Photofermentative hydrogen production by immobilized Rhodopseudomonas sp. S16-VOGS3 cells in photobioreactors

One of the most important solutions to overcome energy and environmental problems and to replace the fossil fuel-based economy could be the use of photosynthetic microorganisms.The use of photosynthetic microorganisms is a potential alternative to energy generation from fossil fuels because they efficiently produce hydrogen(H_(2)).Immobilization of photosynthetic microorganisms is used for many biotechnological applications such as H_(2) production.This method appears attractive because it restricts cell movement in an entrapped matrix.Immobilization of Rhodopseudomonas sp.S16-VOGS3 cells is a promising way to improve H_(2) production.In this work,the ability of immobilized Rhodopseudomonas sp.S16-VOGS3 cells to produce H_(2) was investigated in two types of PBRs.The PBRs used in this work were a cylindrical one with 0.2 L working volume(C-PBR)and a flat Roux type with 0.6 L working volume(FRT-PBR).The calcium alginate beads prepared were resistant to culture mixing and showed little leakage of cells,and the immobilized cells continued the photofermentation process in both PBRs.The immobilized cells in the C-PBR produced 936.8 mL of H_(2) with an average H_(2) production rate of 2.99 mL/h.The average productivity was 126.4μL(H_(2))/mg(cells)/h or 14.96 mL(H_(2))/L(culture)/h,and the light conversion efficiency was 2.37%.The immobilized cells in the FRT-PBR produced a total of 662.2 mL of H_(2) with an average H_(2) production rate of 1.55 mL/h.The average productivity was 31.1μL(H_(2))/mg(cells)/h or 2.58 mL(H_(2))/L(culture)/h,and the light conversion efficiency was 0.52%.The more uniform and therefore more efficient degree of bacterial cell mixing achieved in the C-PBR with cylindrical configuration played an important role compared to the FRT-PBR.In the FRT-PBR,the beads were aggregated at the bottom,which limited light penetration and resulted in low H_(2) production efficiency.

Progress in microalgae cultivation photobioreactors and applications in wastewater treatment:A review

Using microalgae to treat wastewater has received growing attention in the world because it is regarded as a novel means for wastewater treatment.It is commonly recognized that large-scale cultivation and commercial application of microalgae are limited by the development of photobioreactor(PBR).Although there are a lot of PBRs for microalgae pure cultivation which used culture medium,specialized PBRs designed for wastewater treatment are rare.The composition of wastewater is quite complicated;this might cause a very different photosynthetic effect of microalgae compared to those grown in a pure cultivation medium.Therefore,PBRs for wastewater treatment need to be redesigned and improved based on the existing PBRs that are used for microalgae pure cultivation.In this review,different PBRs for microalgae cultivation and wastewater treatment are summarized.PBR configurations,PBR design parameters and types of wastewater are presented.In addition,the wastewater treatment efficiency and biomass productivity were also compared among each type of PBRs.Moreover,some other promising PBRs are introduced in this review,and a two-stage cultivation mode which combines both closed and open system is discussed as well.Ultimately,this article focuses on current problems and gives an outlook for this field,aiming at providing a primary reference for microalgae cultivation by using wastewater.

Cultivation of Microalgae <i>Monoraphidium</i>sp., in the Plant Pilot the Grand Valle Bio Energy, for Biodiesel Production

At present, Brazil imports approximately 11 billion liters/year of diesel. With the interruption of the works in the new Petrobras refineries, the projection is that by 2025 this volume will increase to 24.2 billion liters of diesel/year. In this sense, the biodiesel factory Grand Valle Bio Energy Ltda., located in the state of Rio de Janeiro, in conjunction with the FAPERJ makes some investments in technology development for the cultivation and use of microalgae as an alternative raw material in the production of biodiesel. Based on arguments previously said, this work presents the results of the microalgae cultivation Monoraphidium sp. in photobioreactors the pilot plant of the company. The installation with an area of 120 m2 is included with 2 open photobioreactors of type falling film (20 m × 1 m), with a cascade of 18mm and capacity of 4000 L. The lineage cultivated is selected from previous ecophysiological studies that are identified as promising for biodiesel production by having a high potential for the production of lipids. This lineage is maintained at collection of the stock of cultures Laboratory of Green Technologies of the School of Chemistry/ UFRJ. The cultivation was performed in means ASM-1 (Gorham et al., 1964), initial pH 8.0, with aeration and circulation average of 8 hours a day during 19 days. The culture was started with an inoculum of 1 × 107 cel/ml. The lipid production was determined in two phases of growth: on day 4 (exponential phase) and 15 day (stationary phase). For the determination and quantification of lipid content, two different methods were assessed for a sample of biomass, submitted to the same processes the separation and drying. The results showed the methodology of Bligh & Dyer with modifications as the most efficient in extracting lipids. The total lipid content of the biomass Monoraphidium sp. was 30.58%. The growth rate varied between 0.74 ± 0.01 and 0.68 ± 0.02.

