Efficient Biomass Production Research Articles

Artificial intelligence driven process optimization for cleaner production of biomass with co-valorization of wastewater and flue gas in an algal biorefinery

In the present study, an optimized process involving integrated events of flue gas CO2 sequestration and wastewater utilization was developed for improved microalgal biomass production in a cleaner fashion. An artificial neural network (ANN) combined with genetic algorithm (GA) optimization tool was employed for predicting optimal process conditions for enhancing the biomass of the green microalga, Scenedesmus sp., using domestic wastewater as culture medium and coal-fired flue gas as carbon source in an integrated process chain. A 24 central composite design involving four independent process parameters such as light intensity, photoperiod, temperature and initial pH as input variables with biomass productivity as the output was used to construct a non-linear ANN model followed by GA tool to predict optimal combinations of process conditions. Among the tested neural network architecture, 4-12-1 ANN topology was found to be the optimal network architecture in terms of maximum correlation coefficient (R = 0.9947) and minimum mean square error as the performance indexes. On employing the optimized ANN model as fitness function in GA tool, the optimum values of the process parameters for efficient biomass production were as follows: light intensity = 124 μmol m−2 s−1, photoperiod; L:D = 17:7 (h), temperature = 27.5 °C and initial pH = 9.5. These parameters improved the algal biomass productivity by about 57%, CO2 sequestration rate of 578.1 ± 23.1 mg L−1 d−1 and chemical oxygen demand (COD) reduction of 95.9 ± 2.4% were achieved. The optimized process yielded biomass with lipid content and productivity of 34.6% and 106.4 mg L−1 d−1 respectively. The biofuel assessment from the fatty acid methyl ester profile obtained also conformed to the international standard specifications for biodiesel.

Biomass Production and Nutrient Removal by Chlorella vulgaris from Anaerobic Digestion Effluents

One of the most important factors determining the profitability of microalgae biomass production is the use of inexpensive and available source of nutrients. The aim of the study was to determine the possibility of using anaerobic digestion effluents (ADE) from the fermentation of distillery stillage, maize silage and bovine slurry as a nutrient in the production of microalgae Chlorella vulgaris biomass. The highest biomass production of 2319 mg TS/dm3 was obtained during the cultivation of microalgae in the medium consisting of the effluents originating from the fermentation with a high share of bovine slurry. Significantly lower Chlorella vulgaris biomass growth was noted during cultivation in the medium composed of effluents obtained after dewatering of anaerobic sludge from the methane fermentation reactor fed with distillery stillage. In these series, an increase of the initial concentration of N-NH4 in the medium to a level of 160 mg/dm3 significantly reduced microalgae growth. The high efficiency of P-PO4 removal from 87–100% was noted. The study proved that anaerobic digestion effluents might be used as a nutrient source for efficient biomass production of Chlorella vulgaris after optimization of ammonium nitrogen dose.

Maximization of Astaxanthin Production from Green Microalga <i>Haematococcus pluvialis</i> Using Internally-Illuminated Photobioreactor

An internally-illuminated photobioreactor was designed to maximize the astaxanthin production by Haematococcus pluvialis . Four optimization steps were conducted: 1. light wavelength 2. light intensity 3. astaxanthin formation and 4. astaxanthin extraction methods. Efficient biomass production of H. pluvialis of 4.58 ± 0.15 × 10 5 cells/ml and dry biomass of 520 ± 12.5 mg/L was accomplished under red LED light (660 nm) with 70 μmol m -2 s -1 . Besides, the biomass production can be optimized to 5.31 ± 0.15 × 10 5 cells/ml and dry biomass of 680 ± 10.5 mg/L under 140 μmol m -2 s -1 in the light intensity of 70-210 μmol m-2 s-1. Furthermore, the astaxanthin accumulation was significant with 7 days encystment under 140 μmol m -2 s -1 blue LED lights. For extraction method, using hydrochloric acid could obtain the highest astaxanthin yield of 3.85 ± 0.05% (% to dry weight). Further studies were proposed whatever such photobioreactor can be applied to different microalgal strains.

Reconstruction of chromosome rearrangements between the two most ancestral duckweed species Spirodela polyrhiza and S. intermedia.

The monophyletic duckweeds comprising five genera within the monocot order Alismatales are neotenic, free-floating, aquatic organisms with fast vegetative propagation. Some species are considered for efficient biomass production, for life stock feeding, and for (simultaneous) wastewater phytoremediation. The ancestral genus Spirodela consists of only two species, Spirodela polyrhiza and Spirodela intermedia, both with a similar small genome (~160Mbp/1C). Reference genome drafts and a physical map of 96 BACs on the 20 chromosome pairs of S. polyrhiza strain 7498 are available and provide useful tools for further evolutionary studies within and between duckweed genera. Here we applied sequential comparative multicolor fluorescence in situ hybridization (mcFISH) to address homeologous chromosomes in S. intermedia (2n=36), to detect chromosome rearrangements between both species and to elucidate the mechanisms which may have led to the chromosome number alteration after their evolutionary separation. Ten chromosome pairs proved to be conserved between S. polyrhiza and S. intermedia, the remaining ones experienced, depending on the assumed direction of evolution, translocations, inversion, and fissions, respectively. These results represent a first step to unravel karyotype evolution among duckweeds and are anchor points for future genome assembly of S. intermedia.

