High yield mixotrophic cultures of the marine microalga Tetraselmis suecica (Kylin) Butcher (Prasinophyceae)

The effects of three organic compounds were tested on one of the most used marine micro-algae in the aquaculture of molluscs and crustaceans, Tetraselmis suecica. Studies were made in axenic conditions with yeast extract, peptone and glucose added to the culture medium, each alone, in combinations of two or all together. Medium without any organic compound was used for the control. Cultures containing yeast extract grew best, reaching maximum cell density of 3.79 × 10⁶ and 3.84 × 10⁶ cells ml⁻¹. The organic carbon source affected the biochemical composition. The components most affected were the carbohydrates, with values between 6.5 pg cell⁻¹ in control cultures and 48.5 pg cell⁻¹ in glucose cultures. Protein content ranged between 27.5 pg cell⁻¹ in control cultures and 88.6 pg cell⁻¹ in yeast + glucose + peptone cultures. The lipid content changed little. Maximum protein yields were reached in cultures with yeast + glucose and with yeast - glucose - peptone, with values of 24.6 and 28.2 mg 1⁻¹ d⁻¹, respectively. These values are 22 and 25 times those in control cultures. A maximum carbohydrate yield of 7.9 mg carbohydrate per litre per day was obtained in yeast + glucose + peptone cultures, 27 times that in the control cultures. The maximum lipid yield was obtained with yeast + glucose + peptone and yeast + glucose. Maximum energy values were 308 kcal 1⁻ in yeast extract - glucose - peptone cultures and 279 kcal 1⁻¹ in yeast extract + glucose cultures. Gross energy values in control cultures were 24.5 kcal 1⁻¹, but peptone cultures presented the minimum energy value, 22 kcal 1⁻¹. The yeast extract: glucose ratio in the culture medium was optimized. A ratio 2:1 produced the best yields in cells, protein, carbohydrate and gross energy.     

Wild rice as fermentation substrate for mycotoxin production

Many cereal grains have been studied for their suitability as substrates for the fermentative production of mycotoxins. However, except for aflatoxin, wild rice has not been investigated. Hence, five mold cultures known to produce the mycotoxins ochratoxin-A, penicillic acid, patulin, vomitoxin, and zearalenone were grown on wild rice under varying conditions of moisture and temperature to determine whether this grain would serve as a suitable substrate for toxin production. Under appropriate fermentation conditions, good yields of ochratoxin-A and moderate amounts of patulin were obtained, but only small amounts of penicillic acid, vomitoxin, and zearalenone were elaborated. An extract from a sample of naturally molded wild rice contained 0.8 microgram of patulin per g of rice. The predominating mold was identified as Aspergillus clavatus. Under identical cultural conditions, this isolate and a known patulin-producing strain of A. clavatus yielded approximately equivalent amounts of the mycotoxin.     

Wild rice as fermentation substrate for mycotoxin production.

Many cereal grains have been studied for their suitability as substrates for the fermentative production of mycotoxins. However, except for aflatoxin, wild rice has not been investigated. Hence, five mold cultures known to produce the mycotoxins ochratoxin-A, penicillic acid, patulin, vomitoxin, and zearalenone were grown on wild rice under varying conditions of moisture and temperature to determine whether this grain would serve as a suitable substrate for toxin production. Under appropriate fermentation conditions, good yields of ochratoxin-A and moderate amounts of patulin were obtained, but only small amounts of penicillic acid, vomitoxin, and zearalenone were elaborated. An extract from a sample of naturally molded wild rice contained 0.8 microgram of patulin per g of rice. The predominating mold was identified as Aspergillus clavatus. Under identical cultural conditions, this isolate and a known patulin-producing strain of A. clavatus yielded approximately equivalent amounts of the mycotoxin.     

Effect of yeast extract concentration on growth ofSchizoccharomyces pombe

Summary The effect of yeast extract on the growth ofSchizosaccharomyces pombe was investigated using a complex-synthetic medium. Batch cultures at low-glucose concentration show that a too low concentration of yeast extract may limit the biomass formation. On this medium kinetics and yields were found to be similar to those obtained on a synthetic-defined medium under both aerobic and anaerobic conditions.     