Enhanced removal of nitrate and phosphate from wastewater by Chlorella vulgaris: Multi-objective optimization and CFD simulation

To enhance the efficiency of wastewater biotreatment with microalgae, the effects of physical parameters need to be investigated and optimized. In this regard, the individual and interactive effects of temperature, p H and aeration rate on the performance of biological removal of nitrate and phosphate by Chlorella vulgaris were studied by response surface methodology(RSM). Furthermore, a multi-objective optimization technique was applied to the response equations to simultaneously find optimal combinations of input parameters capable of removing the highest possible amount of nitrate and phosphate. The optimal calculated values were temperature of 26.3 °C, pH of 8 and aeration rate of 4.7 L·min^(-1). Interestingly, under the optimum condition, approximately 85% of total nitrate and 77% of whole phosphate were removed after 48 h and 24 h, respectively, which were in excellent agreement with the predicted values. Finally, the effect of baffle on mixing performance and, as a result, on bioremoval efficiency was investigated in Stirred Tank Photobioreactor(STP) by means of Computational Fluid Dynamics(CFD). Flow behavior indicated substantial enhancement in mixing performance when the baffle was inserted into the tank. Obtained simulation results were validated experimentally. Under the optimum condition, due to proper mixing in baffled STP, nitrate and phosphate removal increased up to 93% and 86%,respectively, compared to unbaffled one.

Design of a Novel Photobioreactor for Culture of Microalgae

This paper presents the design of a novel photobioreactor for cultivation of microalgae. The body of the reactor with volume of about 40 L is parallelipipedic and divided in five compartments that can be put in series. The optical guides, plunged perpendicularly into the compartments, are upright Plexiglas plates on which side faces there are able to diffuse light laterally and ensure an even distribution of light in the medium. External airlifts through the side columns are used for mixing of culture medium. The external light source is a SON-T lamp mounted inside a projector that provides a conical light dispersion, it is interchangeable and may take different positions. The design offers the photobioreactor characteristics including mainly interchangeable light source, homogenous distribution of light, perfect mixing of suspension of algae, high ratio of illuminating surface to volume of reactor, compactness and absence of contamination. Schemes, view of the photobioractor and data of continuous culture forSpirulina maxima are presented.

Microalgae Cultivation Using Offshore Membrane Enclosures for Growing Algae (OMEGA)

OMEGA is a system for cultivating microalgae using wastewater contained in floating photobioreactors (PBRs) deployed in marine environments and thereby eliminating competition with agriculture for water, fertilizer, and land. The offshore placement in protected bays near coastal cities co-locates OMEGA with wastewater outfalls and sources of CO2-rich flue gas on shore. To evaluate the feasibility of OMEGA, microalgae were grown on secondary-treated wastewater supplemented with simulated flue gas (8.5% CO2 V/V) in a 110-liter prototype system tested using a seawater tank. The flow-through system consisted of tubular PBRs made of transparent linear low-density polyethylene, a gas exchange and harvesting column (GEHC), two pumps, and an instrumentation and control (I&C) system. The PBRs contained regularly spaced swirl vanes to create helical flow and mixing for the circulating culture. About 5% of the culture volume was continuously diverted through the GEHC to manage dissolved oxygen concentrations, provide supplemental CO2, harvest microalgae from a settling chamber, and add fresh wastewater to replenish nutrients. The I&C system controlled CO2 injection and recorded dissolved oxygen levels, totalized CO2 flow, temperature, circulation rates, photosynthetic active radiation (PAR), and the photosynthetic efficiency as determined by fast repetition rate fluorometry. In two experimental trials, totaling 23 days in April and May 2012, microalgae productivity averaged 14.1 ± 1.3 grams of dry biomass per square meter of PBR surface area per day (n = 16), supplemental CO2 was converted to biomass with >50% efficiency, and >90% of the ammonia-nitrogen was recovered from secondary effluent. If OMEGA can be optimized for energy efficiency and scaled up economically, it has the potential to contribute significantly to biofuels production and wastewater treatment.

