Mixed Algal Culture Research Articles

Efficiency of lipid accumulating Actinomycetes isolated from soil for biodiesel production: Comparative study with microalgae

ABSTRACT Due to the global warming and the increase of toxic gases emitted from the fossil fuels and the increase of energy demand, it is necessary to look for alternative sources for biodiesel. In this work, fifty bacterial species were isolated from soil samples and the isolated bacteria were tested for their ability of lipid production. The most potent lipid producer was identified as Streptomyces coelicolor A3-NC:003888.3 using the 16S rDNA partial sequencing technique. The lipid production process was performed in a bench scale for pure S. coelicolor, Chlorella vulgaris (as a standard biodiesel producer) and mixed algal bacterial culture as a comparative study. The results indicated that 93% wt of fatty acids of Streptomyces was converted to the corresponding fatty acid methyl esters (biodiesel). After transesterification of the produced lipids, the obtained oil was characterized according to American Society for Testing and Materials (ASTM) standards. The density of bacterial biodiesel was 0.866 and that of algal biodiesel was 0.797; also the specific gravity was 0.866 and 0.784 for bacterial and algal biodiesel, respectively, giving more lubricant characters for bacterial biodiesel. The gross heating value of bacterial biodiesel (43426 Kj/Kg) was higher than that of algal biodiesel (41896 Kj/Kg), dependently, the cetane number of bacterial biodiesel (38) was little lower than that of algal biodiesel (43).

Microfiltration of algae: Impact of algal species, backwashing mode and duration of filtration cycle

The objective of this study was to investigate and compare the microfiltration characteristics of mixed algal cultures containing two species of green microalgae: Chlorella vulgaris and Chlamydomonas reinhardtii. Submerged membrane filtration experiments with 300mgL−1 suspensions of pure algal cultures indicated that while membrane fouling potential was comparable in both cases, Chlorella vulgaris had a lower cake formation potential. Filtration experiments were carried out with 1000mgL−1 suspensions of mixed algal culture over several 12-h cycles with backwashing, either in the on-line or off-line mode. While on-line backwashing caused more fouling, this did not significantly affect the flux through the membrane, which was controlled by the cake formation on the membrane. The algal mixed culture was also filtered over many 3-h cycles with on-line backwashing. Lower cycle duration resulted in lower average cake resistance and hence allowed more membrane throughput, but at the cost of more frequent backwashing. Chemical washing of the membrane could remove the fouling resistance only partially. Thus, despite periodic chemical washing, the intrinsic membrane resistance increased consistently with cumulative throughput through the membrane.

Performance Of Chlorella Vulgaris, Neochloris Oleoabundans, and mixed indigenous microalgae for treatment of primary effluent, secondary effluent and centrate

The objective of this study was to investigate and compare the growth rate and treatment efficiency of Chlorella vulgaris, Neochloris oleoabundans and mixed indigenous microalgae for the removal of organic carbon, nitrogen and phosphorus from primary effluent, secondary effluent, and centrate. The indigenous microalgae culture was collected from a wastewater treatment plant, and performed better than Chlorella vulgaris and Neochloris oleoabundans in removing inorganic nitrogen (63.2–80.8%), phosphorus (30.8–70%) and chemical oxygen demand (64.9–70.4%) in all samples. The growth rates were different not only among the three microalgae cultivated in the same wastewater but also for the same microalgae cultivated in different wastewaters. The highest growth rate for C. vulgaris (0.61day−1) and N. oleoabundans (0.35day−1) occurred in primary wastewater with a C:N:P ratio of 24:5:1, and for mixed algal culture (0.41day−1) occurred in centrate with a C:N:P ratio of 4.4:1:1.5. In addition, primary effluent, secondary effluent, and centrate samples that were treated with the mixed indigenous microalgae showed remarkably different microalgae populations and distribution of species after the treatment.

Resolving Mixed Algal Species in Hyperspectral Images

We investigated a lab-based hyperspectral imaging system's response from pure (single) and mixed (two) algal cultures containing known algae types and volumetric combinations to characterize the system's performance. The spectral response to volumetric changes in single and combinations of algal mixtures with known ratios were tested. Constrained linear spectral unmixing was applied to extract the algal content of the mixtures based on abundances that produced the lowest root mean square error. Percent prediction error was computed as the difference between actual percent volumetric content and abundances at minimum RMS error. Best prediction errors were computed as 0.4%, 0.4% and 6.3% for the mixed spectra from three independent experiments. The worst prediction errors were found as 5.6%, 5.4% and 13.4% for the same order of experiments. Additionally, Beer-Lambert's law was utilized to relate transmittance to different volumes of pure algal suspensions demonstrating linear logarithmic trends for optical property measurements.

