Characterization of a Symbiotic Coculture of Clostridium thermohydrosulfuricum YM3 and Clostridium thermocellum YM4

Clostridium thermohydrosulfuricum YM3 and C. thermocellum YM4 were isolated from a coculture which was obtained from an enrichment culture inoculated with volcanic soil in Izu Peninsula, Japan. Strain YM3 had advantages over reported C. thermohydrosulfuricum strains in that it fermented inulin and could accumulate ethanol up to 1.3% (wt/vol). The highest ethanol yield obtained was 1.96 mol/mol of anhydroglucose unit in cellobiose. Strain YM4 had features different from those reported in C. thermocellum strains: it formed spores rarely (at a frequency of <10^-5), it required CO₂ and Na₂CO₃ for growth, and it fermented sucrose. Strain YM4 completely decomposed 1% Avicel within 25 h when the inoculum constituted 2% of the culture medium volume, and it produced 0.22 U of Avicelase and 2.21 U of carboxymethylcellulase per ml of the medium. The doubling times on Avicel, cellobiose, and glucose were 2.7, 1.1, and 1.6 h, respectively. Reconstructed cocultures of strains YM3 and YM4 were very stable and degraded Avicel more rapidly than did strain YM4 monoculture. Without yeast extract, neither microorganism was able to grow. However, the coculture grew on cellulose without yeast extract and produced ethanol in high yield. Moreover, cell-free spent culture broth of strain YM3 could replace yeast extract in supporting the growth of strain YM4. The symbiotic relationship of the two bacteria in cellulose fermentation is probably a case of mutualism.     

Characteristics of Protease Production by Cephalosporium sp

We investigated protease formation by Cephalosporium sp. strain KM388, which produced trypsin inhibitor in the same cultures, in medium containing polypeptone, meat extract, and glucose (natural medium) and in medium containing NaNO₃, glucose, and yeast extract (semisynthetic medium). In natural medium, protease was secreted into the culture broth after cessation of growth caused by consumption of the polypeptone, the growth-limiting substrate. Enzyme formation in the stationary growth phase was due to de novo and so-called preferential synthesis, because cycloheximide immediately inhibited enzyme formation. In semisynthetic medium, protease was produced in parallel with mycelial growth, but production was repressed by the addition of polypeptone to the medium; protease production began after the added polypeptone was consumed. On the other hand, if glucose was eliminated from natural medium, the lag period of initiation of enzyme production was reduced until the late exponential phase. The addition of phosphate up to a concentration of 1.0% to natural medium also shortened the lag period and damped the pH change of the broth during cultivation.     

Effect of culture conditions on mycelial growth, antibacterial activity, and metabolite profiles of the marine-derived fungus Arthrinium c.f. saccharicola

The effects of culture conditions and competitive cultivation with bacteria on mycelial growth, metabolite profile, and antibacterial activity of the marine-derived fungus Arthrinium c.f. saccharicola were investigated. The fungus grew faster at 30°C, at pH 6.5 and in freshwater medium, while exhibited higher antibacterial activity at 25°C, at pH 4.5, 5.5, and 7.5, and in 34 ppt seawater medium. The fungus grew faster in a high-nitrogen medium that contained 0.5% peptone and/or 0.5% yeast extract, while exhibiting higher bioactivity in a high-carbon medium that contained 2% glucose. The fungal growth was inhibited when it was co-cultured with six bacterial species, particularly the bacterium Pseudoalteromonas piscida. The addition of a cell free culture broth of this bacterium significantly increased the bioactivity of the fungus. Metabolite profiles of the fungus revealed by gas chromatography (GC)-mass spectrometry showed clear difference among different treatments, and the change of relative area of three peaks in GC profile followed a similar trend with the bioactivity variation of fungal extracts. Our results showed clear differences in the optimal conditions for achieving maximal mycelial growth and bioactivity of the fungus, which is important for the further study on the mass cultivation and bioactive compounds isolation from this fungus.     

