Mineral Nutrient Medium Research Articles

Isolation and Characterization of Brucella spp., Low-Density Polyethylene (LDPE) Plastic Degrading Bacteria in Al-Ahsa Region, Saudi Arabia

Plastic pollution is one of the most serious environmental issues, causing severe environmental damage. It is of vital importance to find an efficient and eco-friendly approach to biodegrading plastics. The aim of this study was to isolate and characterize different bacterial isolates from water samples in the Al-Ahsa region of Saudi Arabia. The ability to degrade low-density polyethylene (LDPE) plastic was evaluated using multiple approaches, including changes in the media pH values, weight loss, Fourier transform infrared (FTIR), and gas chromatography–mass spectrometry (GC–MS). The water samples were collected from plastic-contaminated sites in Al-Ahsa, and bacterial isolates were obtained using a mineral nutrient medium (MNM) enriched with LDPE as the only carbon and energy source. Two bacterial isolates (APCK5 and APCZ14) were obtained and they showed potential LDPE degradation, as evidenced by changes in media pH (from 7.0 ± 0.03 to 6.17 ± 0.05 and 6.22 ± 0.03), LDPE weight reduction (8.1 ± 0.63% and 18.85 ± 0.96%, respectively), and FTIR and GC–MS analyses. Based on 16S rRNA gene similarities, APCZ14 and APCK5 were determined to be most closely related to the genus Brucella. APCZ14 exhibited a 99.48% homology with Brucella cytisi, whereas APCK5 showed a 99.33% similarity level to Brucella tritici. In conclusion, both bacterial strains had high efficiency in plastic biodegradation and could be developed for wide use as an eco-friendly method to remove or reduce plastic pollutants from the environment.

Estimation of the Ability to Decompose Sodium Benzoate by a Bacterium Isolated from Biohumus Eicenia Fetida

The study presents growth kinetics of a BG28 bacterial strain isolated from vermicompost (generated with the use of Eisenia fetida worms). The strain was given a codename BG28. It was revealed that the isolate is capable of using high concentrations of sodium benzoate (up to 15 g/l) as a substrate. At the same time, the rate and division constants of a culture that grows at 5 g/l, 10 g/l, and 15 g/l do not differ. However, the mean and specific increment of BG28 at the end of the logarithmic growth phase is significantly higher in the variant with 5 g/l. It was testified, that with the shortest duration of the logarithmic growth phase on a medium with 5 g/l, the substrate loss constant is higher than in other variants. The difference in the kinetic parameters of the culture at 5 g/l and 10 g/l sodium benzoate is insignificant. With an increase of the substrate concentration to 15 g/l, the duration of the logarithmic growth phase increased significantly, but the sodium benzoate decrease constant was found to be the lowest. During the study of the individual properties of BG28, it was revealed that the strain is capable of growing on benzoic acid. On this basis, it can be assumed that the culture contributes to the degradation of plant residues during vermicomposting. Besides, the isolate grows on a mineral nutrient medium with polyethylene glycol 6000 and liquid paraffin. In the process of the individual properties estimation, it was revealed that the strain is capable of local suppression of the Alternaria brassicicola VKM F-1864 mold growth when co-cultivated on agar nutrient medium.

ISOLATION OF METHANOTROPHIC BACTERIA FROM NATURAL BIOCENOSES AND SELECTION OF NUTRIENT MEDIA OPTIMAL FOR CULTIVATION IN LABORATORY CONDITIONS

