The effect of selenium supplementation in inorganic and organic form was investigated in three fi... more The effect of selenium supplementation in inorganic and organic form was investigated in three five-member groups of ewes and their lambs in the course of 7 months. The basal feed ration contained 55 µg Se, ewes of experimental group E1 received a supplement of 180 µg Se in sodium selenite, and ewes of experimental group E2 were applied a supplement
The freshwater microalga Chlorella vulgaris was grown heterotrophically in fed-batch 50-600-L fer... more The freshwater microalga Chlorella vulgaris was grown heterotrophically in fed-batch 50-600-L fermenters at 36°C, on aerated and mixed nutrient solution with urea as a nitrogen and glucose as a carbon and energy source. Cell density increased from the initial value 6.25 to 117.18 g DW L −1 in 32 h in the fermenter 50 L at a mean growth rate 3.52 g DW L −1 h −1 . The DW increase in the fermenter 200 L was from 7.25 to 94.82 g DW L −1 in 26.5 h at a mean growth rate 3.37 g DW L −1 h −1 . Mean specific growth rate μ was about 0.1 h −1 in the both fermenters, if nutrients and oxygen were adequately supplied. The DW increase in the fermenter 600 L was from 0.8 to 81.6 g DW L −1 in 66.5 h at a mean growth rate 1.22 g DW L −1 h −1 and μ=0.07 h −1 . A limitation of the cell growth rate in 600 L fermenter caused by a low dissolved oxygen concentration above cell densities higher than 10 g DW L −1 ) occurred. Specific growth rate decreased approximately linearly with increasing glucose concentration (25-80 g glucose L −1 ) at the beginning of cultivation and decreased with the time of cultivation. The cell yield was 0.55-0.69 g DW (g glucose) −1 . The content of proteins, β-carotene, and chlorophylls in the cells steadily increased and starch content decreased, by keeping aerated and mixed culture another 12 h in fermenter after the cell growth was stopped due to glucose deficiency.
Flue gas generated by combustion of natural gas in a boiler was used for outdoor cultivation of C... more Flue gas generated by combustion of natural gas in a boiler was used for outdoor cultivation of Chlorella sp. in a 55 m 2 culture area photobioreactor. A 6 mm thick layer of algal suspension continuously running down the inclined lanes of the bioreactor at 50 cm s −1 was exposed to sunlight. Flue gas containing 6-8% by volume of CO 2 substituted for more costly pure CO 2 as a source of carbon for autotrophic growth of algae. The degree of CO 2 mitigation (flue gas decarbonization) in the algal suspension was 10-50% and decreased with increasing flue gas injection rate into the culture. A dissolved CO 2 partial pressure (pCO 2 ) higher than 0.1 kPa was maintained in the suspension at the end of the 50 m long culture area in order to prevent limitation of algal growth by CO 2 . NO X and CO gases (up to 45 mg m −3 NO X and 3 mg m −3 CO in flue gas) had no negative influence on the growth of the alga. On summer days the following daily net productivities of algae [g (dry weight) m −2 ] were attained in comparative parallel cultures: flue gas = 19.4-22.8; pure CO 2 = 19.1-22.6. Net utilization (η) of the photosynthetically active radiant (PAR) energy was: flue gas = 5.58-6.94%; pure CO 2 = 5.49-6.88%. The mass balance of CO 2 obtained for the flue gas stream and for the algal suspension was included in a mathematical model, which permitted the calculation of optimum flue gas injection rate into the photobioreactor, dependent on the time course of irradiance and culture temperature. It was estimated that about 50% of flue gas decarbonization can be attained in the photobioreactor and 4.4 kg of CO 2 is needed for production of 1 kg (dry weight) algal biomass. A scheme of a combined process of farm unit size is proposed; this includes anaerobic digestion of organic agricultural wastes, production and combustion of biogas, and utilization of flue gas for production of microalgal biomass, which could be used in animal feeds. A preliminary quantitative assessment of the microalgae production is presented.
Background: Selenium is a trace element performing important biological functions in many organis... more Background: Selenium is a trace element performing important biological functions in many organisms including humans. It usually affects organisms in a strictly dosage-dependent manner being essential at low and toxic at higher concentrations. The impact of selenium on mammalian and land plant cells has been quite extensively studied. Information about algal cells is rare despite of the fact that they could produce selenium enriched biomass for biotechnology purposes.