SPIRULINA CULTIVATION IN CHINA

This paper reviews and discusses the development and many problems of Spirulinacultivation in China, points out the advantages and disadvantages of open photobioreactor system, andpredicts that seawater Spirulina cultivation will be a new trend to be strengthened and emphasized due toits special physiological characteristics, easier managment, lower fertilizer cost, and higher resistance tocontaminants and rare pollution of chemicals.

H_2 PRODUCTION BY ANABAENA VARIABILIS MUTANT IN COMPUTER CONTROLLED TWO-STAGE AIR-LIFT TUBULAR PHOTOBIOREACTOR

A 4.34 liter two stage air lift photobioreactor incorporating Anabaena variabilis ATCC29413 mutant PK84 was used to study H 2 production. Results showed that H 2 production increased with increasing light intensity from 47 μE/(m 2·s) up to 190 μE/(m 2·s), but that further increase of light intensity decreased the H 2 production because of the inhibition due to the high pO 2. The data also indicated that longer argon gas charge resulted in more H 2 produced due to the increase of nitrogenase activities and heterocyst frequency, and that more than 1.3 L net H 2 was produced from this computer controlled photobioreactor.

Split internal-loop photobioreactor for Scenedesmus sp.microalgae:Culturing and hydrodynamics

In this study,the evaluation of the performance of the split internal loop photobioreactor for culturing a species of green microalgae,Scenedesmus sp.under different operating superficial gas velocity and during a different time of growth(i.e.,starting for the first day until end day of the culturing process)was addressed.The evaluation of the performance of the split internal loop photobioreactor was included assessing the density,pH,temperature,viscosity,surface tension,the optical density,cell population,dry biomass,and chlorophyll of the culture medium of the microalgae culturing.Additionally,the hydrodynamics of a Split Internal-Loop Photobioreactor with microalgae culturing was comprehensively quantified.Radioactive particle tracking(RPT)and gamma-ray computed tomography(CT)techniques were applied for the first time to quantify and address the influence of microalgae culture on the hydrodynamic parameters.The hydrodynamics parameters such as local liquid velocity field,shear stresses,turbulent kinetic energy,and local gas holdup profiles were measured at different superficial gas velocities as well as under different times of algae growth.The obtained results indicate that the flow distribution may significantly affect the performance of the photobioreactor,which may have substantial effects on the cultivation process.The obtained experimental data can serve as benchmark data for the evaluation and validation of computational fluid dynamics(CFD)codes and their closures.This,in turn,allows us to develop efficient reactors and consequently improving the productivity and selectivity of these photobioreactors.

HYDROGEN PHOTOPRODUCTION OF A.VARIABILIS INCORPORATED IN A PHOTOBIOREACTOR

H2 photoproduction and nitrogenase activities in two strains of Anabaena variabilismarked wild type ATCC 29413 and mutant PK84 exposed to thermal stress (temperature higher than thenormal incubation temperature of 30℃) were studied. Cultures of both strains collected from any intervalof logarithmic growth phase exhibited high H2 photoproduction and nitrogenase activities when exposed tolimited time heat shock during the assay process. In contrast, the algal H2 photoproduction rate of bothstrains fluctuated with long term thermal stress caused hy increasing the growth temperature from 30℃ to36℃.The changes of nitrogenase (the key H2 photobiosynhetic enzyme) activities in the mutant PK84showed variation tendency similar to that of H2 photoproduction during exposure to thermal stress, indicat-ing that fluctuation of H2 photopnduction in the mutant was mainly due to the variation of nitrogenase ac-tivities. A temporary maximal H2 photoproduction in the mutant PK84 (wild type ATCC29413 ) was ob-served when cells po at 36℃ for 14 (6) days. However, the responses of nitrogenase activities in thewild type to thermal stress were not completely similar to those in the mutant in spite of similar variationsof H2 photoproduction in both strains. The data obtained in these studies suggested tha the activities ofother enzymes (in the wild strain) involved in H2 photoproduction were affected by thermal stress since H2photoporduction maximized or dropped to 0 without variation tendency similar to that of nitrogenase activi-ties.Furthermore, an enhancement of H2 photoproduction speed of the mutant strain cultured in a 4.4 Llaboratory photobioreactor was also observed when it was subjected to short time continuous charge of ar-gon, and temperature rise.All these results indicated that high temperature plays an important role in the photo-autotrophic H2photoproduction, and that long term thermal stress is unfavourable for net H2 phooproduction in bothstrains of A. variabilis though short-time heat shock is conducive to H2 photoproduction.