Growth yield from electrons available from substrates in aerobic- and photoheterotrophic cultures of Rhodopseudomonas sphaeroides S

A balance of electrons available from acetic acid consumed for growth and oxygen uptake in the aerobic- and photoheterotrophic growth of Rhodopseudomonas sphaeroides S on acetate-minimal medium could be realized the same as in the carbon balance. The unmeasured amounts of yeast extract consumed by the cells grown on propionate–yeast extract media were indirectly estimated from the balance equation of electrons available from carbon substrates. The specific consumption rate of the yeast extract increased with an increase in propionate consumption rate in aerobic and photoheterotrophic cultures. Growth yields from acetic acid and from propionic acid plus yeast extract were calculated on the electron level, i.e., Y_X/ave g cell produced/equivalent electrons available from substrate consumed. Y_X/ave values were 5.0 to 5.8 g cell/ave in photoheterotrophic cultures and 2.7 to 3.6 in aerobic–heterotrophic cultures regardless of different medium compositions.     

Use of Cheese Whey for Vitamin B12 Production: I. Whey Solids and Yeast Extract Levels1

The suitability of cheese whey as a substrate for vitamin B(12) production by Propionibacterium shermanii was studied. It was found that with a given level of whey solids a definite amount of yeast extract was required to give maximal yields of vitamin B(12). Of the levels of materials studied, 10% whey solids and 1.5% yeast extract gave the best yields of vitamin B(12). Most of the lactose of the whey had been utilized in all flask cultures after 168 hr at 29 C.     

Metabolomic alterations in elicitor treated Silybum marianum suspension cultures monitored by nuclear magnetic resonance spectroscopy

A comprehensive metabolomic profiling of Silybum marianum (L.) Gaernt cell cultures elicited with yeast extract or methyl jasmonate for the production of silymarin was carried out using one- and two-dimensional nuclear magnetic resonance spectroscopy. With these techniques we were able to detect both temporal quantitative variations in the metabolite pool in yeast extract-elicited cultures and qualitative differences in cultures treated with the two types of elicitors. Yeast extract and methyl jasmonate caused a metabolic reprogramming that affected amino acid and carbohydrate metabolism; upon elicitation sucrose decreased and glucose levels increased, these changes being dependent on "de novo" protein synthesis. Also dependent on protein synthesis were the increase seen in alanine and glutamine in elicited cultures. Yeast extract differentially acted on threonine and valine metabolism and promoted accumulation of choline and alpha-linolenic acid in cells thus suggesting its action on membranes and the involvement of the octadecanoid pathway in the induction of silymarin in S. marianum cultures. Phenylpropanoid metabolism was altered by elicitation but, depending on elicitor, different phenylpropanoid profile was produced. The results obtained in this study will permit in the future to identify candidate components of the signalling pathway involved in the stimulation of the constitutive pathway of silymarin.     

Influence of the nitrogen source on Saccharomyces cerevisiae anaerobic growth and product formation.

To prevent the loss of raw material in ethanol production by anaerobic yeast cultures, glycerol formation has to be reduced. In theory, this may be done by providing the yeast with amino acids, since the de novo cell synthesis of amino acids from glucose and ammonia gives rise to a surplus of NADH, which has to be reoxidized by the formation of glycerol. An industrial strain of Saccharomyces cerevisiae was cultivated in batch cultures with different nitrogen sources, i.e., ammonium salt, glutamic acid, and a mixture of amino acids, with 20 g of glucose per liter as the carbon and energy source. The effects of the nitrogen source on metabolite formation, growth, and cell composition were measured. The glycerol yields obtained with glutamic acid (0.17 mol/mol of glucose) or with the mixture of amino acids (0.10 mol/mol) as a nitrogen source were clearly lower than those for ammonium-grown cultures (0.21 mol/mol). In addition, the ethanol yield increased for growth on both glutamic acid (by 9%) and the mixture of amino acids (by 14%). Glutamic acid has a large influence on the formation of products; the production of, for example, alpha-ketoglutaric acid, succinic acid, and acetic acid, increased compared with their production with the other nitrogen sources. Cultures grown on amino acids have a higher specific growth rate (0.52 h-1) than cultures of both ammonium-grown (0.45 h-1) and glutamic acid-grown (0.33 h-1) cells. Although the product yields differed, similar compositions of the cells were attained. The NADH produced in the amino acid, RNA, and extracellular metabolite syntheses was calculated together with the corresponding glycerol formation. The lower-range values of the theoretically calculated yields of glycerol were in good agreement with the experimental yields, which may indicate that the regulation of metabolism succeeds in the most efficient balancing of the redox potential.     

