Carbon dioxide fixation by microalgae photosynthesis using actual flue gas discharged from a boiler

Applied Biochemistry and Biotechnology - To mitigate the effects of carbon dioxide discharged from a boiler in a power plant, CO2 fixation by microalgae photosynthesis was studied. For the algae...     

Growth characteristics of microalgae in high-concentration co2 gas,effects of culture medium trace components,and impurities thereon

In order to reduce release of CO₂ contained in the flue gas from a power plant, we assumed a system in which the flue gas was directly blown into a pond and CO₂ was fixed on microalgae. We have experimentally examined the basic growth characteristics, such as trace components of culture medium, effects of impurities from exhaust gas, and light utilization rate of algal productivity, mainly forNonnochloropsis sp. NANNP-2 from SERI collection. Although Ni and V contained in heavy oil burnt ashes dissolve into culture solution, their concentrations are low, and they have no particular adverse effect on growth as impurities. Culture medium trace component (i.e., heavy metals and vitamins) are essential for the NANNP-2. However, for the PHAEO-2(Phaeodactylum sp.), the growth rate hardly changes, even if vitamins and heavy metals other than Fe are eliminated.     

Microbial removal of sulfur dioxide from a gas stream with net oxidation to sulfate

A study has been conducted of the feasibility of utilizing the sulfate reducing bacteriumDesulfovibrio desulfuricans and the chemoautotrophThiobacillus denitrificans as a basis of a microbial process for the removal of sulfur dioxide from a gas with net oxidation to sulfate. In reactors-in-series, SO₂ was reduced to H₂S in the first stage by D.desulfuricans. The H₂S was then stripped with nitrogen and sent to a second stage where it was oxidized to sulfate by T.denitrificans. A sulfur balance demonstrated complete reduction of SO₂ to H₂S in the first stage and complete oxidation of H₂S to sulfate in the second stage.     

Production of methyl ester fuel from microalgae

Microalgae are unique photosynthetic organisms that are known to accumulate storage lipids in large quantitites and thrive in saline waters. Before these storage lipids can be used, they must be extracted from the microalgae and converted into usable fuel. Transesterification of lipids produces fatty acid methyl esters that can be used as a diesel fuel substitute. Three solvents, 1-butanol, ethanol, and hexane/2-propanol, were evaluated for extraction efficiency of microalgal lipids. Type of catalyst, concentration of catalyst, time of reaction, temperature of reaction, and quality of lipid were examined as variables for transesterification. The most efficient solvent of the three for extraction was 1-butanol (90% efficiency), followed by hexane/2-propanol and ethanol. Optimal yield of fatty acid methyl esters was obtained using 0.6N hydrochloric acid in methanol for 0.1 h at 70°C.     

Microbial reduction of SO2 as a means of byproduct recovery from regenerable,dry scrubbing processes for flue gas desulfurization

A project is under way at the University of Tulsa to investigate the reduction of SO₂ to H₂S by sulfate reducing bacteria (SRB) in co-culture with mixed fermentative heterotrophs. We have previously demonstrated that SO₂ is completely reduced to H₂S (contact times of 1–2 s) in cultures in which no redox poising agents were required and glucose served as the ultimate source of carbon energy. We have proposed that such a microbial process could be coupled with a Claus reactor to recover elemental sulfur as a byproduct of regenerable, dry scrubbing processes for flue gas desulfurization. The development of this process concept has continued with a study of the use of molasses as a source of carbon and reduced nitrogen, identification of important non-SRB heterotrophs in process cultures, and the identification of the end products of carbohydrate fermentation that serve as carbon and energy sources for the SRB and identification of the end products of SRB metabolism.     

Sulfur gas tolerance and toxicity of co-utilizing and methanogenic bacteria

Anaerobic bacteria have been shown to be capable of converting CO, H₂, and CO₂ in synthesis gas to valuable products, such as acetate, methane, and ethanol. However, synthesis gas also contains small quantities of sulfur gases such as H₂S and COS, that may inhibit the performance of these organisms. This paper compares the performance of several CO-utilizing and methanogenic bacteria in converting CO, CO₂, and H₂ to products in the presence of various concentrations of H₂S and COS. The sulfur gas toxicity levels, growth, substrate uptake, and product formation for each organism are compared.     