Evaluation of DNA extraction methods for freshwater eukaryotic microalgae

The use of molecular methods to investigate microalgal communities of natural and engineered freshwater resources is in its infancy, with the majority of previous studies carried out by microscopy. Inefficient or differential DNA extraction of microalgal community members can lead to bias in downstream community analysis. Three commercially available DNA extraction kits have been tested on a range of pure culture freshwater algal species with diverse cell walls and mixed algal cultures taken from eutrophic waste stabilization ponds (WSP). DNA yield and quality were evaluated, along with DNA suitability for amplification of 18S rRNA gene fragments by polymerase chain reaction (PCR). QiagenDNeasy® Blood and Tissue kit (QBT), was found to give the highest DNA yields and quality. Denaturant Gradient Gel Electrophoresis (DGGE) was used to assess the diversity of communities from which DNA was extracted. No significant differences were found among kits when assessing diversity. QBT is recommended for use with WSP samples, a conclusion confirmed by further testing on communities from two tropical WSP systems. The fixation of microalgal samples with ethanol prior to DNA extraction was found to reduce yields as well as diversity and is not recommended.

Coupled nutrient removal and biomass production with mixed algal culture: Impact of biotic and abiotic factors

The influence of biotic (algal inoculum concentration) and abiotic factors (illumination cycle, mixing velocity and nutrient strength) on the treatment efficiency, biomass generation and settleability were investigated with selected mixed algal culture. Dark condition led to poor nutrient removal efficiency. No significant difference in the N, P removal and biomass settleability between continuous and alternating illumination was observed, but a higher biomass generation capability for the continuous illumination was obtained. Different mixing velocity led to similar phosphorus removal efficiencies (above 98%) with different retention times. The reactor with 300rpm mixing velocity had the best N removal capability. For the low strength wastewater, the N rates were 5.4±0.2, 9.1±0.3 and 10.8±0.3mg/l/d and P removal rates were 0.57±0.03, 0.56±0.03 and 0.72±0.05mg/l/d for reactors with the algal inoculum concentration of 0.2, 0.5 and 0.8g/l, respectively. Low nutrient removal efficiency and poor biomass settleability were obtained for high strength wastewater.

Experimental and mathematical model of the interactions in the mixed culture of links in the “producer–consumer” cycle

The paper presents a experimental and mathematical model of interactions between invertebrates (the ciliates Paramecium caudatum and the rotifers Brachionus plicatilis) in the “producer–consumer” aquatic biotic cycle with spatially separated components. The model describes the dynamics of the mixed culture of ciliates and rotifers in the “consumer” component, feeding on the mixed algal culture of the “producer” component. It has been found that metabolites of the algae Scenedesmus produce an adverse effect on the reproduction of the ciliates P. caudatum. Taking into account this effect, the results of investigation of the mathematical model were in qualitative agreement with the experimental results. In the “producer–consumer” biotic cycle it was shown that coexistence is impossible in the mixed culture of invertebrates of the “consumer” component. The ciliates P. caudatum are driven out by the rotifers B. plicatilis.

Which are fatty acids of the green alga Chlorella?

Fatty acid composition of three species of Chlorella were studied under conditions of photoautotrophic and heterotrophic cultivation, nitrogen starvation, and outdoor in a photobioreactor. The composition 14:0, 16:0, 16:1, 16:2, 16:3, 18:0, 18:1, 18:2, α-18:3 is confirmed for Chlorella. Fatty acids with 20 carbon atoms and four or five double bonds are considered not originating from Chlorella. Other exceptions of this composition are interpreted as mixed algal culture, bacterial contamination or impurities.

