Mixed Culture Of Microalgae Research Articles

Short and long-term experiments on the effect of sulphide on microalgae cultivation in tertiary sewage treatment

Microalgae cultivation appears to be a promising technology for treating nutrient-rich effluents from anaerobic membrane bioreactors, as microalgae are able to consume nutrients from sewage without an organic carbon source, although the sulphide formed during the anaerobic treatment does have negative effects on microalgae growth. Short and long-term experiments were carried out on the effects of sulphide on a mixed microalgae culture. The short-term experiments showed that the oxygen production rate (OPR) dropped as sulphide concentration increased: a concentration of 5mgSL−1 reduced OPR by 43%, while a concentration of 50mgSL−1 came close to completely inhibiting microalgae growth.The long-term experiments revealed that the presence of sulphide in the influent had inhibitory effects at sulphide concentrations above 20mgSL−1 in the culture, but not at concentrations below 5mgSL−1. These conditions favoured Chlorella growth over that of Scenedesmus.

Extraction of sugars from mixed microalgae culture using enzymatic hydrolysis: Experimental study and modeling

ABSTRACTThe efficient production of reducing sugars is an extremely important requirement in the utilization of microalgae as a feedstock in bioethanol production. In this study, for the first time, the time course of reducing sugar production during starch hydrolysis of mixed microalgal biomass under different operational conditions was modeled by two different methods: a-Michaelis–Menten’s kinetic model and b-artificial neural network (ANN) method. The results from both models revealed that predicted values are in good agreement with the experimental results. Also, sensitivity analysis indicated that the kinetic model results are less sensitive to Km and Ki than to . The applied ANN was a feed-forward back propagation network with Levenberg–Marquardt algorithm. It was found that the order of relative importance of the input variables on reducing sugar concentration predicted by ANN model was as follows: pH > substrate concentration > temperature > hydrolysis time. Subsequently, the results indicated that the maximum reducing sugar yield (96.3%) was achieved by adding enzymes with the sequence of first cellulases, at 50°C, pH 4.5, second α-amylase, at 70°C, and pH 6 with a substrate concentration of 50 g/L. These findings may be useful for improving the enzymatic hydrolysis of mixed microalgae for bioethanol production.

Bioethanol production from acidic and enzymatic hydrolysates of mixed microalgae culture

Mixed microalgae cultures are considered as an attractive research area compared to traditional pure culture to dominate cultivation contamination risk and enhance economic feasibility of large-scale biofuel production. However, pre-treatment and bioethanol production from mixed microalgae culture has not been reported yet. Therefore, this study was aimed to evaluate the effect of different pre-treatment strategies including acidic, alkaline, and enzymatic hydrolysis on the sugar extraction from mixed microalgae. Besides, the effects of MgSO4 and CaCl2 as lewis acids in acidic pre-treatment on reducing sugar yield were studied.Results showed that the mixture of dilute sulfuric acid and MgSO4 exhibited a higher sugar yield than dilute acid. Among all pre-treatments used, the enzymatic treatment with thermostable enzymes showed the highest recovery of 0.951g extracted glucose/g total sugar. Moreover, the enzymatic pre-treatment of wet microalgae was compared with dried ones at identical operational conditions and dried biomass concentration of 50g/l, similar sugar yields were achieved which would be advantageous to reduce the need for drying of the microalgae biomass. Fermentation of the acidic and enzymatic treated samples to ethanol using Saccharomyces cerevisiae showed yield of 0.38 and 0.46g/g glucose, corresponding to 76% and 92% of the theoretical values, respectively. The obtained results revealed that bioethanol yield after enzymatic hydrolysis of mixed microalgae culture are higher than those of acid hydrolysis.

Chemical composition and in vitro anti-algal activity of Potamogeton crispus and Myriophyllum spicatum extracts