Photobioreactor of Microalgas for CO_(2) Biofixation

Microalgae are unicellular organisms capable of photosynthesis, turning sunlight and carbon dioxide (CO2) into rich biomass. Precisely because of this definition, in recent years various sectors have been targeting their ability to reduce CO2 emissions and the capacity of simultaneously synthesize biomass which can be later used to produce bio-fuels. Besides being considered fast-growth microorganisms, microalgae have a diverse biochemical composition with similar characteristics to traditional biomass. In this context, the present work aimed to evaluate the biofixation of CO2 by the microalgae Monoraphidium sp., cultivated in a closed-window type photobioreactor, as well as characterization of microalgal biomass produced in relation to the total lipid content (TL), lipids converted into biodiesel (LCB), carbohydrates and proteins. The results achieved showed that the best result was obtained after 24 h of cultivation, where for each gram of biomass produced approximately 1.2 g of CO2 were consumed. In the growth phase the average biomass productivity in the Janela photobioreactor was 58 mg&middot;L-1&middot;day-1 concluding that microalgae culture systems could be coupled to the chimneys of large industries emitters CO2 using this gas, resulting from combustion processes, in the process of photosynthesis. The biomass Monoraphidium sp. produced had a content of lipids converted into biodiesel of approximately 8.36% ± 2.69%, carbohydrates 32% ± 3.37% and proteins 34.26% ± 0.41%.

The Growth Factors Involved in Microalgae Cultivation for Biofuel Production: A Review

The growing demand for energy and the negative environmental impacts of fossil fuel use are triggering global searches for a renewable and eco-friendly alternative biofuel. Microalgae are considered as one of the most promising feedstocks for biofuel production, due to many advantages including cultivation in non-arable land and being able to grow in wastewater or seawater. That is why;microalgae-based biofuels are regarded as one of the best candidates to replace fossil fuels. There are two main types of microalgae cultivation systems: Open Raceway Ponds and Closed Photobioreactos (PBRs). Due to some limitations in Open Raceways, PBRs have become the most favorable choice for biofuel producers, even though it is costly. To make the process viable, the growth of microalgae for biofuel production should be cost-effective. One way to achieve this goal is to optimize the environmental factors that influence their growth during the cultivation stage to increase the accumulation of bio-compounds of fuel. Algal growth relies mostly on nutrients, CO2 concentration, pH and salinity, light intensity and quality, temperature and finally mixing, which directly affects all other factors. Thus, before designing PBR, a thorough study on these growth parameters is needed. In the present study, we reviewed and evaluated these growth influencing factors in an extensive way to optimize biofuel production.

Improvement of Medium Composition and Utilization of Mixotrophic Cultivation for Green and Blue Green Microalgae towards Biodiesel Production