Photocatalytic Inhibition of Microbial Adhesion by Anodized Titanium

Biofouling is one of the concerns in the use of titanium for seawater cooled condensers of power plants. Earlier studies have shown that anodized titanium and its alloys with a thin film of anatase (TiO2) on its surface can inhibit attachment of Pseudomonas sp. when illuminated with near-UV light (350 - 380 nm). In the present study, a comparison of the photocatalytic inhibition of microbial attachment on titanium surfaces anodized at different voltages was carried out. Thin films of anatase of varying thickness were produced on titanium grade-2 by anodizing in dilute orthophosphoric acid solution at 30 V, 50 V and 100 V. The photocatalytic efficiency of these anodized surfaces was measured by the methylene blue degradation method. The anodised surfaces were exposed to liquid cultures of Gram-negative Pseudomonas sp., Gram-positive Micrococcus sp. and to a mixed algal culture. Photocatalytic inhibition of microbial attachment was maximum on the titanium surface anodized at 30 V, followed by the surface anodized at 50 V and then at 100 V. The photocatalytic inhibition of microbial attachment was also found to be dependent on the cell wall characteristics of the organism. The Gram-negative Pseudomonas sp. with a lipoproteinaceous outer membrane was the most susceptible to the photocatalytic effect, while the Gram-positive Micrococcus sp. with peptidoglycan cell wall showed moderate susceptibility and the algae with siliceous cell wall showed no susceptibility at all.

A mathematical model of the interactions in the mixed culture of invertebrates and algae in the “producer–consumer” aquatic biotic cycle

This paper presents a mathematical model of interactions between two herbivorous invertebrates (ciliate Paramecium caudatum and rotifer Brachionus plicatilis) and two planktonic algae (Chlorella vulgaris and Scenedesmus quadricauda) spatially segregated in two compartments of a chemostat–type experimental microcosm system. The model mimics a “producer–consumer” aquatic biotic cycle, describing the dynamics of the mixed culture of ciliates and rotifers, as “consumer” compartment, feeding on the mixed algal culture, as “producer” compartment, under N-limiting conditions. We experimentally found that metabolites of the alga Scenedesmus produce an adverse effect on the reproduction of ciliate Paramecium. Taking this effect into account improved the behavior of the model, the results of which came into qualitative agreement with the experimental results. Both our experimental and modeling approaches demonstrated that, even in conditions of a spatially–segregated “producer-consumer” biotic cycle, species coexistence is impossible either in the mixed algal culture or in the mixed invertebrate culture. Scenedesmus excluded Chlorella, whereas Brachionus excluded Paramecium.

Competition between Populations in the Consumer–Producer Trophic Chain in a Closed Aquatic System

The functioning of a closed aquatic consumer–producer system with spatially separated links, with each link consisting of two species, is considered. Competition between the consumers (infusorians Paramecium caudatum and rotifers Brachionus sp.) feeding on a mixed algal culture (Chlorella vulgaris and Scenedesmus sp.) and competition between these algae under conditions of limited nitrogen supply are analyzed. It is shown that Scenedesmus algae have an advantage over C. vulgaris in terms of competitiveness, and their metabolic products have an adverse effect on reproduction in infusorians.

A comparative study on growth performance and biochemical composition of mixed culture of Isochrysis galbana and Chaetoceros calcitrans with monocultures

The growth performance, biochemical composition and nutritive value of the mixed culture of Isochrysis galbana and Chaetoceros calcitrans, grown in batch cultures under laboratory conditions was compared with those in monoculture conditions. In mixed culture, both species manifested their monoculture characteristics with some variations: I. galbana, as in its monoculture situation, had an initial rapid growth, while the growth rate of C. calcitrans was half that of its monoculture state. However, as the growth rate of C. calcitrans increased gradually during later stages of the experiment that of I. galbana decreased. Although C. calcitrans dominated the mixed culture during later stages, the population of I. galbana was not totally eliminated. Cellular concentrations of chlorophyll a, protein, carbohydrate, lipid and particulate organic carbon in monocultures and mixed culture peaked during the late exponential phase but were significantly higher ( P<0.05) in the mixed culture. The calculated dietary energy content was also significantly higher ( P<0.05) in the mixed culture compared to the monocultures during all the growth phases. The study highlights the nutritional implications of mixed algal cultures in hatcheries, particularly in shrimp hatcheries where different species and size groups of larvae are to be fed.

Growth characteristics of Heterosigma akashiwo virus and its possible use as a microbiological agent for red tide control.