Background. One of the most pressing problems in the world is the production of food protein. The global protein deficit is estimated at 30 million tons per year, for the Russian Federation it is estimated at 2-2.5 million tons of protein per year.
 The problem of protein deficit can be partially solved with the help of methanotrophic bacteria. Under optimal conditions, methanotrophic bacteria are able to oxidise actively natural gas – methane and increase their biomass, rich in valuable protein, vitamins and other biologically active substances. The feed product from methanotrophic bacteria is comparable to fish meal and soybean meal, the concentration of pure protein in it is more than 80%.
 Purpose. Isolation of methanotrophic bacteria from natural biocenoses and their cultivation on various nutrient media in laboratory conditions.
 Materials and Methods. The study was conducted from 2019 to 2022 in the microbiological laboratory of the Center for Technological Excellence “Advanced Chemical and Biotechnology” of the Tolstoy Tula State Pedagogical University. The object of the study was methanotrophic bacteria isolated from various natural and artificial ecosystems, collection strains of Methylococcus capsulatus B-2990 and Methylomonas methanica B-2110. To isolate methanotrophic bacteria, the method of seeding a accumulative culture on a solid agiarized sterile nutrient medium in Petri dishes was used. For the cultivation of methanotrophs, nutrient media of various compositions containing all the necessary macro- and microelements for the normal growth of bacterial colonies were used.
 Results. Colonies of methanotrophic bacteria were found in one sample of bottom sediments taken from the sphagnum swamp of the village of Kochaki in the Tula region and in samples from a methane reactor. As a result of comparison of nutrient media for isolation and cultivation of methanotrophs, it was found that the most suitable medium for isolation of methanotrophic bacteria is the standard nitrate mineral medium NMS. For the cultivation of methanotrophic bacteria, the best media were: the nutrient medium with the addition of anaerobic sludge, the ammonium mineral nutrient medium (AMS), and AMS with addition of methanol, the nutrient medium No.221 with addition of methanol.
 Conclusions. The use of various nutrient media for the cultivation of methanotrophic bacteria makes it possible to assess the effect of various organic substances on the growth and development of bacterial colonies. The study of various natural and artificial ecosystems makes it possible to expand taxonomic knowledge about this group of microorganisms, as well as to increase the potential of using methanotrophs in solving various problems of ecology and biotechnology.

Bioremediation Treatment of Polyaromatic Hydrocarbons for Environmental Sustainability

Polycyclic aromatic hydrocarbons (PAHs) distributed in air and soil are harmful because of their carcinogenicity, mutagenicity, and teratogenicity. Biodegradation is an environmentally friendly and economical approach to control these types of contaminants and has become an essential method for remediating environments contaminated with petroleum hydrocarbons. The bacteria are isolated and identified using a mineral nutrient medium containing PAHs as the sole source of carbon and energy and biochemical differential tests. Thus, this study focuses on some bacteria and fungi that degrade oil and hydrocarbons. This study provides a comprehensive, up-to-date, and efficient overview of petroleum hydrocarbon contaminant bioremediation considering hydrocarbon modification by microorganisms, emphasizing the new knowledge gained in recent years. The study shows that petroleum hydrocarbon contaminants are acceptably biodegradable by some microorganisms, and their removal by this method is cost-effective. Moreover, microbial biodegradation of petroleum hydrocarbon contaminants utilizes the enzymatic catalytic activities of microorganisms and increases the degradation of pollutants several times compared to conventional methods. Biological treatment is carried out in two ways: microbial stimulation and microbial propagation. In the first method, the growth of indigenous microorganisms in the area increases, and the pollution is eliminated. In the second method, on the other hand, there are no effective microorganisms in the area, so these microorganisms are added to the environment.

The effect of Anavidin on <i> Rhodococcus qingshengii</i> VKM Ac-2784D depending on the carbon source in the cultivation medium