Byssotoxin A, a secondary metabolite of Byssochlamys fulva.

Byssochlamys fulva, isolated from corn, was grown on nutrient-amended shredded wheat medium for 14 days at 25 C. Crude solvent extract from these cultures was toxic to brine shrimp, chicken embryos, and rats. The extract was slightly inhibitory to the germination of of pea seeds, but was nontoxic to ten species of bacteria and one of yeast. One metabolite was isolated, given the trivial name byssotoxin A, and partially characterized chemically and physically.     

Optimization studies for the bioconversion of Jerusalem artichoke tubers to ethanol and microbial biomass

Summary A total of 8 yeast and microbial cultures have been grown in the extract derived from the tubers of Jerusalem artichoke (Helianthus tuberosus) and screened according to the following optimization criteria: rates and yields of ethanol production, rates and yields of biomass production, and % of original sugars utilized during fermentation. Batch growth kinetic parameters were also determined for the cultures studied.     

Comparative study of aflatoxins M1 and B1 production in solid-state and shaking liquid cultures

Production of aflatoxins M1 (AFM) and B1 (AFB) by Aspergillus flavus NRRL 3251 in solid-state and shaking liquid cultures using rice as the carbon source was compared. In general, solid-state cultures produced more aflatoxins than shaking liquid cultures on an equal rice weight basis. Solid-state cultures with continuous shaking yielded higher levels of toxins than those with intermittent shaking. However, intermittent shaking is a feasible replacement for the continuous shaking method for AFM production. A typical solid rice culture supplemented with yeast extract produced 30 and 2600 mg per kg rice of AFM and AFB, respectively, in 8 days at 29 degrees C. The optimal culture conditions for toxin production in a shaking liquid culture were also studied. Parameters under consideration included the amount of carbon (rice) and nitrogen source, initial medium pH, and aeration rate. At optimum conditions, a representative shaking liquid culture produced 18 and 1680 mg per kg rice of AFM and AFB, respectively, in 5 days at 29 degrees C. This shaking liquid culture appears feasible for scaling up and routine production of AFM and AFB for toxicological investigations.     

Organic nutrition of Beggiatoa sp.

Culture OH-75-B of Beggiatoa sp. differed significantly from any described previously in its utilization of organic carbon and reduced sulfur compounds. It deposited internal sulfur granules characteristic of Beggiatoa sp. with either sulfide or thiosulfate in the medium. This strain (OH-75-B, clone 2a) could be grown in agitated liquid cultures on mineral medium with acetate as the only source of organic carbon. The resultant growth yields and rates were comparable to those for typical heterotrophs. Of the other simple organic compounds tested, only pyruvate, lactate, or ethanol could singly support the growth of this strain. Single sugars or amino acids neither supported growth nor enhanced it when added to acetate-containing medium. In contrast, compounds of the tricarboxylic acid cycle enhanced growth yields when tested in concert with acetate. These and fluoroacetate inhibition results indicate that Beggiatoa sp. possesses a functional tricarboxylic acid cycle. Poor yields characterized the growth of this strain on dilute yeast extract medium, and higher concentrations of yeast extract proved inhibitory. The enzyme catalase, contrary to the findings of others, had no synergistic influence on growth yields when added to medium containing yeast extract or acetate or both.     