The growth characteristics of Heterosigma akashiwo virus clone 01 (HaV01) were examined by performing a one-step growth experiment. The virus had a latent period of 30 to 33 h and a burst size of 7.7 x 10(2) lysis-causing units in an infected cell. Transmission electron microscopy showed that the virus particles formed on the peripheries of viroplasms, as observed in a natural H. akashiwo cell. Inoculation of HaV01 into a mixed algal culture containing four phytoplankton species, H. akashiwo H93616, Chattonella antiqua (a member of the family Raphidophyceae), Heterocapsa triquetra (a member of the family Dinophyceae), and Ditylum brightwellii (a member of the family Bacillariophyceae), resulted in selective growth inhibition of H. akashiwo. Inoculation of HaV01 and H. akashiwo H93616 into a natural seawater sample produced similar results. However, a natural H. akashiwo red tide sample did not exhibit any conspicuous sensitivity to HaV01, presumably because of the great diversity of the host species with respect to virus infection. The growth characteristics of the lytic virus infecting the noxious harmful algal bloom-causing alga were considered, and the possibility of using this virus as a microbiological agent against H. akashiwo red tides is discussed.

フォトクロミズムを用いた光遮蔽による藻類過剰増殖抑制の可能性

In the past few decades, eutrophication in closed water areas has been becoming a serious problem on the use of water for drinking, agriculture, recreation, and other purposes. Especially, excessive phytoplankton growth seriously degrades the environment and aquatic ecosystems; algal blooms, lose of oxygen, fish kills, loss of biodiversity, and other problems. This paper intends to investigate control and prevention of the excessive phytoplankton growth by reducing light levels below those necessary for photosynthesis. To shield sunlight, photochromic (PC) films, which show photochromism such as colorless forms turn to colored forms by ultraviolet irradiation, were prepared. The PC films containing Spironaphthoxazine as a photochromic compound showed excellent photocoloration (75 to 80% absorbance at 600nm) under sunlight irradiation, and they maintained the photocoloration ability, at least longer than a month. However the results of algal growth potential tests with the PC films were the oppsite to what we had expected. While the growth of mixed algal cultures was controlled with the PC films under sunlight irradiation, the application of the PC films was not successful for the prevention of pure cultures M. aeruginosa growth. It was probably attributable to the difference between the wavelength for the PC films' maximum absorbance (approximately 600nm) and the available wavelength for photosynthesis (approximately 680nm). The absorbance at 680nm by PC films was approximately 20%.

13C and 15N NMR spectroscopic investigation on the formation of fossil algal residues

13C and 15N NMR spectroscopy was applied to modern (a mixed algal culture, its algaenan and its compost), ancient (algal derived sediments from Mangrove Lake, Bermuda) and fossilized algal residues (Torbanite, Green River Shale) for the purpose of establishing the forms of nitrogen algal remains and evaluating their long-term stabilities. The results indicate that proteinaceous material can resist microbial degradation in sediments as old as 4000 yr, possibly in refractory biopolymers, by encapsulation into their macromolecular network. The 15N NMR spectra of the Torbanite and the Green River Shale show a relative enrichment of heterocyclic-N, which may derive from selective preservation of biogenic heterocyclic compounds or by rearrangement of peptide chains during diagenesis.

Growth of harmful marine algae in multispecies cultures

Mixtures of harmful and harmless algae were grown in discontinuously diluted batch cultures under ammonium, nitrate and phosphate limitation, and at different irradiances (20-500 jjjnol quanta m s~'). The species used were Chrysochromulina polylepis, Emiliania huxleyi type B, Rhodomonas sp., the dinoflagellales Fibrocapsa japonica, Gymnodinium simplex, Gyrodinium aureolum, Heterocapsa triquetra, Heterosigma carterae, Prorocentrum micans and Alexandrium tamarense, the diatoms Chaetoceros socialis, Cymatosira belgica, Ditylum brightwellii, Laudcria borealis, Odontelta aunla, Pseudonitzschia pungens, Streptotheca tamesis, and the cyanobacterium Synechococcus. Their growth response in the mixed algal cultures is discussed in relation to their abundance in different natural habitats. In comparison with the other non-diatoms, the mixotrophic Cpolylepis grew fast under all tested nutrient and light limitations. Emiliania huxleyi grew well under nitrogen (N) limitation (with nitrate as N source) and at irradiance levels from 15 up to 500 u.mol quanta m~ s. No growth of calcifying cells could be detected under N limitation when ammonium was used as N source. Rhodomonas grew reasonably well under ammonium-N limitation and grew fast at the highest irradiance. The dinoflagellates were poor competitors compared to the Prymnesiophyceae. The environmental fitness of the Prymnesiophyceae appears to be closely related to the reproductive capacity of the vegetative stage, whereas the natural distribution of dinoflagellates seems more closely dependent on the generative reproduction-related specific life cycle characteristics of the individual species. The marine diatoms include a mixture of both types of species. Some marine diatom species clearly have the capability to outcompete non-diatoms under different types of nutrient and light limitations when silicate is in excess. Other diatoms seem to be poor competitors.