Bioelectrosynthesis as an alternative to photosynthesis

The CO₂ reduction processes have been discussed as a way of designing an ecologically totally closed technology. An electric current and molecular hydrogen are the two related available agents that can be discussed as ecologically pure reductants. The most important products are liquid and gaseous fuels, the products of large-scale organic synthesis, monomers, and amino acids. For CO₂ reduction, the necessary energy consumption and H₂ costs were calculated. For complex organic molecules, amino acids for instance, the energy consumption does not make up the main portion of the costs. The biocatalytic systems of CO₂ reduction based on cryoimmobilized cells are described. Conversion of CO₂ into L-lysine with electrochemical decomposition of water was effected on the laboratory scale. A general unit for diverse technological processes can be a bioelectrosynthetic Index Entries: Bioelectrosynthesis; CO₂ reduction; liquid fuels; amino acids; immobilized cells; economic estimates. modulus, an electrochemical hydrogen generator coupled with a biocatalytic converter of hydrogen and oxygen. The systems for bioelectrosynthesis of motor fuels and essential amino acids have been economically estimated and characterized. The possibilities of combining the solar energy transformation and H₂–CO₂ conversion have been discussed.     

Methane production from synthesis gas using a mixed culture ofR. rubrum M. barkeri,and M. formicicum

The components of synthesis gas, CO, H₂, and CO₂, may be converted into CH₄ biologically through either acetate or H₂/CO₂ as intermediates. Of these two routes, conversion through H₂/CO₂ is preferred. This paper presents results of mixed-culture studies employing the photosynthetic bacteriumR. rubrum for converting CO to CO₂ and H₂ by the water gas shift reaction and two methanogens,M. formicicum andM. barkeri, for converting CO₂ and H₂ into CH₄. Results are presented for triculture operation in two types of reactors, the packed bubble column and the trickle-bed reactor.     

Reduction of nitric oxide by denitrifying bacteria

Two heterotrophic denitrifying bacteria,Paracoccus denitrificans andPseudomonas denitrificans, have been shown to utilize nitric oxide (NO) as a terminal electron acceptor and succinate, yeast extract, and heat/alkali pretreated municipal sewage sludge as carbon and energy sources. Complete removal of NO (0.50%) from a feed gas sparged into the cultures was observed. It is suggested that reduction of NO may be a common feature of denitrifying bacteria and that a microbial process to dispose of NO_x may be economically viable.     

Carbon dioxide fixation by microalgal photosynthesis using actual flue gas from a power plant

Applied Biochemistry and Biotechnology - CO2 fixation by microalgal cultures, a potential method for CO2 emissions mitigation, was studied in small (approx 2 m2) ponds using actual flue gas from...     

γ-linolenic acid production by microalgae

The production of γ-linolenic acid from algae in fresh and marine water was investigated. WhenSpirulina platensis was left in the dark condition, it contained about one and a half times γ-linolenic acid compared with conventionalSpirulina platensis. Marine microalga,Chlorella sp. NKG 042401 contained about 10% of γ-linolenic acid. The highest γ-linolenic acid content was obtained when this alga was cultured under the radiation of around 100 μEinstein/m²/s.     

Urease purification from the seeds ofCajanus Cajan and its application in a biosensor construction

Urease has been purified from the seeds of Cajanus Cajan. The purification process involves three solvent extraction steps followed by DEAE-cellulose column chromatography. The specific activity of the purified enzyme is found to be 1920 U/mg with the recovery of 8%. The application of the purified enzyme in a biosensor construction is discussed.     

Increased oxygen transfer in a yeast fermentation using a microbubble dispersion

A microbubble dispersion (MBD) was used to supply oxygen for aerobic fermentations in a standard 2 L stirred tank fermenter. The microbubble dispersion was formed using only surfactants produced naturally. Growth rates ofSaccharomyces cerevisiae cultures were found to be equal or greater with MBD sparging than with gas sparging. The oxygen transfer coefficent with MBD sparging was found to be 190/h and independent of impeller speed from 100–580 rpm. The oxygen transfer coefficient with air sparging rose from 55 to 132/h over the same range of impeller speeds. Power requirements for the fermenter systems were estimated.     

Production of citronellyl acetate in a fed-batch system using immobilized lipase

Several reports exist in the literature citing the decrease in conversion rates of organic-phase catalytic synthesis reactions when acetic acid is present as a reaction component. This inhibition is thought to result from damage to either the hydration layer-protein interaction or the overall enzyme structure. In this work, the inhibitory effect of acetic acid on lipase enzyme activity was ameliorated by conducting syntheses under acetic acid-limiting conditions in a fed-batch system, resulting in higher product yields. Periodic additions of acetic acid at levels of 40 mM or less gave maximum yields of 65% conversion for the reaction of citronellol and acetic acid to form citronellyl acetate. The enzyme used was a fungal lipase fromMucor miehei, and was immobilized on macroporous synthetic resin (a Novo lipozyme Novo Nordisk, Denmark). These results represent a fourfold improvement over batch runs reported in the literature for direct esterification of terpene alcohol with acetic acid using lipozyme as a catalytic agent.     

