林可霉素生物合成培养基的优化

以花生粉和棉籽蛋白粉取代了原培养基中的黄豆饼粉,采用响应面法对林可霉素产生菌的发酵培养基进行了优化.首先通过单因素试验及正交实验确定替代氮源及其浓度,采用Plackett-Burman实验分析各因素的主效应,选出对响应值影响较大的3个因素,即花生粉、K2HPO4和玉米浆.对这些因素做爬坡实验,确定三个重要因素的中心点浓...     

Determination of energy and amino acid digestibility in growing pigs fed corn distillers' dried grains with solubles containing different lipid levels

Two experiments were conducted to estimate the digestibility of energy, nitrogen and amino acids (AA) in growing pigs fed diets containing one of five corn distillers' dried grains with solubles (DDGS), including three normal oil DDGS (NO-DDGS) and two low oil DDGS (LO-DDGS) samples. Exp. 1 was conducted to determine the digestible energy (DE) and metabolisable energy (ME) content. Six growing barrows (initial body weight [BW]: 35.1 +/- 2.2 kg) were allotted to a 6 x 6 Latin square design, with six periods and six diets. One diet was a corn soybean meal basal diet and the other five diets were based on corn, soybean meal and 28.8% DDGS. The average DE and ME values for the three NO-DDGS samples were 16.0 and 14.9 MJ/kg dry matter (DM). These values were 9 and 13% greater than the LO-DDGS values of 14.7 and 13.2 MJ/kg DM respectively. Exp. 2 was conducted to determine and compare apparent (AID) and standardised (SID) ileal digestibility for crude protein and AA in the five DDGS samples. Six growing barrows (initial BW, 32.2 +/- 1.9 kg) fitted with a simple T-cannula were allotted to a 6 x 6 Latin square design with six periods and six diets. Five of the diets were based on the five DDGS samples, and the remaining one diet was nitrogen-free diet based on cornstarch and sucrose. Titanium dioxide (0.1%) was used as inert marker. The results of the experiment showed the largest variation among the different samples in AID and SID for lysine (from 41.8 to 65.8% and 53.8 to 73.9% respectively) and threonine (from 54.3 to 73.8% and 65.2 to 79.5% respectively). Also, among the indispensable AA, the SID values for arginine, histidine, threonine and tryptophan observed in LO-DDGS were not different from the values derived from NO-DDGS. In conclusion, LO-DDGS may have decreased energy compared with NO-DDGS because of its lower fat content. However, oil removal during the production of DDGS may not affect amino acid digestibility.     

Fate of Fumonisin B1 in Naturally Contaminated Corn during Ethanol Fermentation

Two lots of corn naturally contaminated with fumonisin B₁ (15 and 36 ppm) and a control lot (no fumonisin B₁ detected) were used as substrates for ethanol production in replicate 8.5-liter yeast fermentations. Ethanol yields were 8.8% for both the control and low-fumonisin corn, while the high-fumonisin corn contained less starch and produced 7.2% ethanol. Little degradation of fumonisin occurred during fermentation, and most was recovered in the distillers' grains, thin stillage, and distillers' solubles fractions. No toxin was detected in the distilled alcohol or centrifuge solids. Ethanol fermentation of fumonisin-contaminated corn coupled with effective detoxification of distillers' grains and aqueous stillage is suggested as a practical process strategy for salvaging contaminated corn.     