Background. Microorganisms have significant plasticity, therefore, the effectiveness of the use of disinfectants is due to the conditions of their use. This is because microorganisms, depending on their habitat, may have different resistance to the same active substance.The aim. To study the effect of Anavidin-Complit on the growth and biofilm formation of Rhodococcus qingshengii VKM Ac-2784D, depending on the carbon source in the cultivation medium.Materials and methods. R. qingshengii VK MAc-2784D was used in the work, the studies were carried out on a mineral nutrient medium 8E, into which 0.5 % glucose, inositol or naphthalene was added as a carbon source. Anavidin was used at a final concentration of 0.08, 0.04, 0.02, 0.01 and 0.005 %. Growth and biofilm formation were evaluated by standard microbiological methods.Results. The disinfecting effect of Anavidin-Complit on the growth of the planktonic form of R. qingshengii VKM Ac-2784D depends on the carbon source. If in a starvation cultivation medium, all concentrations of Anavidin-Complit had an adverse effect on bacteria throughout the experiment, then in the presence of glucose, the adverse effect of low concentrations of Anavidin-Complit decreased by the end of the experiment. In the medium with naphthalene, on the contrary, on the first or second day of cultivation, low concentrations of Anavidin-Complit had a stimulating effect. Anavidin-Complit, depending on the concentration, suppressed the formation of a biofilm on all cultivation media. Microscopy of the biofilm in some cases revealed dense rounded formations consisting of several layers of cells.Conclusion. Thus, in order to increase the effectiveness of disinfectants, a deeper study of the physiological response of microorganisms is necessary, taking into account their living conditions.

Pyrite Biooxidation by Acidophilic Archaea AcidiplasmaSp. MBA-1 Under Varied Conditions

The goal of this research was to study pyrite (FeS2 ) bioleaching by a strain of the genus Acidiplasma under different conditions (temperature, pH) to evaluate the potential role of Acidiplasma representatives in biooxidation of this sulfide mineral. To compare the role of Acidiplasma archaea in pyrite biooxidation with other acidophilic microorganisms, the experiments were also performed with representatives of othergroups of microorganisms predominant in biohydrometallurgical processes.Pure and mixed cultures of moderately thermophilic acidophilic microorganisms, including strains Acidithiobacillus caldus MBC-1, Sulfobacillusthermosulfidooxidans VKMV 1269T and Acidiplasmasp. MBA-1, were used. The experiments were carried out in flasks with 100 mL of mineral nutrient medium supplemented with 0.02% yeast extract and 1 g of pyrite on a rotary shaker for 20 days. Bioleaching was performed at 45, 55, and 60∘С. The results demonstrated that the representatives of the genus Acidiplasmaprovided a comparatively higher rate of pyrite bioleaching at high temperatures (55 and 60∘C) and low pH of the medium (1.0). Thus, according to the results, strains of thegenus Acidiplasma may provide a high rate of pyrite bioleaching at low levels ofpH. Therefore, the results suggest that archaea of the genus Acidiplasma may be promising microorganisms to improve bioleaching processes with an increase in the operational temperature, which is usually maintained at 40–45∘C in industrial-scale reactors.
 Keywords: biomining, bioleaching, acidophilic microorganisms, sulfide minerals, pyrite

Morphological diversity of benthic cyanobacterial assemblages in meltwater ponds along environmental gradients in the McMurdo Sound region, Antarctica.

Benthic cyanobacterial assemblages from ponds distributed along inland-coastal gradients in the McMurdo Sound region were studied during the 2011/12 Antarctic summer season. Twenty-five ponds were sampled in four distinct geographic locations, including the Lower and Upper Wright Valleys, Ross Island and the McMurdo Ice Shelf. For morphological identification, benthic mat samples were thawed and a subsample was directly observed by light microscopy. Remaining sample material was stored in 50 ml sterile polycarbonate bottles containing the mineral nutrient medium MLA for future studies, maintained at a temperature of 21°C. Ten morphological criteria were used to describe the morphotypes (trichome shape, number of trichomes in sheath, presence or absence of terminal attenuation of trichome, calyptra on mature apical cell, shape of apical cell, presence or absence of constrictions at transverse walls, granules, branching, range in width of trichomes and range of cell length) with reference to available identification literature. All morphospecies were documented using photomicrography. In total, 29 morphospecies were described, four assigned to the order Chroococcales, three to Nostocales and 22 to Oscillatoriales. The four geographic locations had similar taxonomic richness, sharing many morphospecies. However, each also contained distinct floristic elements that were rare or absent from the others.

