iso-leucine, lysine, methionine, leucine, arginine, glycine, beta-alanine, cystine, tryptophan, malic acid, maleic acid, cobalamin, folic acid, riboflavin, vitamin B1, vitamin B6, biotin, nicotinamide, uracil, adenine, guanine, and adenosine. Trace elements (Co, Mo, Fe, Cu, Zn, and Mn) exhibited their important role on the biosynthesis and production of gentamicins by Micromonospora purpurea.

Carbon↗

PubMed1994

Digestibility, nitrogen utilization, and voluntary intake of ensiled crab waste-wheat straw mixtures fed to sheep.

Crab waste and wheat (Triticum aestivum L.) straw mixtures, ensiled with different additives, were evaluated in metabolism and palatability trials. Crab waste and straw were mixed in proportions of 1:1, wet basis, with 20% water and different additives, and ensiled in 210-L metal drums double-lined with polyethylene bags. Thirty crossbred wethers (40 kg initial BW) were fed a 1) basal diet consisting of 75% orchardgrass (Dactylis glomerata L.) hay and 25% concentrate, 2) ensiled crab waste-wheat straw, with 16% (vol/wt) added glacial acetic acid, 3) crab waste-wheat straw ensiled with 20% dry molasses, 4) crab waste-wheat straw ensiled with 20% dry molasses and a microbial inoculant, and 5) ensiled wheat straw supplemented with urea. Apparent digestibility of DM and CP was lower (P < .05) for acetic acid-treated silages than for silages containing molasses. Nitrogen retention was higher (P < .05) for molasses-inoculant-treated silage than for the molasses-treated silage (5.4 vs 3.9 g/d). Ruminal NH3 N and blood urea N were higher (P < .05) for lambs fed the molasses-treated silages than for those receiving the acetic acid-treated crab waste mixture. Among the wethers fed crab waste silages, intake was lower (P < .01) for wethers receiving the acetic acid-treated silage than for those fed the molasses-treated mixtures. Treatment of crab waste-straw mixtures with molasses produced a palatable silage that was efficiently utilized by wethers.

Acetates↗

PubMed1977

General model of microbial growth and decomposition in aquatic ecosystems.

A model capable of simulating freely suspended and attached decomposers, particulate organic matter, labile and refractory dissolved organic matter, inorganic nitrogen, and phosphate in the open-water portion of lakes is presented. Examples are given showing the utility of the model when coupled to the whole-ecosystem model CLEANER.

Journal Article↗

PubMed2006

Bio-available amino acids and mineral nitrogen forms in soil of moderately mown and abandoned mountain meadows.

The abandonment of traditional mowing methods of mountain meadows in the Czech Republic at the end of the last century has resulted in secondary re-colonization of these areas. Altered accumulation of plant biomass resulted in a deceleration of N turnover. A mountain meadow may be regarded as a N-limited ecosystem in which plant nutrition is dependent on direct uptake of soil amino acids. The composition and distribution of ammonium ions, nitrate ions and the 16 bio-available proteinaceous amino acids were investigated in the top 7 cm of the Ah horizon of a Gleyic Luvisol in a long-term moderately mown meadow and an eleven year old, abandoned or uncut meadow. Ammonium N has a dominant role in both ecosystems. The moderately mown meadow showed accelerated N-turnover and higher net ammonization. The plant community showed a dependence on this form. Plant utilization of nitrates and amino acids appeared to be negligible. The uncut or abandoned meadow showed net ammonization from May (start of the experiment) through August, after which plant N-uptake consisted only of amino acids due to microbial immobilization. The release of bio-available nitrogen from spring until the beginning of summer in the Ah horizon was too low to explain total plant N-uptake. Glutamic acid, arginine and aspartic acids had the highest concentrations of any of the amino acids analyzed.

Agriculture↗

PubMed1994

Utilization of dissolved nitrogen by heterotrophic bacterioplankton: a comparison of three ecosystems.