Optimization of Low-Cost Culture Media for the Production of Biomass and Bacteriocin by a Urogenital Lactobacillus salivarius Strain

The aim of this work was to formulate a culture medium of lower cost than conventional laboratory media, in order to simultaneously obtain high amounts of both biomass and bacteriocin of vaginal Lactobacillus salivarius CRL 1328. The growth assays under different culture conditions were performed by using a 2^8?2 central composite experimental design, with a central point and sixteen additional points. The factors taken into consideration were glucose, lactose, yeast extract, tryptone, ammonium citrate, sodium acetate, MgSO₄ and MnSO₄. The simultaneous presence of a carbon source (mainly glucose), a nitrogen source (mainly yeast extract) and salts (mainly MnSO₄, MgSO₄ and sodium acetate) allowed the highest cell biomass and bacteriocin levels to be reached in the experimental design. Through the application of the desirability function, several optimal medium compositions to achieve efficient production of biomass and bacteriocin were predicted. The optimized growth media allow a cost reduction of around 25 to 40% compared with conventional broths. The results obtained represent an advance in the search of the most suitable strategies for the production of bioactive compounds for pharmaceutical products to prevent or treat female urogenital infections.     

Methanogenic digestion of glucose plus yeast extract by a defined bacterial consortium: Carbon balances and growth yields in chemostat culture

A methanogenic consortium of bacteria, isolated from anaerobic sewage sludge by growth on glucose and yeast extract and mineral salts, consisted of two strict anaerobes, one of which (the GD strain) degraded glucose and the other was a methanogen. In addition the consortium contained a small population of facultative anaerobes (4 types) which constituted <1% of the total biomass.In glucose-limited chemostat cultures of the consortium, the maximum methane output rate occured with a dilution rate (D) of 0.1 h⁻¹. With D = 0.10 h⁻¹ the consortium fermented both the glucose and yeast extract giving the following C balance (% C of glucose and yeast extract in the products): acetate, 34.2; biomass, 25.4; CO₂, 13.8; CH₄, 6.5; ethanol, 7.9; butyrate, 7.3; propionate, 3.2 (C recovery, 98.3%; H₂ production, 0.04 mol/Cmol substrate.The GD strain in uncontaminated culture fermented glucose only and gave the following C balance in a glucose-limited steady state chemostat culture with D=0.12 h⁻¹ (% glucose C in the products): acetate, 35.1; ethanol, 23.1; CO₂, 20.6; biomass, 12.3; butyrate, 4.4; propionate, 1.7 (C recovery, 97.2%); H₂ production, 0.293 mol/C mol glucose.The maximum growth yields (Y_G) from the C sources were 0.139 and 0.292 (C-mol biomass/C-mol substrate) for the GD organism and the consortium respectively.The maintenance energies were remarkably small compared with that typical of aerobic bacteria. This prompts the suggestion that the main function of maintenance energy substrate in aerobes is not to provide ATP but rather reducing equivalents to protect cells against O₂ damage. It is concluded that, in the technology of methanogenic conversion of wastes, besides the acidogenic and methanogenic stages, a third stage, for digestion of the biomass formed is required, otherwise the biomass can account for 25% of the substrate C supplied.     

Optimization of culture conditions for the bioconversion of vitamin D3 to 1α,25-dihydroxyvitamin D3 usingPseudonocardia autotrophica ID 9302

We assessed the ability of aPseudonocardia sp. from soil samples to bioconvert vitamin D₃. The optimal culture conditions for the bioconversion of vitamin D₃ to active 1α,25-dihydroxyvitamin D₃ were investigated by varying the carbon and nitrogen sources, the metal salt concentrations, the initial pH, and the temperature. Microbial transformations were carried out with the addition of vitamin D₃ dissolved in ethanol. They were sampled by extraction with methanol-dichloromethane and the samples were examined by HPLC. Optimum culture conditions were found to be 0.4% yeast extract, 1% glucose, 3% starch, 1% fish meal, 0.2% NaCl, 0.01% K₂HPO₄, 0.2% CaCO₃, 0.01% NaF, and pH 7.0 at 28°C. The optimal timing of the addition of vitamin D₃ for the production of calcitriol byPseudonocardia autotrophica ID 9302 was concurrent with the inoculation of seed culture broth. Maximum calcitriol productivity and the yield of bioconversion reached a value of 10.4 mg/L and 10.4% respectively on the 7th day in a 75 L fermenter jar under the above conditions.     