Reduced major minerals and increased minor nutrients improve micropropagation in three apple cultivars

Mineral nutrient medium requirements for propagation of in vitro shoots of apple (Malus domestica Borkh) ‘Golden Delicious’, ‘Maksat’, and ‘Voskhod’ were studied using response surface methodology (RSM). The mineral nutritional factors evaluated were based on Murashige and Skoog (MS) mineral nutrients (NH4NO3, KNO3, CaCl2, KH2PO4, MgSO4, and minor nutrients), with concentrations ranging from 0.5 to 3.0× the MS concentrations. Nine plant growth qualities were evaluated. The most significant factors were NH4NO3 at 0.5 to 1.0× MS, and minor nutrients at 2.0× MS. Most of the other factors were optimal at 0.5×. The quality rating was highest when minor nutrients were 2.0× MS, and most other nutrients were standard concentrations or lower. Increased KH2PO4 and minor nutrients were the most significant for improved multiplication, and higher KNO3 for shoot length. Optimized media were developed for each cultivar based on these models. The cultivars were grown on the three individual optimized media, a general medium based on the three optimizations, and MS. The optimized medium for each cultivar was significantly better for shoot quality and shoot length of each cultivar than MS, but the generalized medium of minors at 2.0× and NH4NO3, CaCl2, and MgSO4 at 0.5× MS, was significantly better for two of the three cultivars and not significantly different for the third. The next step to develop a final optimized medium will require the evaluation of the minor nutrients, determination of optimal concentrations of each, and screening a wide range of Malus germplasm on the finalized medium.

ANAMMOX BACTERIA DETERMINATION IN THE PHARMACEUTICAL PRODUCTION WASTEWATER

Anammox bacteria are found in sewage treatment systems, as well as in the other ecological niches, where there are anaerobic conditions. The aim of the study was to establish the ANAMMOX bacteria (Anaerobic AMMonium OXidation) presence and their systematic affiliation in active sludge samples. Methods. The ammonium, nitrite and nitrate concentration determination in the samples was obtained using spectrophotometric reactions. The ANAMMOX process presence was determined by the active sludge incubation method with mineral nutrient medium under anaerobic conditions. The anammox bacteria presence and genus affiliation were determined by FISH (fluorescence hybridization in situ) technique using specific tagged primers: the universal Tamra-Amx-0368, and also FamAmx-0820 and Fam-Kst-1 275. Results. For the anammox bacteria synthetic nutrient medium preparation there were determined the ammonium and nitrite ions concentration in the experimental test. The nutrient mineral medium was analyzed for the residual ammonium and nitrite ions concentration after cultivation. For further visual examination of the ANAMMOX bacteria, FISH reaction and the samples microscopy there were performed. Three tagged primers were used in the reaction: the universal Tamra-Amx-0368, and also Fam-Amx-0820 and FamKst-1 275. Conclusions.The decrease of the concentration of ammonium ions by 0,0395 g / l and ions nitrites at 0.0179 g / l in a synthetic nutrient medium in anaerobic conditions with gas release indicates the presence of microorganisms responsible for the ANAMMOX process. The hybridization results indicated Can. Brocadia and Can. Kuenenia presence in the sludge and water sample, in the range of 8 to 10 microcolonial units per 50 μl, as well as Kuenenia stuttgartiensis, but in smaller number, 3 to 4, of microcolonial units.

Biodegradation of chlorpyrifos and 3,5,6-trichloro-2-pyridinol by the epiphytic yeasts Rhodotorula glutinis and Rhodotorula rubra.