The freshwater alga Chlorella, a highly productive source of starch, might substitute for starch-... more The freshwater alga Chlorella, a highly productive source of starch, might substitute for starch-rich terrestrial plants in bioethanol production. The cultivation conditions necessary for maximizing starch content in Chlorella biomass, generated in outdoor scale-up solar photobioreactors, are described. The most important factor that can affect the rate of starch synthesis, and its accumulation, is mean illumination resulting from a combination of biomass concentration and incident light intensity. While 8.5% DW of starch was attained at a mean light intensity of 215 mmol/(m 2 s 1 ), 40% of DW was synthesized at a mean light intensity 330 mmol/(m 2 s 1 ). Another important factor is the phase of the cell cycle. The content of starch was highest (45% of DW) prior to cell division, but during the course of division, its cellular level rapidly decreased to about 13% of DW in cells grown in light, or to about 4% in those kept in the dark during the division phase. To produce biomass with high starch content, it is necessary to suppress cell division events, but not to disturb synthesis of starch in the chloroplast. The addition of cycloheximide (1 mg/L), a specific inhibitor of cytoplasmic protein synthesis, and the effect of element limitation (nitrogen, sulfur, phosphorus) were tested. The majority of the experiments were carried out in laboratory-scale photobioreactors, where culture treatments increased starch content to up to about 60% of DW in the case of cycloheximide inhibition or sulfur limitation. When the cells were limited by phosphorus or nitrogen supply, the cellular starch content increased to 55% or 38% of DW, respectively, however, after about 20 h, growth of the cultures stopped producing starch, and the content of starch again decreased. Sulfur limited and cycloheximide-treated cells maintained a high content of starch (60% of DW) for up to 2 days. Sulfur limitation, the most appropriate treatment for scaled-up culture of starchenriched biomass, was carried out in an outdoor pilot-scale experiment. After 120 h of growth in complete mineral medium, during which time the starch content reached around 18% of DW, sulfur limitation increased the starch content to 50% of DW.
A flue gas originating from a municipal waste incinerator was used as a source of CO 2 for the cu... more A flue gas originating from a municipal waste incinerator was used as a source of CO 2 for the cultivation of the microalga Chlorella vulgaris, in order to decrease the biomass production costs and to bioremediate CO 2 simultaneously. The utilization of the flue gas containing 10-13% (v/v) CO 2 and 8-10% (v/v) O 2 for the photobioreactor agitation and CO 2 supply was proven to be convenient. The growth rate of algal cultures on the flue gas was even higher when compared with the control culture supplied by a mixture of pure CO 2 and air (11% (v/v) CO 2 ). Correspondingly, the CO 2 fixation rate was also higher when using the flue gas (4.4 g CO 2 l −1 24 h −1 ) than using the control gas (3.0 g CO 2 l −1 24 h −1 ). The toxicological analysis of the biomass produced using untreated flue gas showed only a slight excess of mercury while all the other compounds (other heavy metals, polycyclic aromatic hydrocarbons, polychlorinated dibenzodioxins and dibenzofurans, and polychlorinated biphenyls) were below the limits required by the European Union foodstuff legislation. Fortunately, extending the flue gas treatment prior to the cultivation unit by a simple granulated activated carbon column led to an efficient absorption of gaseous mercury and to the algal biomass composition compliant with all the foodstuff legislation requirements.
Feedstuffs are routinely supplemented with various selenium sources, where organic forms of Se ar... more Feedstuffs are routinely supplemented with various selenium sources, where organic forms of Se are more bio-available and less toxic than the inorganic forms (selenites, selenates). When the algae are exposed to environmental Se in the form of selenite, they are able as other microorganisms to incorporate the element to different levels, depending on the algae species. Technology of heterotrophic fed-batch cultivation of the microalga Chlorella enriched by organically bound Se was developed, where the cultivation proceeds in fermentors on aerated and mixed nutrient solution with urea as a nitrogen and glucose as a carbon and energy source. High volumetric productivity and high cell concentrations (about 70-100 g Chlorella dry mass l −1 ) can be attained if nutrients and oxygen are adequately supplied. Addition of a small quantity of a new selenoprotein source-spray-dried Se-Chlorella biomass to the diet of farm animals had better effects on specific physiological and physical parameters of animals than selenite salt and was comparable with Se yeast added to the diet. This review introduces the importance of selenium for humans and animals, methods of Se determination, heterotrophic production of selenium-enriched Chlorella biomass in a fed-batch culture regime on organic carbon, and use of the biomass in animal nutrition.
Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2009
Background: Selenium is a trace element performing important biological functions in many organis... more Background: Selenium is a trace element performing important biological functions in many organisms including humans. It usually affects organisms in a strictly dosage-dependent manner being essential at low and toxic at higher concentrations. The impact of selenium on mammalian and land plant cells has been quite extensively studied. Information about algal cells is rare despite of the fact that they could produce selenium enriched biomass for biotechnology purposes.