The contributions of different organic and inorganic nitrogen and organic carbon sources to heterotrophic bacterioplankton in batch cultures of oceanic, estuarine, and eutrophic riverine environments were compared. The importance of the studied compounds was surprisingly similar among the three ecosystems. Dissolved combined amino acids (DCAA) were most significant, sustaining from 10 to 45% of the bacterial carbon demands and from 42 to 112% of the bacterial nitrogen demands. Dissolved free amino acids (DFAA) supplied 2 to 7% of the carbon and 6 to 24% of the nitrogen incorporated into the bacterial biomass, while dissolved DNA (D-DNA) sustained less than 5 and 12% of the carbon and nitrogen requirements, respectively. Ammonium was the second most important source of nitrogen, meeting from 13 to 45% of the bacterial demand in the oceanic and estuarine cultures and up to 270% of the demand in riverine cultures. Nitrate was taken up in the oceanic cultures (uptake equaled up to 46% of the nitrogen demand) but was released in the two others. Assimilation of DCAA, DFAA, and D-DNA combined supplied 43% of the carbon demand of the bacteria in the oceanic cultures, while approximately 25% of the carbon requirements were met by the three substrates at the two other sites. Assimilation of nitrogen from DCAA, DFAA, D-DNA, NH(4), and NO(3), on the other hand, exceeded production of particulate organic nitrogen in one culture at 27 h and in all cultures over the entire incubation period (50 h). These results suggest that the studied nutrient sources may fully support the nitrogen needs but only partially support the carbon needs of microbial communities of geographically different ecosystems. Furthermore, a comparison of the initial concentrations of the different substrates indicated that relative pool sizes of the substrates seemed to influence which substrates were primarily being utilized by the bacteria.

Journal Article↗

PubMed2026

Comparative profiling of microbial community structure, enzyme potential, metabolic features, and volatile composition in craft and Jiafan Huangjiu processes.

Craft Huangjiu and Jiafan Huangjiu represent two distinct industrial Huangjiu product outcomes with contrasting volatile profiles. This study compared craft Huangjiu (L70) and Jiafan Huangjiu (L79) to characterize their physicochemical, microbial, gene-level functional, metabolic, and volatile features. Because L70 involved mid-fermentation addition of finished Huangjiu, this comparison was not intended to isolate the sole effect of fermentation interruption versus continued fermentation. L79 showed more extensive carbon and nitrogen utilization, with lower residual substrates and higher ethanol and acetic acid contents than L70, whereas L70 retained a less complete fermentation state. At the volatile level, GC-MS and volatile metabolomics consistently showed an ester-enriched profile in L79 and a more alcohol-dominant profile in L70. FlavorDB-based putative annotation and threshold-based OAV analysis further indicated distinct database-assigned descriptor distributions and potential odor-active compounds, with more OAV > 1 ester-related compounds in L79. Metagenomic analysis showed that L70 was dominated by Lactobacillus acetotolerans, whereas L79 contained higher relative abundances of Saccharomyces cerevisiae, Aspergillus oryzae, Aspergillus flavus, and Fructilactobacillus fructivorans. Metagenomic functional annotation showed higher representation of hydrolysis-related CAZy genes and ester-related enzyme annotations in L79. KEGG-based pathway mapping further indicated greater gene-level potential for ethanol-, acetate-, and acetyl-CoA-related metabolism in L79. Accordingly, the L70 profile should be interpreted as the integrated final-product outcome of process intervention, exogenous input, and subsequent fermentation. The findings provide a comparative basis for future flavor regulation and process optimization in Huangjiu and other fermented alcoholic beverages.

Volatile Organic Compounds↗

PubMed1993

[The determination of a gross utilization of 15N-lysine in laboratory rats. 2. Comparative testing with an antibiotic supplement to the diet].

Wistar rats of a live weight of about 100 g received in 26 groups (4 animals/group) diets, each with a different lysine content. The rations given supplied the animals with 75%, 100% or 125% lysine of the calculated requirement. The source of protein in the diets was: barley (B), wheat (W), wheat gluten (WG), isolated soybean protein (assay protein) (S) or soybean meal (SM). For WG and S only the lysine levels 100% and 125% (SM = 116% and 125%) could be achieved. All diet groups were fed for 10 days with and without antibiotics (7 g Nebacitin/kg feed-DM). During the 7-day-period of the main experiment all 24 rations were supplemented with 0.5 g 15N-lysine/kg DM (48.3 atom-% 15N-excess, alpha-aminogroup 95% 15N-labelled). The nitrogen balance was improved only after feeding antibiotics with the diet S 100. It may be supposed that Nebacitin saved the second limiting amino acid methionine against microbial degradation in the digestion tract. The biological value (BV) of feed-proteins declined in the case of the diets B and W in the presence of antibiotics because the absorbed nitrogen was higher, this calculation basis for BV was therefore also higher without an improvement of the N-utilization. The 15N-excretion in faeces was significantly lower after feeding the diets B, W and WG with antibiotics. The 15N-excretion in urine was elevated in the most cases of the antibiotic supplement. The determination of a gross utilization of lysine and 15N-lysine resp. in relation to the lysine retention (availability) was not possible, neither using a labelling of diets with 15N-lysine.