The possible involvement of the epiphytic yeasts Rhodotorula glutinis and Rhodotorula rubra in the biodegradation of the insecticide chlorpyrifos and its metabolite 3,5,6-trichloro-2-pyridinol (TCP), in pure cultures and in plant surfaces (tomato fruits) was investigated. Higher biodegradation rates were observed as the concentration of chlorpyrifos and the inoculum of the microorganisms were increased, while the yeasts proved to be more active at 25 and 15 °C. The presence of glucose in the mineral nutrient medium, as an extra source of carbon, delayed the biodegradation by Rhodotorula glutinis, while Rhodotorula rubra proved to be more active. The detection and quantification of the parent compound and TCP was successfully achieved using a LC/MS/MS chromatographic system. The in vitro enzymatic assays applied suggested that esterases may be involved in the biodegradation of chlorpyrifos, a fact that was further enhanced after the addition of the synergists triphenyl phosphate, diethyl maleate and piperonyl butoxide in the biodegradation trials. The decrease of chlorpyrifos residues on tomato fruits confirmed the corresponding on pure cultures, resulting in the suggestion that the yeasts R. glutinis and R. rubra can possibly be used successfully for the removal or detoxification of chlorpyrifos residues on tomatoes.

Involutin is an Fe3+ reductant secreted by the ectomycorrhizal fungus Paxillus involutus during Fenton-based decomposition of organic matter.

Ectomycorrhizal fungi play a key role in mobilizing nutrients embedded in recalcitrant organic matter complexes, thereby increasing nutrient accessibility to the host plant. Recent studies have shown that during the assimilation of nutrients, the ectomycorrhizal fungus Paxillus involutus decomposes organic matter using an oxidative mechanism involving Fenton chemistry (Fe2+ + H2O2 + H+ → Fe3+ + ˙OH + H2O), similar to that of brown rot wood-decaying fungi. In such fungi, secreted metabolites are one of the components that drive one-electron reductions of Fe3+ and O2, generating Fenton chemistry reagents. Here we investigated whether such a mechanism is also implemented by P. involutus during organic matter decomposition. Activity-guided purification was performed to isolate the Fe3+-reducing principle secreted by P. involutus during growth on a maize compost extract. The Fe3+-reducing activity correlated with the presence of one compound. Mass spectrometry and nuclear magnetic resonance (NMR) identified this compound as the diarylcyclopentenone involutin. A major part of the involutin produced by P. involutus during organic matter decomposition was secreted into the medium, and the metabolite was not detected when the fungus was grown on a mineral nutrient medium. We also demonstrated that in the presence of H2O2, involutin has the capacity to drive an in vitro Fenton reaction via Fe3+ reduction. Our results show that the mechanism for the reduction of Fe3+ and the generation of hydroxyl radicals via Fenton chemistry by ectomycorrhizal fungi during organic matter decomposition is similar to that employed by the evolutionarily related brown rot saprotrophs during wood decay.

Changes in the composition and properties of humic acids under the influence of microorganisms

By gel filtration on Sephadex G-50 and G-75, we investigated the changes in the composition and ratio of the molecular fractions of humic acids under the influence of native soil microbial complexes. The highest degree of decomposition of the initial humic acid was observed when ammonium nitrate was used as a source of additional energy in the mineral nutrient medium without a yeast extract. The appearance of a low molecular fraction of organic substances on chromatograms may be associated with the synthesis by bacteria of simple organic substances on the medium with humic acids as a single source of carbon.

Growth peculiarities of hydrocarbon-oxidizing rhodococcus and pseudomonads dissociates in mono- and mixed cultures

Growth of R-, S-, and M-dissociates of Rhodococcus rubropertinctus in mixed culture with R-, S-, and M-dissociates of Rhodococcus aeruginosa in comparison with rhodococcus monoculture cultivated on mineral nutrient medium with hexadecane has been studied. The amount of cells in the stationary growth phase has increased 10-15 times in comparison with the monoculture, and pseudomonads which dominated in population, in associations of M-dissociate of R. rubropertinctus with any dissociate of R. aeruginosa or two S-dissociates in the studied bacterial species. The emulsifying ability of the cells (maximal in R-dissociates), the synthesis of surface active compounds in pseudomonads, which is maximal in M-dissociate had the main influence on the growth of rhodococci on the nutrient medium with hydrocarbons.