Nutritional evaluation of Cyanobacterium (Nostoc sp.) extract in Rhizobium cultures

Extracts from Nostoc sp. biomass (CE) were compared with yeast extract (YE) in the formulation of media for cultivation of Rhizobium etli and Bradyrhizobium japonicum. Growth depended on the rhizobium strain and also on the type and concentration of the extract. The growth kinetics of R. etli were substantially influenced by the addition of CE an YE at concentrations between 0.3 and 1% (w/v); cultures containing YE showed shorter lag periods and higher growth rates and those with CE presented higher growth yields. Depending on the extracts, a different behaviour was displayed by the cultures at the stationary phase; cell viability increased or remained fairly constant in cultures developed on CE, and those developed on high concentrations of YE showed a decline in viable cell counts.     

Nutritional evaluation of Cyanobacterium (Nostoc sp.) extract in Rhizobium cultures

Extracts from Nostoc sp. biomass (CE) were compared with yeast extract (YE) in the formulation of media for cultivation of Rhizobium etli and Bradyrhizobium japonicum. Growth depended on the rhizobium strain and also on the type and concentration of the extract. The growth kinetics of R. etli were substantially influenced by the addition of CE an YE at concentrations between 0.3 and 1% (w/v); cultures containing YE showed shorter lag periods and higher growth rates and those with CE presented higher growth yields. Depending on the extracts, a different behaviour was displayed by the cultures at the stationary phase; cell viability increased or remained fairly constant in cultures developed on CE, and those developed on high concentrations of YE showed a decline in viable cell counts.     

Yeast extract and methyl jasmonate-induced silymarin production in cell cultures of Silybum marianum (L.) Gaertn

The biosynthesis of the flavonolignan silymarin, a constitutive compound of the fruits of Silybum marianum with strong antihepatotoxic and hepatoprotective activities, is severely reduced in cell cultures of this species. It is well known that elicitation is one of the strategies employed to increase accumulation of secondary metabolites. Our study here reports on the effect of several compounds on the production of silymarin in S. marianum cultures. Yeast extract (YE), chitin and chitosan were compared with respect to their effects on silymarin accumulation in S. marianum suspensions and only yeast extract stimulated production. Jasmonic acid (JA) potentiated the yeast extract effect. One of the jasmonic acid derivatives, methyl jasmonate (MeJA), strongly promoted the accumulation of silymarin. Methyl jasmonate acted in a number of steps of the metabolic pathway of flavonolignans and its stimulating effect was totally dependent of "de novo" protein synthesis. Chalcone synthase (CHS) activity was enhanced by methyl jasmonate; however there did not appear to be a temporal relationship between silymarin accumulation and increase in enzyme activity. Also, this increase was not blocked by the protein synthesis inhibitor cycloheximide (CH). This study indicates that elicitor treatment promotes secondary metabolite production in S. marianum cultures and that jasmonic acid and its functional analogue plays a critical role in elicitation.     

The effect of culture medium composition and incubation time on synthesis of gibberellin-like substances by bacteria isolated from the roots of pine seedlings (Pinus silvestris L.)

It was found that synthesis of gibberellin-like substances by ten strains of Coryneform bacteria isolated from the roots of pine seedlings depended on both the composition of the medium and incubation time. More of these substances were produced in mineral medium with glucose in complex medium with casamino acids and yeast extract. Most gibberellin-like substances were found in 7 or 14-day old cultures. Culture supernatant fluids of most of the bacteria tested contained several gibberellin-like substances which on chromatograms run with the solvent system benzene, acetic acid (10:3, v/v) were located at Rf 0.0-0.3; 0.4-0.6 and 0.8-1.0.     