The effect of selenium supplementation in inorganic and organic form was investigated in three fi... more The effect of selenium supplementation in inorganic and organic form was investigated in three five-member groups of ewes and their lambs in the course of 7 months. The basal feed ration contained 55 µg Se, ewes of experimental group E1 received a supplement of 180 µg Se in sodium selenite, and ewes of experimental group E2 were applied a supplement
The freshwater microalga Chlorella vulgaris was grown heterotrophically in fed-batch 50-600-L fer... more The freshwater microalga Chlorella vulgaris was grown heterotrophically in fed-batch 50-600-L fermenters at 36°C, on aerated and mixed nutrient solution with urea as a nitrogen and glucose as a carbon and energy source. Cell density increased from the initial value 6.25 to 117.18 g DW L −1 in 32 h in the fermenter 50 L at a mean growth rate 3.52 g DW L −1 h −1 . The DW increase in the fermenter 200 L was from 7.25 to 94.82 g DW L −1 in 26.5 h at a mean growth rate 3.37 g DW L −1 h −1 . Mean specific growth rate μ was about 0.1 h −1 in the both fermenters, if nutrients and oxygen were adequately supplied. The DW increase in the fermenter 600 L was from 0.8 to 81.6 g DW L −1 in 66.5 h at a mean growth rate 1.22 g DW L −1 h −1 and μ=0.07 h −1 . A limitation of the cell growth rate in 600 L fermenter caused by a low dissolved oxygen concentration above cell densities higher than 10 g DW L −1 ) occurred. Specific growth rate decreased approximately linearly with increasing glucose concentration (25-80 g glucose L −1 ) at the beginning of cultivation and decreased with the time of cultivation. The cell yield was 0.55-0.69 g DW (g glucose) −1 . The content of proteins, β-carotene, and chlorophylls in the cells steadily increased and starch content decreased, by keeping aerated and mixed culture another 12 h in fermenter after the cell growth was stopped due to glucose deficiency.
Flue gas generated by combustion of natural gas in a boiler was used for outdoor cultivation of C... more Flue gas generated by combustion of natural gas in a boiler was used for outdoor cultivation of Chlorella sp. in a 55 m 2 culture area photobioreactor. A 6 mm thick layer of algal suspension continuously running down the inclined lanes of the bioreactor at 50 cm s −1 was exposed to sunlight. Flue gas containing 6-8% by volume of CO 2 substituted for more costly pure CO 2 as a source of carbon for autotrophic growth of algae. The degree of CO 2 mitigation (flue gas decarbonization) in the algal suspension was 10-50% and decreased with increasing flue gas injection rate into the culture. A dissolved CO 2 partial pressure (pCO 2 ) higher than 0.1 kPa was maintained in the suspension at the end of the 50 m long culture area in order to prevent limitation of algal growth by CO 2 . NO X and CO gases (up to 45 mg m −3 NO X and 3 mg m −3 CO in flue gas) had no negative influence on the growth of the alga. On summer days the following daily net productivities of algae [g (dry weight) m −2 ] were attained in comparative parallel cultures: flue gas = 19.4-22.8; pure CO 2 = 19.1-22.6. Net utilization (η) of the photosynthetically active radiant (PAR) energy was: flue gas = 5.58-6.94%; pure CO 2 = 5.49-6.88%. The mass balance of CO 2 obtained for the flue gas stream and for the algal suspension was included in a mathematical model, which permitted the calculation of optimum flue gas injection rate into the photobioreactor, dependent on the time course of irradiance and culture temperature. It was estimated that about 50% of flue gas decarbonization can be attained in the photobioreactor and 4.4 kg of CO 2 is needed for production of 1 kg (dry weight) algal biomass. A scheme of a combined process of farm unit size is proposed; this includes anaerobic digestion of organic agricultural wastes, production and combustion of biogas, and utilization of flue gas for production of microalgal biomass, which could be used in animal feeds. A preliminary quantitative assessment of the microalgae production is presented.
Background: Selenium is a trace element performing important biological functions in many organis... more Background: Selenium is a trace element performing important biological functions in many organisms including humans. It usually affects organisms in a strictly dosage-dependent manner being essential at low and toxic at higher concentrations. The impact of selenium on mammalian and land plant cells has been quite extensively studied. Information about algal cells is rare despite of the fact that they could produce selenium enriched biomass for biotechnology purposes.