Accelerated biodegradation of n-alkanes in aqueous solution by the addition of fermented whey

Abstract The effect of fermented whey on the aerobic degradation of n -alkanes by a microbial consortium was investigated in an aqueous system. Microbial degradation of 100 mg n -alkanes l −1 (C 12 , C 14 , C 16 and C 18 ) in mineral nutrient medium was assessed by measuring the decrease in n -alkanes, production of CO 2 and increase in biomass. The addition of fermented whey at a concentration of 5 mg dry weight l −1 to a nutrient medium receiving a small-sized inoculum (10 3.4 CFU ml −1 ) shortened the lag phase from 8 to 3 days, but the degradation rate during the degradation phase was not enhanced. The shortened lag phase at low initial concentration of microorganisms indicates that the fermented whey stimulates growth in the initial phase, without reducing the consortium's capacity for n -alkane degradation.

Mineral nutrition and adventitious rooting in microcuttings of Eucalyptus globulus

We characterized the adventitious rooting response of Eucalyptus globulus Labill. to various concentrations of calcium, nitrogen, phosphorus, iron, manganese, zinc, boron and copper. The parameters analyzed were percent rooting, root number, root length and mean rooting time. Root number and root length were significantly affected by mineral nutrition, whereas mean rooting time and rooting percentage seemed to be closely related to auxin availability. Root number was affected by calcium, nitrogen source and zinc, whereas root length was influenced by concentrations of phosphorus, iron and manganese, and by nitrogen source. Based on these results, we evaluated various combinations of several concentrations of these minerals in each rooting phase. Cuttings that were rooted in an optimized mineral nutrient medium and acclimatized to ex-vitro conditions for two months showed significantly higher survival after transplanting and drought stress than cuttings rooted in basal medium and treated in the same way.

Selection of Microorganisms Capable of Degrading Petroleum and Its Products at Low Temperatures

Of 150 cultures capable of degrading petroleum at +6°C, 40 strains growing in a liquid mineral nutrient medium containing petroleum (2%) as the sole source of carbon were selected. Of them, 13 cultures displaying a petroleum degradation rate exceeding 25% were selected. Abilities of these cultures and their associations to utilize fuel oil and its components—oils and benzene resins—were studied. A culture exhibiting degradation rates of fuel oil, its oils, benzene resins, and petroleum amounting to 17, 26, 10, and 51%, respectively, was selected. This culture can be used for cleanup of petroleum pollution under cold climatic conditions.

Leaf mineral nutrient concentrations or media pH affect Georgia Jet sweetpotato transplant number, length, and weight1

Abstract The results of four experiments were combined to determine the relationships between leaf mineral nutrients or media pH and sweetpotato transplant production. The relative number of transplants and the relative mean transplant lengths or weights were determined by comparing the values obtained with unamended aged pine sawdust, a traditional medium. These values were regressed against leaf mineral concentrations and media pH. There was no relationship between relative transplant production and leaf nitrogen (N), potassium (K), or manganese (Mn) concentrations. Compared to sufficiency ranges for nearly mature sweetpotatoes, concentrations of N and K were low and Mn was sufficient. An upper value of 1210 mg/L leaf iron (Fe) was obtained for relative mean transplant weight, but concentrations of this mineral were not associated with relative transplant numbers or relative mean transplant lengths. Leaf calcium (Ca) and magnesium (Mg) concentrations were related to all three transplant characteristics ...