Characterization of optimal growth conditions and carotenoid production of strain Rhodotorula mucilaginosa HP isolated from larvae of Pieris rapae

Yeasts have been studied because of their production of a pigment known as carotenoid with potential application in food and feed supplements. A carotenoid‐producing yeast was isolated from the larvae of Pieris rapae, named HP. The strain HP was identified as Rhodotorula mucilaginosa classified by its carbohydrate fermentation pattern and physiological tests. Rhodotorula mucilaginosa HP produces several exogenous enzymes: alkaline phosphatase, esterase, leucine arylamidase, valine arylamidase, acid phosphatase and β‐glucosidase. Using response surface methodology, selected medium components (yeast extract, malt extract, peptone, glucose) were tested to find the optimum conditions for carotenoid production and the growth of R. mucilaginosa HP. Central composite design was used to control the concentrations of medium components. Peptone and glucose had the largest effects on carotenoid production and cell growth of R. mucilaginosa HP, respectively. The estimated optimal growth conditions of R. mucilaginosa HP were: yeast extract 3.23%, malt extract 2.84%, peptone 6.99% and glucose 12.86%. The estimated optimal conditions for carotenoid production were: yeast extract 2.17%, malt extract 2.11%, peptone 5.79% and glucose 12.46%. These results will assist in the formulation of an appropriate culture medium for optimal carotenoid production of R. mucilaginosa HP for commercial use.     

Semi-industrial Scale Production of a New Yeast with Probiotic Traits, <Emphasis Type="Italic">Cryptococcus</Emphasis> sp. YMHS,Isolated from the Red Sea

A new yeast strain with promising probiotic traits was isolated from the Red Sea water samples. The isolate (YMHS) was subjected to genetic characterization and identified as Cryptococcus sp. Nucleotide sequence analysis of the rRNA gene internal transcribed spacer regions showed 95% sequence similarity between the isolate and Cryptococcus albidus. Cryptococcus sp. YMHS exhibited desirable characteristics of probiotic microorganisms; it has tolerance to low pH in simulated gastric juice, resistance to bile salts, hydrophobic characteristics, broad antimicrobial activity, and in vitro ability to degrade cholesterol. The isolate grew well in a semi-defined medium composed of yeast extract, glucose, KH₂PO₄, (NH₄)₂SO₄, and MgSO₄, yielding cell mass of 2.32 and 5.82 g/l in shake flask and in bioreactor cultures, respectively. Fed-batch cultivation, with controlled pH, increased the biomass gradually in culture, reaching 28.5 g/l after 32 h cultivation. Beside the feasible use as a probiotic, the new strain also could be beneficial in the development of functional foods or novel food preservatives. To our knowledge, this is the first report of yeast with probiotic properties isolated from the Red Sea.     

Optimization of culture conditions for the production of rifamycin oxidase by Curvularia lunata

Maximum activity (8.9 IU/ml) of rifamycin oxidase in Curvularia lunata, grown in shake-flask culture at 28°C and pH 6.5, was after 96 h. Nearly all the glucose was used in 72 h. An initial culture pH of 6.5 and 28°C were optimum for the growth and enzyme production. Among various carbon and organic nitrogen sources, carboxymethylcellulose and peptone were the most effective for enzyme yield. The rate of enzyme production was enhanced when yeast extract was also added to the medium. The optimum medium for the production of rifamycin oxidase contained 10 g each of yeast extract, peptone and carboxymethylcellulose/l and 0.04% (NH₄)₂SO₄.The author is with the Biochemical Engineering Research and Process Development Centre, Institute of Microbial Technology, Post Box 1304, Sector 39-A, Chandigarh 160 014, India     