Ethanol from lignocellulosic wastes with utilization of recombinant bacteria

This article presents the advanced technology that has been developed by BioEnergy International of Gainesville, Florida, utilizing novel recombinant strains of bacteria developed by Lonnie Ingram of the University of Florida. The first commercial applications of these unique fermenting organisms convert 5-carbon sugars, as well as 6-carbon sugars, and oligomers of cellulose (e.g., cellobiose and cellotriose) directly to ethanol. The proposed systems that will be utilized for conversion of agricultural wastes, mixed waste papers, and pulp and paper mill waste in forthcoming commercial installations are now under design. This involves the extensive experience of Raphael Katzen Associates International, Inc. in acid hydrolysis, enzyme production, enzymatic hydrolysis, large-scale fermentation engineering, and distillation/dehydration. Specific examples of this advanced technology will be presented in different applications, namely:

Stimulation of hydrogen production in algal cells grown under high CO2 concentration and low temperature

When cells ofChlamydomonas sp. MGA 161, a marine green alga, were cultivated at a high CO₂ concentration (15% CO₂) and low temperature (15°C), the growth lag time was much longer, but the starch accumulated was two times higher than under the basal conditions (5% CO₂ 30°C). When the cells grown in the high-CO₂/low-temperature conditions were incubated under dark anaerobic conditions, the degradation of starch and production of hydrogen and ethanol were remarkably higher than those grown under the basal conditions. The lag time of cell growth was shortened, whereas the high capacity of starch accumulation and hydrogen production was maintained, by cultivating the cells alternately every 12 h under the basal and high-CO₂/low-temperature conditions. Using this dual system, in which the cultivation was alternated between the two conditions, the total productivity was significantly improved.     

Immunologic relatedness of extracellular ligninases from the actinomycetesstreptomyces viridosporus t7a andstreptomyces badius 252

Four isoforms of the extracellular lignin peroxidase of the ligninolytic actinomyceteStreptomyces viridosporus T7A (ALip-P1, P2, P3, and P4) were individually purified by ultrafiltration and ammonium sulfate precipitation, followed by electro-elution using polyacrylamide gel electrophoresis. Three of the purified peroxidases were compared for their immunologic relatedness by Western blot analysis using a polyclonal antibody preparation produced in rabbits against pure isoform P3. The anti-P3 antibody was also tested for its reactivity towards a lignin peroxidase from the white-rot fungusPhanerochaete chrysosporium and another ligninolytic actinomyceteStreptomyces badius 252. Results showed that peroxidases ALip-P1 through ALip-P3 are immunologically related to one another. The peroxidases ofS. badius, but not the peroxidase ofP. chrysosporium, also reacted with the antibody, thus indicating that the lignin peroxidases ofS. viridosporus andS. badius are immunologically related. Based upon its specific affinity, lignin peroxidase isoform ALip-P3 ofS. viridosporus was readily purified using an anti-P3 antibody affinity column.     

Preparation of Tyr-C-peptide from genetically altered human insulin precursor

C-peptide radioimmunoassay (C-peptide RIA) is widely used in determination of pancreatic B-cell secretion activity.¹²⁵I labeled TyrC-peptide is indispensable in C-peptide RIA kit. Herein we discuss a way of obtaining recombinant Tyr-C-peptide. Arg32Tyr human proinsulin mutant (R32Y-proinsulin) gene was constructed by site-directed mutagenesis and overexpressed inEscherichia coli. Purified R32Y-proinsulin was converted to insulin and Tyr-C-peptide by trypsin and carboxypeptidase B codigestion. Tyr-C-peptide was isolated through reverse-phase HPLC (RP-HPLC) and identified by C-peptide RIA and amino acid analysis.     

Simultaneous saccharification and fermentation of lignocellulose

Simultaneous saccharification and fermentation (SSF) processes for producing ethanol from lignocellulose are capable of improved hydrolysis rates, yields, and product concentrations compared to separate hydrolysis and fermentation (SHF) systems, because the continuous removal of the sugars by the yeasts reduces the end-product inhibition of the enzyme complex. Recent experiments using Genencor 150L cellulase and mixed yeast cultures have produced yields and concentrations of ethanol from cellulose of 80% and 4.5%, respectively. The mixed culture was employed because B.clausenii has the ability to ferment cellobiose (further reducing end-product inhibition), while the brewing yeastS. cerevisiae provides a robust ability to ferment the monomeric sugars. These experimental results are combined with a process model to evaluate the economics of the process and to investigate the effect of alternative processes, conditions, and organisms.