Phytase production byAspergillus ficuum on semisolid substrate

Summary Phytase production byAspergillus ficuum was studied using solid state cultivation on several cereal grains and legume seeds. The microbial phytase was used to hydrolyze the phytate in soybean meal and cotton seed meal. Wheat bran, soybean meal, cottonseed meal and corn meal supported good fungal growth and yielded a high level of phytase when an adequate amount of moisture was present. The level of phytase production on solid substrate was higher than that obtained by submerged liquid fermentation. Higher levels of phosphorus (more than 10 mg Pi/100 g substrate) in the growth medium (static culture) inhibited phytase synthesis, and the degree of phosphorus inhibition was less apparent in semisolid medium than in liquid medium. A static cultivation on semisolid substrate produced a higher level of phytase (2-20-fold) than that obtained by agitated cultivation. The minimal amount of water required for growth and enzyme production on those substrates was about 15%, while the optimum level for phytase production was between 25 and 35% and that for cell growth was above 50%. Optimum pH for phytase production was between 4 and 6.A ficuum grew well on raw (unheated) substrate containing a minimal amount of water and produced as much phytase as on heated substrate. About half of the phytic acid in soybean meal and cottonseed meal was hydrolyzed by treatment withA. ficuum phytase.     

Production of a New Type of Acid Carboxypeptidase of Molds of the Aspergillus niger Group

The ability of 88 fungi, which had been obtained as high-potency strains for acid proteinase production, to produce a new type of acid carboxypeptidase (having on optimal pH of about 3 for hydrolysis of benzyloxycarbonyl-glutamyltyrosine) in surface koji culture was determined. Among the aspergilli, substantial amounts of this new acid carboxypeptidase were produced by Aspergillus saitoi, A. usamii, A. awamori, A. inuii, and A. niger. Maximum yields of acid carboxypeptidase per gram of substrate were obtained by submerged culture in a medium containing 0.9% defatted soybean and 0.6% wheat bran. However, the maximum enzyme concentration per milliliter was obtained with a medium containing 3% defatted soybean and 2% wheat bran. The terminal pH could be controlled by varying the concentrations of soybean oil meal and wheat bran. The maximum enzyme production was reached after 4 days or more at 30 C.     

Degradation of Uredospores of the Soybean Rust Fungus (Phakopsora pachyrhizi Syd.) by Cell-Free Culture Filtrates of the Mycoparasite Verticillium Psalliotae Treschow

Verticillium psalliotae isolates Taiw and Thai C are effective parasites of the soybean rust fungus. Cell-free culture filtrates of these fungi, prepared after growth on autoclaved uredospores, contained β-1,3-glucanase, chitinase and protease activities and caused degradations, when rust spores were treated with them for 24 or 72 h. During these lytic processes carbohydrates, amino compounds and N-acetylhexosamine were released. The carbohydrate fraction was composed of mannitol, arabitol, trehalose, glucose and unidentified substances showing low R_f-values during thin layer chromatography. The amino compounds consisted of 10 amino acids (leucine and/or isoleucine, phenylalanine, glutamic acid, valine, arginine, asparagine, glutamine, serine, aspartic acid, histidine) and 5—7 substances which could not be identified. Verticillium lecanii isolate Konz is a weak parasite of soybean rust. During growth on uredospores the fungus produced culture filtrates without chitinase activity and with low total activities of β-1,3-glucanase and protease. Compared with V. psalliotae, culture filtrates of V. lecanii exerted lower lytic activities on soybean rust uredospores. The results are consistent with the aspect that the rapid growth of V. psalliotae on soybean rust fungus is primarily based on the secretion of lytic enzymes which make nutrients available to the mycoparasite.     

Leaf protein concentrates: a comparison of protein production per acre of forage with that from seed and animal crops

The essential amino acid production for ten crops harvested for forage and fifteen crops harvested for seed was calculated from average crop yields in the United States for the ten-year period of 1953 to 1962. Highest yields per acre of essential amino acids were calculated from forages which could be processed into leaf protein concentrates. Alfalfa produced the highest yield per acre of essential amino acids of the twenty major crops; soybean seed was second. The calculated yields of edible protein and essential amino acids of leaf protein from corn were equal to or greater than the protein from the corn seed and several times that from animals fed the corn grain. At the present time, leaf protein concentrate may not be able to compete in cost with the by-product protein concentrates such as soybean meal, cottonseed meal, peanut meal, linseed meal, or tankage for feeding farm animals. However, further study of the production of leaf protein concentrates should be made to assure protein supplies for those regions where other adequate protein sources are lacking.     

