Enhanced nisin and pediocin production on whey supplemented with different nitrogen sources

Production of nisin and pediocin were followed, respectively, in Lactococcus lactis subsp. lactis CECT 539 and Pediococcus acidilactici NRRL B-5627 grown with lactose and four different nitrogen sources. Neither NH₄Cl nor glycine improved production of the bacteriocins. Both yeast extract and Casitone increased pediocin production from 55 BU ml^–1 to 195 BU ml^–1 and 185 BU ml^–1, respectively. Nisin increased from 21 BU ml^–1 to 74 BU ml^–1 and 59 BU ml^–1 with these nitrogen sources.     

An empirical method for describing the joint effects of environmental and other variables on crop yield

There is considerable interest in developing understanding of the spatial variation of crop yield within fields in relation to the spatial variation of environmental factors. Such understanding might allow inputs to crops to be used more efficiently by spatially variable application. The joint action of factors on crop yield (whether controlled treatments or environmental variables) may be additive, interactive or potentially limiting in the sense of von Liebig's “Law of the Minimum”. The nature of the joint action of an input and environmental factors has profound implications for the possibility of improving the efficiency of use of the input by spatially variable application. Conventional methods for analysing data on such factors and yield (e.g. multiple regression) make specific assumptions compatible only with a narrow range of permissible models. A procedure is proposed and demonstrated in this paper for the exploratory analysis of data from experiments and/or crop surveys in order to describe the joint action of important factors on crop yield. The procedure could be applied to specific experiments in order to indicate whether there is any scope for optimising rates of an input with respect to one or more spatially variable factors, and for indicating whether the relationship between the local optimum rate of the input and values of these factors is simple (factors act additively or in accordance with the Law of the Minimum) or complex (factors interact).     

An enzyme kinetic model for describing fermentation processes

An enzyme kinetic model has been proposed to describe fermentation processes. This type of model was chosen because it is biologically sound, can incorporate all of the important engineering control variables, and can draw upon, in its development, the extensive kinetic literature. An intial qualitative test for this model was made on the gluconic acid fermentation. A necessary check of the model was that Monod's empirical cell growth and yield equations were derived as a special case. The model also offered an explanation for the hysteresis behavior of the gluconic acid production rate as a function of gluconolactone.     

A function for describing nitrogen uptake and dry matter production by winter barley crops

The quantityY, of dry matter produced,Y _d , and nitrogen taken up,Y _n , during the growth of winter barley, was shown to be a function of thermal time,x,

Preliminary tests on nisin and pediocin production using waste protein sources. Factorial and kinetic studies

Lactic acid bacteria, the object of current interest as bacteriocin producers, are microorganisms with complex requirements for peptidic sources, making them appropriate indicators for testing the suitability of formulations based on proteinaceous wastes for use as microbiological media. Different peptones obtained from visceral and fish muscle residues promoted growth of lactic acid bacteria when applied individually or in combination. Kinetic parameters and bacteriocin production were similar and, in some cases (pediocin), far superior (>500%) to those obtained with bactopeptones and commercial media specifically recommended for lactic acid bacteria growth. Visceral residues, especially when subjected to a brief process of autohydrolysis at 20 degrees C, were more efficient for bacterial growth than muscle, even when muscle was treated with pepsin.     

Effect of complex nitrogen sources on the production of penicillin acylase byBacillus megaterium

The following complex nitrogen sources were evaluated for the production of penicillin acylase byBacillus megaterium: casein hydrolysate, corn steep liquor, stick water concentrate, blood meal and defatted sunflower meal. Experiments were run in shake flasks at 30‡C and pH 7.0. Best results were obtained with casein hydrolysate: 244 IU/I were produced with a productivity of 20.3 IU/l/h and yield of 717.6 IU/g of nitrogen. The lowest results correspond to sunflower meal with 39 IU/1.     

Effect of carbon and nitrogen sources on glucoamylase production inLactobacillus brevis

A strain ofLactobacillus brevis produced extracellular glucoamylase. Induction of the glucoamylase occurred when saccharides such as starch, dextrin, maltose, mannitol and sucrose were employed as sole carbon sources. Synthesis of the amylase also occurred when soybean extract and peptone were used as sole nitrogen sources. The organism could be employed as a starter culture for local food fermentation.     