The aim of this work was to investigate and compare the phytochemical constituents and anti-algal activities of crude extracts from dry macrophytes species, Potamogeton crispus and Myriophyllum spicatum. Organic solvents differed in polarity including petroleum ether, methylene chloride, chloroform, acetone and methanol were used to extract the phytochemical compounds and gas chromatograph–mass spectrometry (GC–MS) analyzer was used for the detection of these compounds. Generally, the results indicated that the composition and mass fraction of phytochemical constituents varied with plant species and extraction solvents. The growth inhibition effects of separate and mixed plants extracts on Pseudokirchneriella subcapitata were studied. In addition, the effects of mixed extracts on ten taxonomically different freshwater microalgae species, using the single-species and mixed culture species tests were also studied. Among the five different extracts tested chloroform extract and mixed extracts of the two plant species showed the highest anti-algal potential with P. subcapitata. The sensitivity of microalgae species tested in single-species cultures to P. crispus and M. spicatum extracts found to be group-specific, in which cyanophyte Anabaena flos-aquae var. treleasei and the diatoms Gomphoneis eriense var. apiculate and Tryblionella hungarica were more sensitive compared to the tested green microalgae species. In addition, the inhibitory effects of macrophyte extracts decreased for the mixed microalgae cultures. The extracts of P. crispus and M. spicatum showed the presence of some bioactive compounds that could contribute toward the phyto-algicidal properties of these plants.

Influence of a light source on microalgae growth and subsequent anaerobic digestion of harvested biomass

The aim of the study was to determine the influence of the light source on the taxonomic structure and chemical composition of the harvested biomass, and on the fermentative biogas/methane production. Cultivation of a mixed microalgae culture was carried out in closed vertical photobioreactors equipped with different light sources. The effectiveness of anaerobic digestion was analysed by respirometric measurements. The harvested microalgae biomass was characterized by various taxonomic structures and varied chemical composition depending on the light source used during cultivation stage. In variants where warm white LED lighting and red light were used, species from the Cyanoprokaryota division predominated, characterized by a high concentration of organic compounds and nitrogen in the biomass. TOC values amounted to almost 430 mg/g TS. In the remaining variants, Chlorophyta predominated, and TOC values were in the range of 388.0–411.3 mg/g TS. A significantly higher biogas/methane production (p = 0.05) was found in variants in which biomass with Cyanoprokaryota predominating was tested. The biogas yield was in the range of 383.2 L/kg VS to 400.8 L/kg VS, and the methane content was close to 55%. A lower effectiveness of biogas and methane formation were observed in variants with Chlorophyta as a predominating taxonomic group.

Growth comparison of microalgae in tubular photobioreactor and open pond for treating anaerobic digestion piggery effluent

The overwhelming interest in the use of microalgae to handle associated nutrient surge from anaerobic digestion technologies for the treatment of wastewater, is driven by the need for efficient nutrient recovery, greenhouse gas mitigation, wastewater treatment and biomass reuse. Here, the feasibility of growth and ammonium nitrogen removal rate of semi-continuous mixed microalgae culture in paddle wheel-driven raceway pond and helical tubular closed photobioreactor (Biocoil) for treating sand-filtered, undiluted anaerobic digestion piggery effluent (ADPE) was compared under outdoor climatic conditions between June and September 2015 austral winter season. Two Biocoils, (airlift and submersible centrifugal pump driven) were tested. Despite several attempts in using airlift-driven Biocoil (e.g. modification of the sparger design), no net microalgae growth was observed due to intense foaming and loss of culture. Initial ammonium nitrogen concentration in the Biocoil and pond was 893.03±17.0mg NH4+-NL−1. Overall, similar average ammonium nitrogen removal rate in Biocoil (24.6±7.18mg NH4+-NL−1day−1) and raceway pond (25.9±8.6mg NH4+-NL−1day−1) was achieved. The average volumetric biomass productivity of microalgae grown in the Biocoil (25.03±0.24mg AFDW L−1day−1) was 2.1 times higher than in raceway pond. While no significant differences were detected between the cultivation systems, the overall carbohydrate, lipid and protein contents of the consortium averaged 29.17±3.22, 32.79±3.26 and 23.29±2.15% AFDW respectively, revealing its suitability as animal feed or potential biofuel feedstock. The consortium could be maintained in semi-continuous culture for more than three months without changes in the algal composition. Results indicated that microalgae consortium is suitable for simultaneous nutrient removal and biomass production from piggery effluent.

Removal of nutrients and organic pollution load from pulp and paper mill effluent by microalgae in outdoor open pond

A mixed culture of microalgae, containing two Scenedesmus species, was analysed to determine its potential in coupling of pulp and paper mill effluent treatment and microalgal cultivation. Laboratory studies suggested that 60% concentration of wastewater was optimum for microalgal cultivation. A maximum of 82% and 75% removal of BOD and COD respectively was achieved with microalgal cultivation in outdoor open pond. By the end of the cultivation period, 65% removal of NO3-N and 71.29% removal of PO4-P was observed. The fatty acid composition of mixed microalgal culture cultivated with effluent showed the palmitic acid, oleic acid, linoleic acid and α-linolenic acid as major fatty acids. The results obtained suggest that pulp and paper mill effluent could be used effectively for cultivation of microalgae to minimise the freshwater and nutrient requirements.