Proteinase production by a species of Cephalosporium

An unidentified Cephalosporium species produced an extracellular proteinase when grown in a variety of fermentation media under submerged culture conditions. Maximal enzyme yields were obtained in a medium containing 2% corn meal, 1% soybean meal, and 0.5% CaCO₃ in tap water. Optimal proteinase production in this medium occurred within a 72- to 96-hr growth period. High enzyme yields were also attained with media in which cottonseed meal, Fermatein, Pharmamedia, or soybean-α-protein was substituted for the soybean meal. The substitution of these ingredients for the corn meal resulted in significantly decreased proteinase yields. The addition of minerals or vitamins to the corn meal-soybean meal fermentation medium failed to enhance proteinase production. The enzyme was most active in an alkaline environment; maximal caseinolysis occurred at pH 7.5, whereas pH 8.5 was optimal for either hemoglobin or β-lactoglobulin hydrolysis. Enzymatic activity was also noted with either bovine albumin fraction V or soybean-α-protein substrates, whereas ovalbumin was not susceptible to enzymatic attack. The enzyme was stable within the pH range of 3.0 to 9.5 at 25 C for 2 hr, and at 5 C for 24 hr. The proteinase was stable upon heating for 10 min at 35 to 45 C, but it was totally inactivated at 70 C. The proteinase was unaffected by soybean inhibitor, partially inactivated by lima bean inhibitor, and completely inactivated by ovomucoid inhibitor.     

Plant products affect growth and digestive efficiency of cultured Florida pompano (Trachinotus carolinus) fed compounded diets

Costs of compounded diets containing fish meal as a primary protein source can be expected to rise as fish meal prices increase in response to static supply and growing demand. Alternatives to fish meal are needed to reduce production costs in many aquaculture enterprises. Some plant proteins are potential replacements for fish meal because of their amino acid composition, lower cost and wide availability. In this study, we measured utilization of soybean meal (SBM) and soy protein concentrate (SPC) by Florida pompano fed compounded diets, to determine the efficacy of these products as fish meal replacements. We also calculated apparent digestibility coefficients (ADCs) for canola meal (CM), corn gluten meal (CGM), and distillers dried grains with solubles (DDGS), following typical methods for digestibility trials. Juvenile Florida pompano were fed fish-meal-free diets containing graded levels of SBM and SPC, and weight gain was compared to a control diet that contained SBM, SPC, and fish meal. Fish fed diets that contained 25-30 percent SBM in combination with 43-39 percent SPC had weight gain equivalent to fish fed the control diet with fish meal, while weight gain of fish fed other soy combinations was significantly less than that of the control group. Apparent crude protein digestibility of CGM was significantly higher than that of DDGS but not significantly different from CM. Apparent energy digestibility of DDGS was significantly lower than CGM but significantly higher than CM. Findings suggested that composition of the reference diet used in a digestibility trial affects the values of calculated ADCs, in addition to the chemical and physical attributes of the test ingredient.     

Utilization of kerosene by a hydrocarbon-assimilating strain of Fusarium oxisporum

Fusarium oxysporum IFO 6384 was grown in three different media, one containing glucose and two containing kerosene as carbon source. One of the kerosene media contained also Tween 60. The harvested dry mats were weighed at various stages of growth. Substitution of glucose with kerosene led to a sharp drop in the production of fungal mycelia. Analysis of the mat samples representing maximum yields indicated that the mycelia grown in the kerosene media were richer in free amino acid and poorer in protein as well as in polymeric and low-molecular weight carbohydrates than those grown in the glucose medium. Treatment of the culture filtrates with three volumes of acetone led to the separation of two fractions. In the first, acetone soluble fraction the free sugars and amino acids were determined, whereas the second, acetone precipitable one, was examined for its proteolytic activity. The gelatinase activity of the acetone precipitable material (APM) obtained from the kerosene media was lower than that from the glucose medium. The former activity, in contrast to the latter reached its maximum and minimum values at pHs 4 and 9, respectively.     