碳源和氮源对5-酮基-葡萄糖酸生成的影响

氧化葡萄糖杆菌Gluconobacter oxydans可以将葡萄糖氧化成葡萄糖酸,并进一步氧化成2-酮基-葡萄糖酸(2KGA)和5-酮基-葡萄糖酸(5KGA),其中5KGA在催化剂的作用下能够转化为L(+)-酒石酸。为了提高5-酮基-葡萄糖酸产量,以仅生成5KGA的氧化葡萄糖杆菌Gluconobacter oxydans HGI-1为出发菌株,研究不同碳源(蔗糖、乳糖、麦芽糖、淀粉、葡萄糖)和有机氮源(酵母浸粉、鱼粉、玉米浆、黄豆饼粉、棉籽饼粉)对5KGA产量的影响。500 mL摇瓶试验结果表明,当葡萄糖浓度为100 g/L时,5KGA产量最高为98.20 g/L;当有机氮源为酵母浸粉、鱼粉和玉米浆,其添加量的蛋白含量为1.60%时,5KGA产量分别为100.20 g/L、109.10 g/L和99.83 g/L,其中,使用鱼粉的5KGA产量最高,使用玉米浆的5KGA产量比酵母浸粉略低。出于经济考虑,文中选择玉米浆作有机氮源,并在5 L发酵罐中进行分批发酵放大试验,5KGA的产量为93.80 g/L,最大生成速率为3.48 g/(L·h),平均生成速率为1.56 g/(L·h)。结果表明,葡萄糖和玉米浆分别为Gluconobacter oxydans HGI-1规模化生产5KGA的最适碳源和氮源,可利用葡萄糖几乎全部(85.93%)转化为5KGA。     

Effects of different nitrogen sources on lignocellulose degradation and APPL production

Naphthalene utilizing bacteria were isolated from several sites above and below the discharge from a coking plant. The distribution of the bacteria was influenced by the effluent. Of these isolates, 11·4% obtained from the effluent discharge site, contained plasmids. No conjugal transfer of naphthalene utilizing ability was observed in over 1000 matings. Curing and transformation experiments demonstrated that one plasmid pNB33 (101 kb) was concerned with naphthalene catabolism.     

Dose-response relationships. A model for describing interactions, and its application to the combined effect of nisin and lactic acid on Leuconostoc mesenteroides

As well as producing bacteriocins, many lactic bacteria produce other potentially toxic compounds or growth inhibitors, especially lactic acid, which may interfere in the assays commonly used to quantify these peptides. A systematic set of modifications is proposed which, when applied to the logistical equation, enable it to describe the combined (but not additive) effects of two or more active principles. The general model thus derived is applied to the interaction of nisin and lactic acid on Leuconostoc mesenteroides.     

Effects of different nitrogen sources on the biogas production - a lab-scale investigation

For anaerobic digestion processes nitrogen sources are poorly investigated although they are known as possible process limiting factors (in the hydrolysis phase) but also as a source for fermentations for subsequent methane production by methanogenic archaea. In the present study different complex and defined nitrogen sources were investigated in a lab-scale experiment in order to study their potential to build up methane. The outcome of the study can be summarised as follows: from complex nitrogen sources yeast extract and casamino acids showed the highest methane production with approximately 600ml methane per mole of nitrogen, whereas by the use of skim milk no methane production could be observed. From defined nitrogen sources l-arginine showed the highest methane production with almost 1400ml methane per mole of nitrogen. Moreover it could be demonstrated that the carbon content and therefore C/N-ratio has only minor influence for the methane production from the used substrates.     

氮源对蛹虫草生长及类胡萝卜素产生的影响

【背景】蛹虫草是一种珍稀食药用菌,类胡萝卜素不仅为其重要活性成分,而且影响子实体的外观品相,但是类胡萝卜素产生的影响因素不明。【目的】揭示氮源对蛹虫草生长和类胡萝卜素产生的影响。【方法】测定不同氮源培养基中菌株生长速度、分生孢子产生及类胡萝卜含量,筛选菌株生长的最适氮源,进一步研究不同浓度的氮源对蛹虫草生长及类胡萝卜素产生的影响,并测定不同光照条件下氮源浓度对蛹虫草子实体类胡萝卜素产生的影响。【结果】蛹虫草在不同的氮源培养基中菌落形态和类胡萝卜素产生存在明显差异。麦麸和黄豆粉培养基中菌株生长速度最快,但是菌落稀疏,正面分别呈现荧光黄色和极微弱红色;蛋白胨和酵母提取物培养基中菌落致密,产孢量极显著高于其它氮源培养基(P0.01),菌落正面为橙黄色;甘氨酸和柠檬酸为氮源时完全没有色素产生,其它无机和氨基酸氮源培养基平板背面有微量色素产生。固体和液体静置培养条件下均发现蛋白胨浓度在0-3%的范围内,随着浓度的增加,类胡萝卜素含量增加;子实体栽培中不同的氮源浓度均表现为蓝光光照条件下类胡萝卜素含量显著高于白光;而在白光和蓝光光照条件下均表现为蛋白胨浓度为1%时类胡萝卜素含量最高,分别为2 809.38±386.24μg/g和4 093.75±518.37μg/g。【结论】氮源种类和浓度显著影响蛹虫草类胡萝卜素的产生,蓝光光照和1%蛋白胨浓度为子实体类胡萝卜素产生的最佳条件,这为栽培富含类胡萝卜素的蛹虫草子实体提供了试验依据。     