Effects of zinc on the structure and growth dynamics of a natural freshwater phytoplankton assemblage reared in the laboratory

The response of a natural phytoplankton assemblage to different concentrations of Zn 2+ was evaluated by means of a static laboratory bioassay. Aliquots of surface water, taken in autumn from a non-polluted point of the Reconquista River (Buenos Aires, Argentia), were incubated in mineral nutrient media containing 2·5, 10 or 25 mg litre −1 of Zn 2+ (as zinc chloride). The comparative structure and dynamics of the communities were followed through periodic physico-chemical and biological analyses of samples taken during 24 days of incubation. Under the experimental conditions of the bioassays, the existence of several Zn 2+ tolerant algal species was shown: the most important of them were Chlorella vulgaris Beij. (Chlorophyceae, Chlorococcales), Nitzschia palea (Kütz.) Smith and Gomphonema parvulum (Kütz.) Kütz. (Bacillariophyceae). It was also demonstrated that the algal responses to Zn 2+ were selectively concentration dependent: at 2·5 and 10 mg litre −1 a stimulatory effect was observed in the diatoms; at 25 mg litre −1, diatom toxicity occurred. In contrast, Chlorophyceae growth was stimulated at the maximal Zn level. In general, the diversity, richness and equitability of the community were adversely affected by Zn in a concentration-dependent fashion.

Somatic embryogenesis and plantlet regeneration in the genus Secale

A tissue culture of five wild species of the Secale genus, i.e., S. africanum (Stapf.), S. ancestrale (Zhuk.), S. kuprianovii (Grossh), S. segetale (Rosher.), and S. vavilovii (Grossh), from immature embryos of sizes (stages) varying between 1.0 mm to 3.0mm, cultured on MS (1962) mineral nutrient medium supplemented with 0.62 mg/1-5.0 mg/1 of 2,4-D, was established. Initially various types of callus were observed and a correlation between genotype, size of explant and 2,4-D concentration was found. The best embryogenic response was observed when explants were smaller than 1.0 mm. Induction of somatic embryogenesis of 2.0 mm-3.0 mm explants required a higher concentration of 2,4-D. Most embryoids were formed in the presence of 5.0 mg/l of 2,4-D. Secale africanum and S. kuprianovii appeared to have the highest embryogenic capacity among the five investigated species. For embryoids germination to plantlets the MS medium supplemented with GA3 and cytokinins was used. Ultimately, out of the 932 regenerants obtained 364 originated from somatic embryogenesis.

High-density culture of marine microalgae — Promising items for mariculture: II. Determination of optimal light regime for Chlorella sp.f. marina under high-density culture conditions

Experiments to determine the optimal light regime for cultivating marine Chlorella were carried out in cultivators of two types: a 2-1 bubbling cultivator with a 15-mm-thick suspension layer, and a circulation cultivator with a 2-mm-thick suspension layer. The batch and continuous cultures were grown in a mineral nutrient medium with the content of nutrients maintained at a stable level of 300 mg N/l, 90 mg P/l, 30 mg Mg/l and 30 mg S/l, at the temperature of 33°C and pH 7.0–7.5. The light sources used were RHL-1000 W and RNaH-400 W lamps as well as sunlight. The radiant energy from different light sources was equalized to provide 2400 W·h −1 per day photosynthetically active radiation (PAR) in the laboratory and 2000–3000 W·h −1 per day PAR in the open air. Higher yields were obtained with natural illumination and with RNaH-400 W lamps. The effect of light intensity on yield was studied with light intensities of 75, 150, 250 and 300 W/m 2 PAR. 250 W/m 2 PAR proved to be optimal at a dry biomass concentration of no less than 0.5 g/l. At this light intensity the maximal daily yield obtained per 1 m 2 of the illuminated surface was 50 g of dry biomass (15-mm-thick layer), the maximal growth rate was 0.1 h −1 and the efficiency of radiant energy utilization was 4%. Results are also presented of growing marine Chlorella under conditions where growth is not limited by light availability.