Stabilizing continuous mixed cultures of microalgae

Microalgae are a promising source of renewable biofuels because they are highly productive, can utilize low quality water, and do not compete with cropland. Recent studies have shown that monocultures are difficult to maintain, but mixed cultures of two or more strains, species or higher taxa may increase and stabilize productivity. Continuous cultures have the potential to support higher long-term average productivity and yields than batch cultures. However, methods are lacking to preclude competitive exclusion and maintain desired mixture composition in long term continuous cultures. First, we grew mixed batch cultures of Dunaliella sp. GSP-980625-1E and the diatom Phaeodactylum tricornutum (CCMP 1327) and found no difference in growth rates or lipid productivity compared to monocultures. Next, we determined the responses (growth rate and photosynthetic efficiency) of those species plus the cyanobacterium Aphanothece sp. CCMP 2529 to four salinity×three nutrient full factorial conditions. Salinity responses were confirmed in single species cycloturbidostat continuous cultures. Finally, we used that information to stabilize mixed continuous cultures of Dunaliella and Aphanothece by alternating salinity to successively favor one or the other species.

The Effect of Salinity on Growth, Dry Weight and Lipid Content of the Mixed Microalgae Culture Isolated from Glagah as Biodiesel Substrate

The Effect of Salinity on Growth, Dry Weight and Lipid Content of the Mixed Microalgae Culture Isolated from Glagah as Biodiesel Substrate

Effect of temperature on ammonium removal in Scenedesmus sp.

The effect of temperature on microalgal ammonium uptake was investigated by carrying out four batch experiments in which a mixed culture of microalgae, composed mainly of Scenedesmus sp., was cultivated under different temperatures within the usual temperature working range in Mediterranean climate (15–34°C). Ammonium removal rates increased with temperature up to 26°C and stabilized thereafter. Ratkowsky and Cardinal temperatures models successfully reproduced the experimental data. Optimum (31.3°C), minimum (8.8°C) and maximum (46.1°C) temperatures for ammonium removal by Scenedesmus sp. under the studied conditions were obtained as model parameters. These temperature-related parameters constitute very useful information for designing and operating wastewater treatment systems using these microalgae.

Surface physicochemical properties of selected single and mixed cultures of microalgae and cyanobacteria and their relationship with sedimentation kinetics

Abstract Background Microalgae are photosynthetic microorganisms presenting a diversity of biotechnological applications. However, microalgal cultivation systems are not energetically and economically feasible. Possible strategies that can be applied to improve the feasibility of microalgal production include biofouling control in photobioreactors, the use of attached growth systems and bioflocculation. These processes are ruled by surface physicochemical properties. Accordingly, the surface physicochemical properties of Chlorella vulgaris, Pseudokirchneriella subcapitata, Synechocystis salina and Microcystis aeruginosa were determined through contact angle and zeta potential measurements. Additionally, mixed cultures of the selected microorganisms were performed. Sedimentation kinetics of the studied cultures was also evaluated to understand how surface physicochemical properties influence microalgal recovery. Results All studied microorganisms, except S. salina, presented a hydrophilic surface. The co-culture of S. salina with the other studied microorganisms resulted in a more hydrophobic algal suspension. Regarding zeta potential determinations, all studied suspensions presented a negatively charged surface (approximately -40.8 ± 4.4 mV). Sedimentation experiments have shown that all microalgal suspensions presented low microalgal recovery efficiencies. However, a negative linear relationship between microalgal removal percentage and free energy of hydrophobic interaction was obtained. Conclusions The evidence of a relationship between microalgal removal percentage and free energy of hydrophobic interaction demonstrates the importance of surface physicochemical properties on microalgal settling. However, the low recovery efficiencies achieved, as well as the high net zeta potential values determined, indicate that another factor to consider in microalgal settling is the ionic strength of the culture medium, which play an important role in suspensions’ stability.

Antimutagenic Properties of Biologically Active Substances of Microalgae Associates.