Culture Media Statistical Optimization for Biomass Production of a Ligninolytic Fungus for Future Rice Straw Degradation

The main objective of this study was to optimize a culture media for low scale biomass production of Pleurotus spp. Future applications of this optimization will be implemented for “in situ” rice straw degradation, increase soil nutrients availability, and lower residue and rice culture management costs. Soil samples were taken from different points in six important rice production cities in Colombia. For carbon and nitrogen source selection a factorial 4² design was carried out. The Plackett-Burman design permitted to detect carbon, nitrogen and inducer effects on fungus growth (response variable for all designs). This optimization was carried out by a Box-Behnken design. Finally a re-optimization assay for glucose concentration was performed by means of a One Factor design. Only 4/33 (12 %) isolates showed and important laccase or manganese peroxidase activity compared to Pleurotus ostreatus (HPB/P3). We obtained an increased biomass production in Pleurotus spp. (T1.1.) with glucose, followed by rice husk. Rice straw was considered an inducing agent for lignin degradation. Glucose was a significant component with positive effects, whereas Tween 80 and pH had negative effects. On the contrary, rice husk, yeast extract and CaCl₂ were not significant components for increase the biomass production. Final media composition consisted of glucose 25 g L^?1, yeast extract 5 g L^?1, Tween 80 0.38 % (v/v), Rice husk 10 g L^?1, CaCl₂ 1 g L^?1, and pH 4.88 ± 0.2. The Box-Behnken polynomial prediction resulted to be lower than the experimental validation of the model (6.59 vs. 6.91 Log₁₀ CFU ml^?1 respectively).     

A Thin‐Layer Liquid Culture Technique for the Growth of Helicobacter pylori

Background and Aims: Several attempts have been successful in liquid cultivation of Helicobaccter pylori. However, there is a need to improve the growth of H. pylori in liquid media in order to get affluent growth and a simple approach for examining bacterial properties. We introduce here a thin‐layer liquid culture technique for the growth of H. pylori. Methods: A thin‐layer liquid culture system was established by adding liquid media to a 90‐mm diameter Petri dish. Optimal conditions for bacterial growth were investigated and then viability, growth curve, and released proteins were examined. Results: Maximal growth of H. pylori was obtained by adding 3 mL of brucella broth supplemented with 10% horse to a Petri dish. H. pylori grew in both DMEM and RPMI‐1640 supplemented with 10% fetal bovine serum and 0.5% yeast extract. Serum‐free RPMI‐1640 supported the growth of H. pylori when supplemented with dimethyl‐β‐cyclodextrin (200 μg/mL) and 1% yeast extract. Under optimal growth, H. pylori grew exponentially for 28 hours, reaching a density of 3.4 OD₆₀₀ with a generation time of 3.3 hours. After 24 hours, cultures at a cell density of 1.0 OD₆₀₀ contained 1.3 ± 0.1 × 10⁹ CFU/mL. γ‐Glutamyl transpeptidase, nuclease, superoxide dismutase, and urease were not detected in culture supernatants at 24 hours in thin‐layer liquid culture, but were present at 48 hours, whereas alcohol dehydrogenase, alkylhydroperoxide reductase, catalase, and vacuolating cytotoxin were detected at 24 hours. Conclusions: Thin‐layer liquid culture technique is feasible, and can serve as a versatile liquid culture technique for investigating bacterial properties of H. pylori.     