A possible source of biological material for the production of biodiesel is represented by microalgae, in particular by their lipid content. The aim of the present work was to optimize culture medium composition for improving growth and lipid content of green microalgae Chlorella sorokiniana, Scenedesmus acuminatus and blue green Cyanobacterium aponicum. Lipids were quantitatively determined by spectrofluorometric method using Nile red flurometric stain. Initially, the effect of two different medium types, Bold’s and optimized culture medium (OCM), four types of carbon source (glucose and sodium acetate, molasses, glycerol, control) and four nitrogen concentrations (100%, -75%, -50%, -25%) on the enhancement of biomass and lipid content and lipid productivity were studied;indeed, optimized culture medium significantly improved growth, CDW for three microalgae, beside increasing lipid content and lipid productivity for S. acuminatus and C. aponicum by 7.5 and 5 folds respectively at 25th day compared to Bold’s medium. Moreover, 25% nitrogen deficient medium significantly increased lipid content and lipid productivity for both C. sorokiniana and C. aponicum at 2nd week of re-propagation to 10.6 and 2.6 folds over control (100% nitrogen). While S. acuminatus recorded the significant lipid content & productivity at 2nd week under recommended nitrogen dose in medium (100% N) by 4.4 folds over 25% deficient medium. Meanwhile 0.3% glycerol medium enhanced CDW, lipid content of S. acuminatus to 1.68 gL-1. While C. sorokiniana and C. aponicum recorded significant CDW under 0.3% acetate medium 1.37 and 0.76 gL-1. C. aponicum exhibited no growth under glycerol medium. The highest lipid content and lipid productivity were obtained under glycerol medium for C. sorokiniana and S. acuminatus (64.3 and 52.8 mg·g·g&#451·d&#451).

Biosynthesis of ^(13)C-Labeled Amino Acids and Sugars by Spirulina (Arthrospira) Maxima in a Parallelepiped Photobioreactor

This paper presents the investigation on biosynthesis of high-value-added amino acids and sugars labeled uniformly with stable isotope 13C by microalga Spirulina (Arthrospira) maxima in a parallelepiped photobioreactor. The kinetic data of both batch and continuous cultures with characterization of the amino acids and sugars are shown. The continuous culture without nutrients deficiency is for biosynthesis of amino acids, with tyrosine as one of the principal constituents, and the batch culture with deficiency in nitrogen is for biosynthesis of labeled glucose that is up to 64% versus dry mass of cells.

Review of the biological and engineering aspects of algae to fuels approach

Current biofuel production relies on limited arable lands on the earth,and is impossible to meet the biofuel demands.Oil producing algae are alternative biofuel feedstock with potential to meet the world’s ambitious goal to replace fossil fuels.This review provides an overview of the biological and engineering aspects in the production and processing technologies and recent advances in research and development in the algae to fuels approach.The article covers biology,selection and genetic modification of algae species and strains,production systems design,culture media and light management,harvest and dewatering,downstream processing,and environment and economic assessment.Despite the many advances made over several decades,commercialization of algal fuels remains challenging chiefly because of the techno-economic constraints.Technological breakthroughs in all major aspects must take place before commercial production of algal fuels becomes economically viable.

Improvement of microalgae lipid productivity and quality in an ion-exchange-membrane photobioreactor using real municipal wastewater

To improve the productivity and quality of microalgae-based biodiesel when using municipal wastewater(MW)as nutrients source,an ion-exchange-membrane photobioreactor(IEM-PBR)was used in this study to eliminate the negative effects of pollutants in MW on microalgae Chlorella vulgaris and Scenedesmus obliquus.In the IEM-PBR,the real MW and microalgae cultures were separated in two chambers by the ion-exchange-membranes(IEMs).Nutrients(N,P,etc.)in the MW permeated into microalgae cultures through the IEMs,while pollutants(suspended solids,competitors,etc.)in the MW could hardly permeate into microalgae cultures.As a result,the lipid productivity in the IEM-PBR was improved to 85.7 mg/(L·d)for C.vulgaris and 111.8 mg/(L·d)for S.obliquus,which was slightly higher than that in the traditional photobioreactor(T-PBR)with real MW after centrifugation(82.5 mg/(L·d)for C.vulgaris and 105.8 mg/(L·d)for S.obliquus),but much higher than that in the T-PBR with untreated MW and primary MW(with lipid productivity of 20-30 mg/(L·d)).Besides,the lipid quality obtained in the IEM-PBR had higher proportion of cetane number(ca.60%)and lower linolenic acid content(ca.8%),which showed a superior quality in the IEM-PBR to that in the T-PBR.It demonstrated that the IEM-PBR is an effective approach to improve the productivity and quality of microalgae biodiesel.