IntroductionThere are an increasing number of different xenobiotics negatively influencing population health. Therefore, it is important to find effective protectors against mutagenic and toxic effects of environmental pollutants. Naturally occurring biologically active substances, the majority of which are antioxidants, are capable of functioning as modifiers of the induced mutation process. The application of various naturally occurring protectors will lower essential risks of congenital malformations, cancer, and hereditary diseases caused by mutational damages. Therefore, it is crucial to screen algal flora of Kazakhstan for the antimutagenic activity. This study involved the assessment of antimutagenic potential of biologically active polypeptide (BAP) produced in mixed microalgae cultures.Methods70 white outbred male rats (Rattus norvegicus) at 6 months of age were used for this study. The dosage of BAP produced by microalgae associates Anabaena flos-aquae x Anabaenopsis sp. comprised 100 mg/kg. Cadmium sulfate was used as a mutagen in a concentration of 1 mg/kg. Experiments on antimutagenic activity of BAP were carried out with the Mammalian Bone Marrow Chromosomal Aberration Test.ResultsAfter acute and subacute exposure of BAP, the level of chromosomal structural abnormalities in rat bone marrow cells was the same as in control group. Therefore, BAP showed no mutagenic activity, whereas exposure to cadmium sulfate at used concentration induced chromosomal aberrations with a significantly higher frequency than the spontaneous mutation rate. The exposure combination of BAP with cadmium sulfate resulted in a two-fold decrease (p< 0.05) of mutagen-induced chromosomal aberrations. The range of induced chromosomal aberrations included alterations of all types both in control and experimental groups.ConclusionMost of the genotoxic effects are mediated through oxidative stress. The repair of DNA damage is an enzymatic process, which depends on the cellular metabolic rate. It has previously been shown that many biologically active substances lead to reduction of DNA sensitivity to mutagenic damaging factors. Based on these facts and obtained results, it can be assumed that BAP from mixed microalgae cultures Anabaena flos-aquae x Anabaenopsis sp. are capable of blocking free radical process reducing the likelihood of genome damage, as well as triggering the cellular repair system.

Mixed microalgae culture for ammonium removal in the absence of phosphorus: Effect of phosphorus supplementation and process modeling

Microalgal growth and ammonium removal in a P-free medium have been studied in two batch photobioreactors seeded with a mixed microalgal culture and operated for 46 days. A significant amount of ammonium (106mg NH4-Nl−1) was removed in a P-free medium, showing that microalgal growth and phosphorus uptake are independent processes. The ammonium removal rate decreased during the experiment, partly due to a decrease in the cellular phosphorus content. After a single phosphate addition in the medium of one of the reactors, intracellular phosphorus content of the corresponding microalgal culture rapidly increased, and so did the ammonium removal rate. These results show how the amount of phosphorus internally stored affects the ammonium removal rate. A mathematical model was proposed to reproduce these observations. The kinetic expression for microalgae growth includes a Monod term and a Hill's function to represent the effect of ammonium and stored polyphosphate concentrations, respectively. The proposed model accurately reproduced the experimental data (r=0.952, P-value <0.01).

Comparison of pretreatment methods for total lipids extraction from mixed microalgae

Cell disruption can increase the extraction efficiency of total lipids from microalgae for further conversion to biodiesel. Four different pretreatment methods were tested on mixed cultures of microalgae harvested in a stabilization pond system treating sewage: ultrasonication (US), microwaving (MW), autoclave (AC) and electroflotation by alternating current (EFAC). The best results in terms of total lipid yield were: MW (33.7 ± 5.3%), followed by EFAC (24.8 ± 7.1%), AC (15.4 ± 2.3%), and US (13.3 ± 3.0%). However, when both efficiency and costs are considered, EFAC gave the best result and can be an excellent option for simultaneous microalgae harvesting and cell disruption.

Population dynamics in mixed cultures of Neochloris oleoabundans and native microalgae from water of a polluted river and isolation of a diatom consortium for the production of lipid rich biomass