Physiological characteristics of the trunk sap rot pathogen Fomitiporia sp. on the “Sanbu-sugi” cultivar of Cryptomeria japonica

An unidentified Fomitiporia sp. initially identified as Fomitiporia punctata, causes severe trunk sap rot on Cryptomeria japonica cultivar “Sanbu-sugi”. We investigated the physiological characteristics of the mycelia of the causal fungus (F2, F6, and F43), in comparison with F. punctata (Fp) as a reference, in eight different experiments. The three unidentified isolates showed similar tendencies in change in mycelial growth during incubation, optimal growth temperatures (25 °C), optimal pH range (pH 5–6), glucose to yeast extract ratio (45), utilizable carbon sources (amylose, CM-cellulose, and pectin), utilizable nitrogen sources (yeast extract and polypepton), and water potential (?1.7 Mpa).     

Catabolic Activities of Neisseria meningitidis: Utilization of Succinate

Two strains of Saccharomycopsis guttulata, JB-1 and JB-3, isolated from stomach contents of domestic rabbits, were grown under different gas phases, and their growth rates were compared. Strain JB-1 grew exponentially at a maximal growth rate under a continuous gas phase of 15% CO₂, 2% O₂ in nitrogen. High cell yields with low cell granulation were obtained. The growth rates were almost the same between oxygen concentrations of 0.25 and 20% at 15% CO₂. Poor growth and early cell granulation occurred in the absence of oxygen at 15% CO₂. Growth increased at 2% O₂ in direct proportion to the carbon dioxide concentration up to 10 to 15% CO₂. A very high carbon dioxide content (e.g. 98%) was somewhat inhibitory. Cell granulation always occurred during the maximal stationary phase in media at pH 4, but was relatively slight at pH 5.6 or higher. Strain JB-3 responded to various gas phases in a similar manner except that it grew slowly in the absence of oxygen at 15% CO₂ (pH 4). The effect of an optimal gas phase on the growth of strain JB-1 was examined in relation to other environmental conditions. In the presence of 15% CO₂, 2% O₂, this strain grew exponentially in yeast autolysate-Proteose Peptone-glucose medium at 37 C at pH 2, 4, and 5.6 at approximately the same rate; the growth rate was somewhat lower at pH 6.2. Under similar conditions, strain JB-1 grew at 30 C and pH 4 at one-sixth its maximal growth rate. Cell granulation was greatly reduced at this temperature. With adequate CO₂ strain JB-1 also grew at a reduced rate in a yeast autolysate medium previously reported not to support growth. Results indicate that continuous gassing with an optimal gas phase increases the growth rate to the extent that the growth rate surpasses the death rate by a significant margin; as a result, granulated cells can be avoided almost entirely in the log phase.     

Reactor-Scale Cultivation of the Hyperthermophilic Methanarchaeon Methanococcus jannaschii to High Cell Densities

For the hyperthermophilic and barophilic methanarchaeon Methanococcus jannaschii, we have developed a medium and protocols for reactor-scale cultivation that improved the final cell yield per liter from ~0.5 to ~7.5 g of packed wet cells (~1.8 g dry cell mass) under autotrophic growth conditions and to ~8.5 g of packed wet cells (~2 g dry cell mass) with yeast extract (2 g liter⁻¹) and tryptone (2 g liter⁻¹) as medium supplements. For growth in a sealed bottle it was necessary to add Se to the medium, and a level of 2 μM for added Se gave the highest final cell yield. In a reactor M. jannaschii grew without added Se in the medium; it is plausible that the cells received Se as a contaminant from the reactor vessel and the H₂S supply. But, for the optimal performance of a reactor culture, an addition of Se to a final concentration of 50 to 100 μM was needed. Also, cell growth in a reactor culture was inhibited at much higher Se concentrations. These observations and the data from previous work with methanogen cell extracts (B. C. McBride and R. S. Wolfe, Biochemistry 10:4312–4317, 1971) suggested that from a continuously sparged reactor culture Se was lost in the exhaust gas as volatile selenides, and this loss raised the apparent required level of and tolerance for Se. In spite of having a proteinaceous cell wall, M. jannaschii withstood an impeller tip speed of 235.5 cms⁻¹, which was optimal for achieving high cell density and also was the higher limit for the tolerated shear rate. The organism secreted one or more acidic compounds, which lowered pH in cultures without pH control; this secretion continued even after cessation of growth.     