Rearing of the pupal parasitoid Brachymeria intermedia on veal homogenate-based artificial diets: evaluation of factors affecting effectiveness

The pupal parasitoid Brachymeria intermedia (Nees) was reared from egg to fecund adult on various veal homogenate-based artificial diets. For every replicate 12.12 ml of each diet were used. Four diets were tested first. Two media, one devoid of and one supplemented with 1 ml Galleria mellonella pupal extract, contained 0.19 g wheat germ and 0.19 g yeast extract each. The other two, one added with and the other devoid of host extract, contained 0.38 g yeast extract each and no wheat germ. All diets also contained chicken egg yolk (1.1 and 0.8 ml in the diets without and with host extract, respectively). The amount of yeast extract was seen to have no significant effect on any of the developmental parameters considered. The replacement of wheat germ with yeast extract was therefore not convenient, considering that the former is far more economical than the latter. Pupal extract was instead found to have a significant effect on pupal and adult yields. The highest adult yield (= 53.2%) was obtained on the diet supplemented with 0.38 g yeast extract and containing host pupal extract. A further four media, each comprising a different kind of material derived from G. mellonella, were subsequently tested. Adult yields were such as to suggest the possibility of replacing pupal with larval extract in the diets as the latter is easier to prepare since there are no cocoons to be removed. In contrast, when the diets were supplemented with larval or pupal homogenate, adult yields dramatically dropped. When B. intermedia was reared in groups rather than individually, most larvae died before attaining maturity. Only two parasitoids, in two different replicates, emerged as adults.     

不产桔霉素的红曲霉菌种深层发酵生产莫纳可林K

对三株在YES培养基中不产桔霉素的红曲霉菌种,在摇瓶中研究了它们液体发酵生产莫纳可林K的情况。在大米粉培养基中,红色红曲霉不产莫纳可林K,但是紫色红曲霉和烟灰色红曲霉均能产莫纳可林K,前者产量高于后者。在葡萄糖．甘油培养基中,后两者的产量均很低,但是如果在该培养基中添加酵母膏,紫色红曲霉能产生较为可观的莫纳可林K。在2L的发酵罐中,利用添加了酵母膏的葡萄糖-甘油培养基,紫色红曲霉在第13d的莫纳可林K产量可达104mg/L,培养过程中无桔霉素产生。     

Astaxanthin synthesis by Xanthophyllomyces dendrorhous DSM 5626 and its mutants on carrot extract medium under different illumination intensity

The effect of illumination intensity on astaxanthin synthesis by yeast Xanthophyllomyces dendrorhous DSM 5626 and its 4 mutants grown in cultures on carrot extract medium was investigated. Cell concentration, total carotenoid and astaxanthin yields were assessed in obtained cultures. Collected data were used to construct regression models describing the effect of illumination intensity on controlled parameters. Maximum cellular (0.44–0.46 g/kg of dry cell weight) and volumetric yields (2.3–2.4 mg/L) of the pigment were observed for mutants 10BE and 34B at 600 lx, as well as for mutant 26UV at 1000 lx. The highest yield of astaxanthin for the parental strain was obtained in culture at illumination of 1000 lx (0.29 g/kg of dry cell weight and 1.51 mg/L). The values of illumination determined on the basis of constructed regression models for individual yeast strains, at which astaxanthin synthesis should be the most efficient, remained within the range of 660–1000 lx.     

Effect of some nutritional and environmental parameters on the production of diacetyl and on starch consumption by Pediococcus pentosaceus and Lactobacillus acidophilus in submerged cultures

Three series of 5-day submerged cultures with Pediococcus pentosaceus MITJ-10 and Lactobacillus acidophilus Hansen 1748 were carried out in starch-based media, and the effect of cultural factors on the changes of starch, diacetyl and amylase activity determined. In axenic cultures, Ped. pentosaceus MITJ-10 produced more diacetyl (63.27 mg l(-1)) by adding glucose, yeast extract and CaCO3 (P < 0.01), at 28 degrees C (P < 0.05); but more starch was consumed (18.4 g l(-1)) in the absence of glucose (P < 0.01). Lact. acidophilus Hansen 1748 consumed more starch (26.56 g l(-1)) at 28 degrees C, with CaCO3, glucose (P < 0.01) and yeast extract (P < 0.05); however, the amylolytic activity (10077U l(-1)) was favoured at 35 degrees C (P < 0.01). Little starch was consumed in mixed cultures due to the low pH; nevertheless, diacetyl content rose to 135.76 mg l(-1) at 32 degrees C (P < 0.01). Therefore, both studied strains might be useful to produce aromatic extensors from starchy substrates. These natural aromatic extensors are of interest to the food industry.