Influence of the soya meal fractions on gibberellic acid and gibberellin A production in submerse cultivation ofGibberella fujikuroi

The relationship of different soya meal components to gibberellin (GA) production was studied. Fluorometric assay confirmed that under the given fermentation conditions, only gibberellic acid (GA₃) was synthesized on medium containing corn steep. On substituting soya flour for corn steep, the same amount of GA₃ was produced and in addition gibberellin A (GA₁) was formed. The GA₃: GA₁ ratio was 1∶1. The course of fermentation in media containing the soya meal protein fraction (fraction I), the soya meal amino acid complex, the corn steep amino acid complex and individual amino acids (γ-aminobutyric acid or tryptophane) was the same as in the control medium containing soya meal. The soya meal fraction II, which is characterized by a high cellulose and carbohydrate content, raised GA production by 25% as compared with production in medium containling soya meal; it simultaneously stimulated GA₃ production, so that the final GA₃: GA₁ ratio was 4∶1.     

Improvement of clavulanic acid production by Streptomyces clavuligerus in medium containing soybean derivatives

The effect of the nitrogen source in the production medium on the level of clavulanic acid production by Streptomyces clavuligerus has been investigated. Batch cultures using two types of synthetic culture medium and two types of complex culture medium containing soybean derivatives were employed. To allow comparison of the various media, all of them were formulated with 4.0 g total nitrogen/l. It was observed that the production of clavulanic acid using synthetic medium reached values slightly greater than those usually found in the literature. However, in trials with complex media, it was found that when Samprosoy 90NB (protein extract of soybean) was utilized, production of clavulanic acid went up to 920 mg/l, twice as high as when soy meal was used, and notably higher than values reported in the literature (300–500 mg/l) for complex medium.     

Effect of technical threonine sources on homoserine biosynthesis by mutant Brevibacteruim flavum 2T

The effect of threonine technical sources on the homoserine biosynthesis by the threonine auxotroph Brevibacterium flavum 2T when cultivated on sucrose and acetic acid containing media was investigated. Various threonine sources (corn extract and fodder yeast, microbial biomass and soybean meal hydrolyzates) prepared by means of different hydrolyzing agents (acids, enzymes, autolysis) were used. The most effective substrate was protein--vitamin concentrate hydrolyzate, particularly combined with corn extract in the ratio 1: 0,25-0.5 (with respect to the dry weight of the initial material). The homoserine yield was 16.2 g/l on the sucrose containing medium and 18.4 g/l on the acetic acid containing medium which was in agreement with controls. The medium containing pure threonine was used as a control. With other threonine sources (corn extract, protein-vitamin concentrate autolyzate and enzymolyzate, fodder yeast and soybean meal hydrolyzates), the homoserine production was significantly lower, i.e. 40-70% of the control. The content of amino acids (threonine, isoleucine, methionine) in the initial material and their suitability for the homoserine biosynthesis were found to be correlated. The substrates with a high content of threonine (over 3.5%) and a low content of methionine (below 0.5%) proved most effective. The use of the material in which the ratio threonine: methionine was less than 6.0 caused the homoserine biosynthesis to be partially replaced with that of lysine.     