Administration, Oral↗

PubMed1991

Evaluation of dairy food processing wash water solids as a protein source: III. Nitrogen utilization by heifers fed medium-concentrate diets.

Eight multicannulated heifers (average BW 415 +/- 34 kg) were used in a replicated 4 x 4 Latin square to evaluate fluid milk processing wash water solids (WWS) as a dietary N source. Heifers were fed corn/cottonseed hull-based diets containing soybean meal (control, 0% WWS N) or WWS replacing soybean meal at 33, 67, or 100% of supplemental dietary N. Total tract and ruminal DM and OM digestibilities decreased linearly or cubically (P less than .05) as dietary WWS N increased. Total ruminal VFA concentration (P less than .05) and propionic acid molar proportion (P less than .10) were greater in heifers fed 0 vs 100% WWS N. Heifers fed 0% WWS N had the greatest (P less than .05) ruminal ammonia concentration at all sampling times. Dietary WWS did not affect (P greater than .10) ruminal pH, fluid dilution rate, fluid flow, fluid volume, or turnover time. Total tract N digestibility decreased quadratically (P less than .10) with increasing WWS N in the diet. Supplemental WWS N did not affect (P greater than .10) flow of duodenal ammonia N or bacterial N, or efficiency of microbial N synthesis. Diets containing WWS N resulted in a cubic increase (P less than .10) in duodenal flow of essential amino acids compared with 0% WWS N; however, there were no differences in small intestinal amino acid disappearance. Data indicate that WWS can replace 33% of the soybean meal N in a corn/cottonseed hull-based diet without decreasing ruminal fermentation, fluid digesta kinetics, microbial efficiency, or small intestinal amino acid utilization.

Amino Acids↗

PubMed1972

Inorganic nitrogen assimilation in yeasts: alteration in enzyme activities associated with changes in cultural conditions and growth phase.

Ammonia assimilation has been investigated in four strains of Saccharomyces cerevisiae by measuring, at intervals throughout the growth cycle, the activities of several enzymes concerned with inorganic ammonia assimilation. Enzyme activities in extracts of cells were compared after growth in complete and defined media. The effect of shift from growth in a complete to growth in a defined medium (and the reverse) was also determined. The absence of aspartase (EC 4.3.1.1, l-aspartate-ammonia lyase) activity, the low specific activities of alanine dehydrogenase, glutamine synthetase [EC 6.3.1.2, l-glutamate-ammonia ligase (ADP)], and the marked increase in activity of the nicotinamide adenine dinucleotide phosphate-linked glutamate dehydrogenase (NADP-GDH) [EC 1.4.1.4, l-glutamate:NADP-oxidoreductase (deaminating)] during the early stages of growth support the conclusion that yeasts assimilate ammonia primarily via glutamate. The NADP-GDH showed a rapid increase in activity just before the initiation of exponential growth, reached a maximum at the mid-exponential stage, and then gradually declined in activity in the stationary phase. The NADP-GDH reached a higher level of activity when the yeasts were grown on the defined medium as compared with complete medium. The nicotinamide adenine dinucleotide-linked glutamate dehydrogenase (NAD-GDH) [EC 1.4.1.2, l-glutamate:NAD-oxidoreductase (deaminating)] showed only slight increases in activity during the exponential phase of growth. There was an inverse relationship in that the NADP-GDH increased in activity as the NAD-GDH decreased. The NAD-GDH activity was higher after growth on the complete medium. The glutamate-oxaloacetate transaminase (EC 2.6.1.1. l-aspartate:2-oxoglutarate aminotransferase) activity rose and fell in parallel with the NADP-GDH, although its specific activity was somewhat lower. Although other ammonia-assimilatory enzymes were demonstrable, it seems unlikely that their combined activities could account for the remainder of the ammonia-assimilatory capacity not accounted for by the NADP-GDH. The ability of aspartate to serve as effectively as glutamate as the sole source of nitrogen for the growth of yeast apparently resides in their ability to utilize aspartate for amino acid biosynthesis via transamination.

Alanine↗