Optical extinction characteristics of three biofuel producing microalgae determined by an improved transmission method

The optical extinction characteristics of the three kinds of microalgae Nannochloropsis maritirna, Ellip- soidion sp. （277.03）, and Dunaliella tertiolecta were determined using an improved transmission method, in the 300-1800 nm spectral range. These three microalgae are promising candidates for the production of biofuels such as bio-hydrogen and biodiesel. The improved transmission method determines the spec- tral extinction coefficient of the microalgae. This is based on the measured transmittance, and employs an optical model that takes into consideration multiple reflections and refractions at the air-glass and glass-liquid interfaces. Silicon dioxide microspheres of monodisperse size were used as a model to verify the proposed method. The optical constants of the culture medium, size distributions, and extinction cross-sections of the microalgae cells were measured and analyzed. The improved transmission method is demonstrated to yield more accurate results than the traditional method. The spectral extinction effi- ciencies of the three kinds of microalgae show significant differences in the near ultraviolet and visible spectral regions. The spectral extinction efficiencies also exhibit small differences in the longer wave- length range of 950-1800 rim, with values generally less than 1.0. The measured extinction characteristics data of the three microalgae and the presented measurement method will facilitate process modeling in ohotobioreactors for biofuel oroduction.

Carbon dioxide fixation by Chlorella sp.USTB-01 with a fermentor-helical combined photobioreactor

A promising microalgal strain isolated from fresh water,which can grow both autotrophically on inorganic carbon under lighting and heterotrophically on organic carbon without lighting,was identified as Chlorella sp.USTB-01 with the phylogenetic analysis based on 18S ribosomal ribonucleic acid(rRNA)gene sequences.In the heterotrophic batch culture,more than 20.0 g·L^(-1)of cell dry weight concentration(DWC)of Chlorella sp.USTB-01 was obtained at day 5,and which was used directly to seed the autotrophic culture.A novel fermentor-helical combined photobioreactor was established and used to cultivate Chlorella sp.USTB-01 for the fixation of carbon dioxide(CO_(2)).It showed that the autotrophic growth of Chlorella sp.USTB-01 in the combined photobioreactor was more effective than that in the fermentor alone and the maximum DWC of 2.5 g·L^(-1)was obtained at day 6.The highest CO_(2)fixation of 95%appeared on day 1 in the exponential growth phases of Chlorella sp.USTB-01 and 49.8%protein was found in the harvested microalgal cells.

Innovative design for a portable hybrid system of hydroponic and microalgae to produce food and biofuels

This study investigates an innovative hybrid system that combines hydroponics and microalgae in a compact portable shipping container.This container is divided into two parts;one contains the microalgae system and the other contains the hydroponic system.This combined system works by dividing the 24 hours into 12 hours of light and 12 hours of dark for each part.Both parts are connected using light-impermeable pipes that pass carbon dioxide from the dark side to the lit side and oxygen from the lit side to the dark side.In this paper,the authors developed a validated mathematical model for hydroponic and microalgae to evaluate the system’s performance.Results found by the model show the optimum parameters for the split photobioreactor and hydroponic system.The first investigated parameter is the sparger diameter for split the photobioreactor and the second is the number of plants that give the better and optimum result.The optimum modelling design for the combined hydroponic and microalgae system was using 100 plants for lettuce and three photobioreactors with a 0.009-m diameter for sparger to a photobioreactor system with an area of 15.6 m^(2).

Applicability of differential fluorescein diacetate and propidium iodide fluorescence staining for monitoring algal growth and viability

Microalgae can be cultivated for producing high-valued products through the production of enzymes to offset the cost of CO_(2) sequestration,providing financial incentives.The viability of algae in the photobioreactor needs to be monitored to ensure biologically active live cells.In this study,we explored a simple fluorometry method for differentiation of live and dead algal cells in photobioreactors by fluorescein diacetate(FDA)and propidium iodide(PI)fluorescence staining.FDA stains fluorescent green to the living cells while PI stains the dead cells,allowing the discrimination of live and dead cells.The method was evaluated using two green algae and two strains of cyanobacteria grown in shake flasks and a continuously stirred photobioreactor.The method was found applicable for Chlorella pyrenoidosa and Synechococcus 7002 but was not applicable for the cultures of Scenedesmus dimorphus and Synechococcus elongatus 7942.We conclude that FDA is a good stain for monitoring live algal cells in photobioreactors but its applicability to individual species of algae must be evaluated.