The production of biodiesel utilizing microalgae has driven innovation worldwide, especially trying to overcome the current economic and technological limitations of the whole process. Within these efforts, the use of wastewater to cultivate oleaginous microalgae or the use of dual-purpose microalgae-bacteria-based systems that treat wastewater and produce oleaginous microalgae have become an attractive alternative. The aim of this work was to evaluate the population dynamics which occurred in mixed cultures of Neochloris oleoabundans with other native microalgae, in mixtures of a synthetic medium (BBM) and water of an urban polluted river. The effect of temperature, nutrient availability and the microscopic monitoring of the population dynamics in such mixed cultures were carried out. Furthermore, the isolation of the predominant consortium of diatoms and the evaluation of its kinetics of growth and its capacity for removal of pollutants was also performed. Results indicated that such green microalgae only predominated in mixtures containing 80% or 60% of the synthetic medium. In mixtures containing a volume of the polluted river higher than 40%, other microalgae predominated, especially diatoms of various genera. The diatom consortium isolated from a 100% of the river's water sampled in spring (April), was formed mainly by a population of Nitzchia frustulum and in less extent of Navicula sp. It showed a significantly higher specific growth rate when cultivated in water from the river, compared to cultures in synthetic modified diatom medium (MDM) and at 32°C, compared to cultures incubated at 25°C. The consortium was able to remove 95.45% and 95.78% of ammonia nitrogen, 60% and 62.5% of nitrates at 32°C and 25°C, respectively, after 2 days. It also removed 95% of phosphates at 32°C and 67% at 25°C after 4 days from the polluted river. Diatoms also showed significant accumulation of lipids after 10 days of cultivation when stained with Sudan III. In conclusion, such diatom consortium showed a large potential for being used in a dual-purpose system that could treat the water from polluted streams and that could produce lipid rich biomass.

The stabilisation potential of individual and mixed assemblages of natural bacteria and microalgae.

It is recognized that microorganisms inhabiting natural sediments significantly mediate the erosive response of the bed (“ecosystem engineers”) through the secretion of naturally adhesive organic material (EPS: extracellular polymeric substances). However, little is known about the individual engineering capability of the main biofilm components (heterotrophic bacteria and autotrophic microalgae) in terms of their individual contribution to the EPS pool and their relative functional contribution to substratum stabilisation. This paper investigates the engineering effects on a non-cohesive test bed as the surface was colonised by natural benthic assemblages (prokaryotic, eukaryotic and mixed cultures) of bacteria and microalgae. MagPI (Magnetic Particle Induction) and CSM (Cohesive Strength Meter) respectively determined the adhesive capacity and the cohesive strength of the culture surface. Stabilisation was significantly higher for the bacterial assemblages (up to a factor of 2) than for axenic microalgal assemblages. The EPS concentration and the EPS composition (carbohydrates and proteins) were both important in determining stabilisation. The peak of engineering effect was significantly greater in the mixed assemblage as compared to the bacterial (x 1.2) and axenic diatom (x 1.7) cultures. The possibility of synergistic effects between the bacterial and algal cultures in terms of stability was examined and rejected although the concentration of EPS did show a synergistic elevation in mixed culture. The rapid development and overall stabilisation potential of the various assemblages was impressive (x 7.5 and ×9.5, for MagPI and CSM, respectively, as compared to controls). We confirmed the important role of heterotrophic bacteria in “biostabilisation” and highlighted the interactions between autotrophic and heterotrophic biofilm consortia. This information contributes to the conceptual understanding of the microbial sediment engineering that represents an important ecosystem function and service in aquatic habitats.

Marine Biosurfactants, III. Toxicity Testing with Marine Microorganisms and Comparison with Synthetic Surfactants

Eight synthetic and nine biogenetic surfactants were tested on their toxicity. Because of their possible application as oil dispersants against oil slicks on sea, the test organisms used were marine microorganisms (mixed and pure cultures of bacteria, microalgae, and protozoa). Bacterial growth was hardly effected or stimulated, whilst that of algae and flagellates was reduced. All substances tested were biodegraded in sea water. The bioluminescence of Photobacter phosphoreum (Microtox test) was the most sensitive test system used. A ranking shows that most biogenetic surfactants were less toxic than synthetic surfactants. No toxicity could be detected with the glucose-lipid GL, produced by the marine bacterium Alcaligenes sp. MM1.

Influence of different lights of mixed cultures of microalgae from ancient frescoes

Deterioration of frescoes inside a hypogean room of the Domus aurea in Rome was mainly caused by the growth of an algal association which persisted on the frescoes even in darkness. Following the proposal to utilize a new illumination system, the present research was undertaken to ascertain the effect of an incandescent lamp on the whole association in culture. For comparison a fluorescent lamp was also employed, and two low light intensities were tested. Observations on the development and morphology of the various algal species and analysis of the photosynthetic pigment content indicate that the Lyngbya spp. dominant in the association appeared to be highly adaptable to both lamps and intensities. Carefully limited use of the new lamp was advisable.