Optimization of submerged culture conditions for exopolysaccharide production in <Emphasis Type="Italic">Sarcodon aspratus</Emphasis> (Berk) S.lto TG-3

The effect of medium components (carbon, nitrogen, and mineral sources) and environmental factors (initial pH and temperature) for mycelial growth and exopolysaccharide (EPS) production in Sarcodon aspratus(Berk) S.lto TG-3 was investigated. The optimal temperature (25°C) and initial pH (5.0) for the EPS production in shake flask cultures of S. aspratus were determined using the two-dimensional contour plot. The most suitable carbon, nitrogen, and mineral sources for EPS production were glucose, yeast extract, CaCl₂ and KH₂PO₄, respectively. Notably, the EPS production was significantly enhanced by supplementation of calcium ion. Subsequently, the optimum concentration of glucose (30gl^–1), yeast extract (15gl^–1), CaCl₂ (1.1gl^–1), and KH₂PO₄ (1.2gl^–1) were determined using the orthogonal matrix method. The effects of nutritional requirement on the mycelial growth of S.aspratuswere in regular sequence of glucose>KH₂PO₄>yeast extract>CaCl₂, and those on EPS production were in the order of glucose>yeast extract>CaCl₂>KH₂PO₄. Under the optimal culture conditions, the maximum EPS concentration in a 5-l stirred-tank reactor was 2.68gl^–1 after 4days of fermentation, which was 6-fold higher than that at a basal medium. The two-dimensional contour plot and orthogonal matrix method allowed us to find the relationship between environmental factors and nutritional requirement by determining optimal operating conditions for maximum EPS production in S.asparatus. The statistical experiments used in this work can be useful strategies for optimization of submerged culture processes for other mushrooms.     

pH effects on 10 Streptomyces spp. growth and sporulation depend on nutrients

AIMS: Streptomycetes are regarded to prefer neutral to alkaline environmental pH, although they commonly occur at remarkably variable pH and nutritional conditions. Therefore, the dependence of 10 Streptomyces spp. pH tolerance on nutrients was determined. METHODS AND RESULTS: Ten environmental Streptomyces spp. were grown and sporulated between pH 4.0 and 11.5, at the interval of 1.5, on starch-casein-KNO(3), tryptone-yeast extract-glucose, glycerol-arginine and tryptone-soy agars, and three their modifications. On media with starch and casein; glucose, tryptone and yeast extract; tryptone and soy peptone; and glycerol-arginine and yeast extract strains grew over a broad pH range between 4.0-5.5 and 10.0-11.5. On glycerol-arginine and on medium with Na-propionate, NH(4)NO(3) and yeast extract, streptomycetes grew optimally at pH 7.0 and above. The high organic load enabled the growth over a wide pH range. The sporulation pH ranges followed those for growth. CONCLUSIONS: The high organic load enabled the growth over a wide pH range. The strain-specific differences in sporulation were greater than those caused by pH. The best medium for sporulation contained glucose and tryptone with minerals of glycerol-arginine agar at pH 5.5. SIGNIFICANCE AND IMPACT OF THE STUDY: The growth pH ranges, pH ranges for the optimal growth, and sporulation were strongly dependent on nutrients.     