The freshwater alga Chlorella, a highly productive source of starch, might substitute for starch-... more The freshwater alga Chlorella, a highly productive source of starch, might substitute for starch-rich terrestrial plants in bioethanol production. The cultivation conditions necessary for maximizing starch content in Chlorella biomass, generated in outdoor scale-up solar photobioreactors, are described. The most important factor that can affect the rate of starch synthesis, and its accumulation, is mean illumination resulting from a combination of biomass concentration and incident light intensity. While 8.5% DW of starch was attained at a mean light intensity of 215 mmol/(m 2 s 1 ), 40% of DW was synthesized at a mean light intensity 330 mmol/(m 2 s 1 ). Another important factor is the phase of the cell cycle. The content of starch was highest (45% of DW) prior to cell division, but during the course of division, its cellular level rapidly decreased to about 13% of DW in cells grown in light, or to about 4% in those kept in the dark during the division phase. To produce biomass with high starch content, it is necessary to suppress cell division events, but not to disturb synthesis of starch in the chloroplast. The addition of cycloheximide (1 mg/L), a specific inhibitor of cytoplasmic protein synthesis, and the effect of element limitation (nitrogen, sulfur, phosphorus) were tested. The majority of the experiments were carried out in laboratory-scale photobioreactors, where culture treatments increased starch content to up to about 60% of DW in the case of cycloheximide inhibition or sulfur limitation. When the cells were limited by phosphorus or nitrogen supply, the cellular starch content increased to 55% or 38% of DW, respectively, however, after about 20 h, growth of the cultures stopped producing starch, and the content of starch again decreased. Sulfur limited and cycloheximide-treated cells maintained a high content of starch (60% of DW) for up to 2 days. Sulfur limitation, the most appropriate treatment for scaled-up culture of starchenriched biomass, was carried out in an outdoor pilot-scale experiment. After 120 h of growth in complete mineral medium, during which time the starch content reached around 18% of DW, sulfur limitation increased the starch content to 50% of DW.
A flue gas originating from a municipal waste incinerator was used as a source of CO 2 for the cu... more A flue gas originating from a municipal waste incinerator was used as a source of CO 2 for the cultivation of the microalga Chlorella vulgaris, in order to decrease the biomass production costs and to bioremediate CO 2 simultaneously. The utilization of the flue gas containing 10-13% (v/v) CO 2 and 8-10% (v/v) O 2 for the photobioreactor agitation and CO 2 supply was proven to be convenient. The growth rate of algal cultures on the flue gas was even higher when compared with the control culture supplied by a mixture of pure CO 2 and air (11% (v/v) CO 2 ). Correspondingly, the CO 2 fixation rate was also higher when using the flue gas (4.4 g CO 2 l −1 24 h −1 ) than using the control gas (3.0 g CO 2 l −1 24 h −1 ). The toxicological analysis of the biomass produced using untreated flue gas showed only a slight excess of mercury while all the other compounds (other heavy metals, polycyclic aromatic hydrocarbons, polychlorinated dibenzodioxins and dibenzofurans, and polychlorinated biphenyls) were below the limits required by the European Union foodstuff legislation. Fortunately, extending the flue gas treatment prior to the cultivation unit by a simple granulated activated carbon column led to an efficient absorption of gaseous mercury and to the algal biomass composition compliant with all the foodstuff legislation requirements.
Feedstuffs are routinely supplemented with various selenium sources, where organic forms of Se ar... more Feedstuffs are routinely supplemented with various selenium sources, where organic forms of Se are more bio-available and less toxic than the inorganic forms (selenites, selenates). When the algae are exposed to environmental Se in the form of selenite, they are able as other microorganisms to incorporate the element to different levels, depending on the algae species. Technology of heterotrophic fed-batch cultivation of the microalga Chlorella enriched by organically bound Se was developed, where the cultivation proceeds in fermentors on aerated and mixed nutrient solution with urea as a nitrogen and glucose as a carbon and energy source. High volumetric productivity and high cell concentrations (about 70-100 g Chlorella dry mass l −1 ) can be attained if nutrients and oxygen are adequately supplied. Addition of a small quantity of a new selenoprotein source-spray-dried Se-Chlorella biomass to the diet of farm animals had better effects on specific physiological and physical parameters of animals than selenite salt and was comparable with Se yeast added to the diet. This review introduces the importance of selenium for humans and animals, methods of Se determination, heterotrophic production of selenium-enriched Chlorella biomass in a fed-batch culture regime on organic carbon, and use of the biomass in animal nutrition.
Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2009
Background: Selenium is a trace element performing important biological functions in many organis... more Background: Selenium is a trace element performing important biological functions in many organisms including humans. It usually affects organisms in a strictly dosage-dependent manner being essential at low and toxic at higher concentrations. The impact of selenium on mammalian and land plant cells has been quite extensively studied. Information about algal cells is rare despite of the fact that they could produce selenium enriched biomass for biotechnology purposes.
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