Effect of growth and subsequent decomposition of blue-green algae on the transformation of iron and manganese in submerged soils

N2-fixing blue-green algae (Cyanobacteria), besides enriching soils with N and organic carbon, may modify a number of chemical and electro-chemical properties of the soils resulting in a change in availability of some micronutrient elements. Keeping this in view, an experiment was conducted to study the effects of growth and subsequent decomposition of blue-green algae on changes in the different forms of Fe and Mn in four soils under submerged condition. A mixed algal culture containing Anabaena, Nostoc, Cylindrospermum, and Tolypothrix was used as inoculum. It was allowed to grow for 2 months, after which the soils were sequentially extracted with (i) M NH4OAc (pH 7.0), (ii) M K4P2O7, (iii) 0.1 M NH2OH.HCl (pH 2.0), (iv) 0.2 M (NH4)2C2O4 (pH 3.0) and (v) 0.1 M ascorbic acid to obtain water-soluble plus exchangeable, organically bound, easily reducible, amorphous oxides-and crystalline oxides-bound forms of Fe and Mn, respectively, both during the growth as well as the subsequent in-situ decomposition of the algal biomass in soils. Iron and Mn in the extracts were estimated by atomic absorption spectrophotometry.

The influence of light/dark cycles in mixed algal cultures on their productivity

In mass algal cultures, some form of agitation is usually provided, which amongst others, moves the organisms though an optically dense profile. During this transport, fluctuations in the light energy supply are perceived by the algae, which are of the order of 1 Hz and less. Additional to these variations the cultures are subject to diurnal, seasonal and climatic light variations. It has been suggested that turbulence with the resultant light/dark cycles enhances their productivity. However, turbulence has two major influences on an organism, i.e. it facilitates fluctuating light regimes and decreases the boundary layer which results in an increased exchange rate between the organism and its environment. With the aid of oxygen liberation measurements, the influence of fluctuating light regimes on productivity was measured. No simple relation existed, but no enhancement of productivity could be shown at cycles of 1-0·0038 Hz. Short term physiological changes were found to influence productivity severely.

Studies on the Effect of Cell Division‐inhibiting Herbicides on Unialgal and Mixed Algal Cultures

AbstractThe effect of two cell division inhibiting herbicides on unialgal and mixed algal cultures was studied in laboratory tests. The herbicides studied were trifluralin (analytical grade) and the active ingredient as well as the preparation (80 % a.i.) of diphenamid. The three green algal species used were Selenastrum capricornutum PRINTZ, Scenedesmus quadricauda (TURP.) BREB., Oocystis parva W. et G. S. WEST. The response of algae to herbicides was determined by cell counting, and measured by turbidity (750 nm) and the 02‐production of some of the treated cultures.The EC50‐value (96 h) of trifluralin to Selenastrum capricornutum was 3.3 mg/l. There were differences in the sensitivity of the three algal strains to the diphenamid; the EC50‐values to Selenastrum, Scenedesmus and Oocystis were 16.7, 10.1 and 6.3 mg/l, respectively. The lag phase observed in the growth of the treated cultures caused by diphenamid was verified by O2‐measurements. The preparation of diphenamid was not as effective as the active ingredient. In mixed cultures the ratio between two different algal strains depended both on the concentration of the diphenamid and the sensitivity of the two strains.

Use of a mixed algal culture to characterize industrial wastewaters

A mixture of five freshwater algae was cultivated with additions of wastewater samples from chemical, mining, polyvinylchloride, textile, paper mill, and oil refinery industries. Two water samples from chemical industries and one from an oil refinery stimulated the algal growth in a nutrient-poor medium, while growth in other samples, including a nutrient-rich medium, was inhibited in several different ways. For eight of the water samples a delayed growth of 2–4 days was noted. Decreased growth rate and lowered maximal biomass occurred in seven of the samples. The photosynthetic capacity of the algal cells was measured by using in vivo fluorescence of chlorophyll a. These quick measurements mostly agreed with those of the growth rates. When the species composition of the mixed algal culture was investigated, large differences in sensitivities between the different species were found. Stimulation or inhibition were observed in the same sample for different species but also for the same species at different concentrations.