Oxygen uptake rate optimization with nitrogen regulation for erythromycin production and scale-up from 50 L to 372 m3 scale

Effects of different nitrogen sources on the erythromycin production were investigated in 50 l fermenter with multi-parameter monitoring system firstly. With the increase of soybean flour concentration from 27 g/l to 37 g/l to the culture medium, the erythromycin production had no obvious increase. Whereas adding corn steep liquor 15 g/l in the medium was beneficial for the production of erythromycin, the maximum erythromycin production was 22.2% higher than that of the control. It was found that corn steep liquor can regulate and enhance the oxygen uptake rate (OUR) which characterizes the activity of the microbial metabolism by inter-scale observation and data association. Both Intracellular and extracellular organic acids of central metabolism were analyzed, and it was found that the whole levels of lactic acid, pyruvic acid, citric acid, and propionic acid were higher than those of control before 64th h. The consumption amount of amino acids, which could be transformed into the precursors for erythromycin synthesis (i.e. threonine, serine, alanine, glycine and phenylalanine), were elevated compared with the control in erythromycin biosynthesis phase. The results indicated that corn steep liquor can regulate OUR to certain level in the early phase of fermentation, and enhance the metabolic flux of erythromycin biosynthesis. Erythromycin production was successfully scaled up from a laboratory scale (50 l fermenter) to an industrial scale (132 m(3) and 372 m(3)) using OUR as the scale-up parameter. Erythromycin production on industrial scale was similar to that at laboratory scale.     

Economic analysis of a modified dry grind ethanol process with recycle of pretreated and enzymatically hydrolyzed distillers' grains

A modification of the conventional dry grind process for producing ethanol from yellow dent corn is considered with respect to its economic value. Process modifications include recycling distillers' grains, after being pretreated and hydrolyzed, with the ground corn and water to go through fermentation again and increase ethanol yields from the corn starch. A dry grind financial model, which has been validated against other financial models in the industry, is utilized to determine the financial impact of the process changes. The hypothesis was that the enhanced process would yield higher revenues through additional ethanol sales, and higher valued dried distillers' grains (DDGS), due to its higher protein content, to mitigate the drop in DDGS yields. A 32% increase in net present value (NPV) for the overall operation is expected when applying the process modifications to a 100million gallon ethanol plant, and an enzyme cost of $0.20 for each additional gallon of ethanol produced. However, there may be no value added to the enhanced dried distillers' grains (eDDGS), even in light of its higher protein levels, as current pricing is expected to be more sensitive to the amino acid profile than the total protein level, and the eDDGS has lower lysine levels, a key amino acid. Thus, there is a decrease in revenue from eDDGS due to the combination of no price change and loss of DDGS yield to ethanol. The financial improvements are a result of the increased revenue from higher ethanol yields outpacing the sum of all added costs, which include higher capital costs, larger loan payments, increased operating costs, and decreased revenues from dried distillers' grains.     

Auxin production by plant-pathogenic pseudomonads and xanthomonads

Pathogenic strains of Xanthomonas campestris pv. glycines which cause hypertrophy of leaf cells of susceptible soybean cultivars and nonpathogenic strains which do not cause hypertrophy were compared for their ability to produce indole compounds, including the plant hormone indole-3-acetic acid (IAA) in liquid media with or without supplementation with l-tryptophan. Several additional strains of plant-pathogenic xanthomonads and pseudomonads were also tested for IAA production to determine whether in vitro production of IAA is related to the ability to induce hypertrophic growth of host tissues. Indoles present in culture filtrates were identified by thin-layer chromatography, high-performance liquid chromatography, UV spectroscopy, mass spectroscopy, and gas chromatography-mass spectrometry and were quantitated by high-performance liquid chromatography. All strains examined produced IAA when liquid media were supplemented with l-tryptophan. The highest levels of IAA were found in culture filtrates from the common bean pathogen Pseudomonas syringae pv. syringae, and this was the only bacterium tested which produced IAA without addition of tryptophan to the medium. Additional indoles identified in culture filtrates of the various strains included indole-3-lactic acid, indole-3-aldehyde, indole-3-acetamide, and N-acetyltryptophan. Pseudomonads and xanthomonads could be distinguished by the presence of N-acetyltryptophan, which was found only in xanthomonad culture filtrates.     