The effect of nisin concentration and nutrient depletion on nisin production of Lactococcuslactis

The kinetics of nisin production was studied in batch cultures using a construct of Lactococcuslactis subsp. lactis C2SmPrt⁻, containing a transposon (TnNip) that encodes nisin production. The introduction of TnNip into C2SmPrt⁻significantly lowered the specific growth rate and the maximum A ₆₂₀ reached was reduced from 15.2 to 11.0. The effect of nisin concentration and nutrient depletion on nisin production of the construct, C2SmPrt⁻(TnNip), was examined. Nisin production was found to be inhibited by high concentrations of nisin, when grown in excess nutrient, even though growth of the culture continued because nutrient limitation was not operating. However, in low nutrient concentrations nisin production was limited by nutrient depletion. The specific growth rate of C2SmPrt⁻(TnNip) was altered, by using different nutrient concentrations and different sugars, in order to examine the relationship between nisin production and growth. Nisin production was shown to be growth-associated for most of growth, but near the end of growth, when the specific growth rate was 0.05 h⁻¹ or less, the production ceased. Received: 20 March 1997 / Received revision: 10 June 1997 / Accepted: 14 June 1997     

A function for describing nitrogen uptake,dry matter production and rooting by wheat crops

The quantities,Y, of nitrogen taken up, and dry matter produced, at various times during the growth of six winter wheat crops at Rothamsted were shown to be related to thermal time,x, based on soil temperature, by a simple equation $$Y = (A^{ - 1/n} + \exp ( - kx))^{ - n} $$ whereA is the ultimate maximum ofY, n a shape factor andk a rate constant that is related toA andn throughx′, the inflexion point of the function. The value ofn was 1.5 for both N uptake and dry matter. The value ofA for N uptake,A _N , was well described by a multiple regression on sowing data,t _s , expressed as the number of days after August 31st, and rainfall,R _Apr , in the April before harvest, but no such regression could be found for the value ofA for dry matter,A _D . The rate constants,k _N andk _D , for N-uptake and dry-matter production respectively, could be related to the date of sowing and the weather through the corresponding inflexion points,x′ _N andx′ _D . Highly significant regressions were found, forx′ _N on the time,t _sf , between sowing and the return of the soil to field capacity and forx′ _D on the reciprocal oft _s . The function was used to generate N uptake curves from values ofA _N andk _N (obtained fromx′ _N ) given by inserting the appropriate values ofR _Apr ,t _s andt _sf in the regressions. These fitted measured N uptakes satisfactorily for the six crops used to obtain the regressions, and four grown subsequently, at Rothamsted, and also for six crops at Woburn. Values ofA _D had to be set arbitrarily because no regression had been found to predict them, but using these arbitrary values in the function gave dry matter curves that fitted the measurements satisfactorily for all ten Rothamsted crops and two of the Woburn crops. Tests for seasonal and site effects showed thatA _N was influenced more by differences between the two sites than by seasonal differences other than those inR _Apr , whereasA _D was strongly influenced by these seasonal differencess and very little by those between the sites.     

Effect of carbon and nitrogen sources on the production of penitrem B byPenicillium aurantiogriseum

Effect of different carbon and nitrogen sources on the production of penitrem B was studied.d-Xylose induced maximum penitrem B production, while melibiose, glycerol, citric acid and succinic acid were poor substrates. Potassium nitrate,l-asparagine, sodium nitrate, glycine,dl-aspartic acid andl-tryptophan supported good production of penitrem B. Conversely zirconyl nitrate, barium nitrate, aluminum nitrate, acetanilide, 4-aminobenzoic acid, 4-nitrobenzoic acid and 4-nitroaniline were toxic and did not even permit the growth of the fungus.