Optimization of bioconversion conditions for vitamin D3 to 25-hydroxyvitamin D using Pseudonocardia autotrophica CGMCC5098

The optimal culture conditions for bioconversion of vitamin D₃ to calcifediol (25(OH)D₃) were investigated by varying carbon and nitrogen sources, metal salt concentrations, initial pH, temperature, solvents, surfactants, and agitation speed. In the process of this microbial hydroxylation, the timing of the addition of vitamin D₃, which is dissolved in ethanol, is of critical importance. Besides, the concentration of ethanol in zymotic fluid is the key factor to get high conversion ratio of vitamin D₃. In particular, the optimal culture conditions were 1.5% glucose, 1.5% soybean cake meal, 0.5% yeast extract, 0.5% corn steep liquor, 0.3% CaCO₃, 0.1% NaCl, 0.2% KH₂PO₄, pH 7.2 at 27?°C and the timing of the addition of vitamin D₃ dissolved in 5% (v/v) ethanol was 48?h followed by the inoculation of seed culture broth. Under the optimized conditions, the conversion of vitamin D₃ (1?g/L) by Pseudonocardia autotrophica CGMCC5098 in 50?L fermenter resulted in about 61.31% bioconversion ratio (639?mg/L) of 25(OH)D₃ on the 5th day.     

Application of a simple yeast extract from spent brewer's yeast for growth and sporulation of Bacillus thuringiensis subsp. kurstaki: a Physiological Study

The suitability of using a simple brewer's yeast extract (BYE), prepared by autolysis of complete beer slurry, for growth and sporulation of Bacillus thuringiensis kurstaki was studied in baffled shake flasks. In a standard buffered medium with 2.5% (w/v) glucose and 1% (w/v) brewer's yeast extract, growth of B. t. kurstaki resulted in a low biomass production with considerable byproduct formation, including organic acids and a concomitant low medium pH, incomplete glucose utilization and marginal sporulation, whereas growth in the same medium with a commercial laboratory-grade yeast extract (Difco) resulted in a high biomass concentration, complete glucose utilization, relatively low levels of byproducts and complete sporulation (2.6 × 10⁹ spores/ml). When glucose was left out of the medium, however, growth parameters and sporulation were comparable for BYE and commercial yeast extract, but absolute biomass levels and spore counts were low. Iron was subsequently identified as a limiting factor in BYE. After addition of 3 mg iron sulphate/l, biomass formation in BYE-medium more than doubled, low byproduct formation was observed, and complete sporulation occurred (2.8 × 10⁹spores/ml). These data were slightly lower than those obtained in media with commercial yeast extract (3.6 × 10⁹spores/ml), which also benefited, but to a smaller extent, from addition of iron.     

Development of meridic and oligidic diets for rearing the aphid Myzus persicae

Meridic and oligidic diets suitable for the continuous culture of the aphid Myzus persicae were developed through modifications of a holidic diet. These included the addition of various amounts of crude nutrients and the replacement of defined nutrients by crude nutrients. The highest level of aphid growth (mean weights of 600 to 800 μg) was maintained (for 45 successive generations) on a meridic diet made by supplementing a holidic diet with 2.0% yeast extract (NBC).Continuous culture, at a level of growth (400 to 600 μg) comparable to that on the unsupplemented holidic diet (formulated with 34 defined nutrients), was supported by an oligidic diet containing only 10 weighed ingredients: 15 g sucrose, 2.5 g enzymatic casein hydrolysate (NBC), 2 g yeast extract, 123 mg MgSO₄·7H₂O, 100 mg ascorbic acid, 10 mg niacin, 5 mg Ca pantothenate, 2.5 mg pyridoxine, 2.5 mg thiamine, and appx. 1.5 gm K₂HPO₄·3H₂O (pH 6.8) per 100 ml of diet.Yeast extract at 2.0% provided adequate amounts of choline chloride, biotin, folic acid and inositol, but not of niacin, pantothenate, pyridoxine, and thiamine. Enzymatic casein hydrolyzate at 2.5% could replace the 20 defined amino acids of the holidic diet. Diets with both yeast extract and casein hydrolysate did not have to be supplemented with trace minerals (Cu, Fe, Mn and Zn). Yeast extract at 2.5% provided sufficient amounts of trace minerals, amino acids, and B-vitamins to sustain numerous successive generations, albeit at a low level of growth (200 to 300 μg). The simplicity and low cost of oligidic diets makes them attractive for aphid studies in which nutrition is not the primary consideration.