Optimization of growth and hydrolytic enzymes production by Fusarium culmorum using response surface method

Production of hydrolytic enzymes by a phytopathogenic fungus Fusarium culmorum was investigated. The proteolytic activity was observed when the fungus was grown in the medium containing starch or soybean meal as a carbon source. The amylolytic and lipolytic activities were not found. Response surface modeling was applied to shake-flask culture of the fungus to determine the optimum concentration of carbon source and optimal culture time for growth and protease production. The results indicated that the maximum yield of protease production corresponded to the concentration of soybean meal of 1.4?g/ml and culture time of 4.5?days. The fungus growth depends on the concentration of carbon source in the medium whereas the enzyme production was also influenced by the culture time and interaction between these two variables.     

Temperature and carbon source affect the production and secretion of a thermostable β-xylosidase by Aspergillus fumigatus

The effect of the temperature of growth and carbon source on the production and secretion of β-xylosidase (EC 3.2.1.37) by the thermotolerant fungi Aspergillus fumigatus was studied in submerged cultures. In cultures developed at optimal temperature (30 °C), the enzyme was predominantly cell-bound, while in cultures developed at higher temperature (42 °C), the β-xylosidase activity was predominantly found in the cell-free filtrates. The use of corn cob powder instead of xylan as substrate increased considerably the secretion of enzyme. The highest level of extracellular β-xylosidase (45 U/ml or 360 U/mg protein) was obtained in 3% corn cob cultures grown at 42 °C for 72 h. The partially purified enzyme was active and stable at high temperatures. The presence of high titres of β-xylosidase activity in association with xylanase in the culture filtrates enhanced the efficiency of the pulp hydrolysis process.     

Influence of Phospholipids on Growth, Sporulation and Virulence of the Endoparasitic Fungi Drechmeria coniospora, Verticillium balanoides and Harposporium anguillulae in Liquid Culture

Verticillium balanoides mycelial growth was stimulated on solid corn meal agar (1.7 %) and in liquid corn meal broth (0.2 %) upon the addition of phospholipids at various concentrations. Sporulation differed with phospholipid products and was highest in pure corn meal. Drechmeria coniospora mycelial growth increased upon addition of phospholipids at all concentrations in solid or liquid culture. Sporulation increased at high concentration (1000 ppm) and decreased at low concentration (100 ppm) of phospholipids in the medium. For both fungi, infectivity of conidia produced in liquid culture decreased when compared to conidia from parasitized nematodes. Addition of phospholipids partly restored this effect. Harposporium anguillulae mycelial growth and sporulation was not affected by addition of phospholipids to solid or liquid corn meal medium.     

Phenazine-1-carboxylic acid production in a chromosomally non-scar triple-deleted mutant Pseudomonas aeruginosa using statistical experimental designs to optimize yield

We constructed a non-scar triple-deleted mutant Pseudomonas aeruginosa to improve phenazine-1-carboxylic acid (PCA) yield and then optimized the culture conditions for PCA production. Using a non-scar deletion strategy, the 5′-untranslated region of the phz1 gene cluster and two genes, phzM and phzS, were knocked out of the P. aeruginosa strain M18 genome. The potential ability for high-yield PCA production in this triple-deleted mutant M18MSU1 was successfully realized by using statistical experimental designs. A 2^5–1 fractional factorial design was used to show that the three culture components of soybean meal, corn steep liquor and ethanol had the most significant effect on PCA production. Using a central composite design, the concentration of the three components was optimized. The maximum PCA production was predicted to be 4,725.1 mg/L. With the optimal medium containing soybean meal 74.25 g/L, corn steep liquor 13.01 g/L and ethanol 21.84 ml/L, a PCA production of 4,771.2 mg/L was obtained in the validation experiments, which was nearly twofold of that before optimization and tenfold of that in the wild-type strain. This non-scar triple-deleted mutant M18MSU1 may be a suitable strain for industrial production of this biologically synthesized fungicide due to its high PCA production, presumed safety, thermal adaptability and cost-effectiveness.