A critical analysis of species selection and high vs. low-input silviculture on establishment success and early productivity of model short-rotation wood-energy cropping systems

Most research on bioenergy short rotation woody crops (SRWC) has been dedicated to the genera Populus and Salix. These species generally require relatively high-input culture, including intensive weed competition control, which increases costs and environmental externalities. Widespread native early successional species, characterized by high productivity and good coppicing ability, may be better adapted to local environmental stresses and therefore could offer alternative low-input bioenergy production systems. To test this concept, we established a three-year experiment comparing a widely-used hybrid poplar (Populus nigra × P. maximowiczii, clone ‘NM6’) to two native species, American sycamore (Platanus occidentalis L.) and tuliptree (Liriodendron tulipifera L.) grown under contrasting weed and pest control at a coastal plain site in eastern North Carolina, USA. Mean cumulative aboveground wood production was significantly greater in sycamore, with yields of 46.6 Mg ha−1 under high-inputs and 32.7 Mg ha−1 under low-input culture, which rivaled the high-input NM6 yield of 32.9 Mg ha−1. NM6 under low-input management provided noncompetitive yield of 6.2 Mg ha−1. Sycamore also showed superiority in survival, biomass increment, weed resistance, treatment convergence, and within-stand uniformity. All are important characteristics for a bioenergy feedstock crop species, leading to reliable establishment and efficient biomass production. Poor performance in all traits was found for tuliptree, with a maximum yield of 1.2 Mg ha−1, suggesting this native species is a poor choice for SRWC. We conclude that careful species selection beyond the conventionally used genera may enhance reliability and decrease negative environmental impacts of the bioenergy biomass production sector.

English

There is increasing global concern with environmental food production and sustainability to maintain high carbon stocks in soil biomass. The biomass produced in crop-livestock integration system increases soil organic matter, acts in nutrient cycling, improves the physical, chemical and biological characteristics of soil and increases grain production. Moreover, this soil management system mitigates greenhouse effect and preserves the environment. However, in the Savannah of Central Brazil region, an efficient mulching production of biomass is one of the factors limit sustainability of direct seeding of soybean, mainly due to accelerated decomposition of crop residues. Thus, this study aimed to evaluate biomass dynamics of pearl millet and Paiaguas palisadegrass in different forage systems and sowing periods on soybean yield. The experiment followed a randomized block design with a 5 x 2 factorial arrangement and three replications, under five forage systems (monocropped pearl millet, monocropped Paiaguas palisadegrass, pearl millet intercropped in rows with Paiaguas palisadegrass, pearl millet intercropped between rows of Paiaguas palisadegrass and pearl millet oversown and intercropped with Paiaguas palisadegrass) at two sowing periods (February and March). The results showed that Paiaguas palisadegrass in a monocropped system generated the highest biomass production and lowest carbon/nitrogen ratio. The highest carbon/nitrogen ratio and cumulative biomass loss occurred with millet in monocropped and intercropped with oversown Paiaguas palisadegrass in which biomass production was reduced by plant competition. Paiaguas forage systems in palisadegrass monocropped and intercropping on and between rows supported higher yield of soybean. The second sowing periods resulted in higher production of remaining biomass and grain yield, in all forage systems. Intercropping in crop-livestock integration systems showed a promising cultivation technique to maintain a sustainable stock of soil carbon. Key words: Carbon/nitrogen ratio, half-lives, [Pennisetum glaucum (L.) R. Br.], Urochloa brizantha cv. BRS Paiaguas.

Evaluation of novel thermo-resistant Micractinium and Scenedesmus sp. for efficient biomass and lipid production under different temperature and nutrient regimes

Despite the vast interest in microalgae as feedstock for biodiesel production, relatively few studies examined their response to diurnal temperature fluctuation. Here, we describe biomass and lipid productivities and fatty acid profiles of thermo-resistant Micractinium sp. and Scenedesmus sp. grown in batch cultures in a laboratory set-up that mimics a typically warm summer day in Central Anatolia with a 16-h light temperature of 30°C and 8-h dark temperature of 16°C (30°C (day)/16°C (night)). Both strains can survive a temperature range of 10–50°C. We found the lipid productivities of Micractinium sp. and Scenedesmus sp. as 30/21mgL−1d−1 and 6/7mgL−1d−1, respectively during the 30°C (day)/16°C (night) cycle. Saturated fatty acid content increased with increasing temperature. Additionally, we cultured Micractinium sp. under Nitrogen (N) and Phosphorus (P) limiting conditions. Highest lipid productivity of 85.4±2mgL−1d−1 was obtained under P-depletion during exponential growth phase. Oleic acid amount also increased eight fold during P-deplete.

Whey as a renewable source for lipid production by Rhodococcus strains: Physiology and genomics of lactose and galactose utilization

We investigated biomass and lipid production from whey by different Rhodococcus strains. The studied microorganisms exhibited different capability for growing and producing lipids from whey permeate. Strains belonging to R. opacus exhibited high yields of biomass (6.1–6.3 g/L) and lipid content (45–48% of CDW), whereas R. jostii, R. erythropolis, R. fascians, and R. equi strains produced low biomass (1.8–2.9 g/L) and lipids (lesser than 5% of CDW) from whey. Lactose and galactose, which are main constituents of whey, supported growth of R. opacus strains, but not of the other investigated species. A genome‐wide bioinformatic analyses demonstrated that some genes coding for transport systems (LacEFGK) and the β‐galactosidase (LacB) enzyme for lactose cleavage are lacking in such species, which may explain their inability to utilize lactose, galactose, and whey for an efficient biomass and lipid production. R. opacus possesses a complete genetic endowment for degrading lactose, galactose, and whey as well as for lipid biosynthesis from such substrates. Thus, R. opacus is a robust candidate for single‐cell oil production from whey. The cultivation of R. opacus cells on crude whey resulted in an increase of lipid production from 3.0 to 6.4 g/L, in comparison to whey permeate.Practical application: This study demonstrates that the bioconversion of whey to oils by Rhodococcus strains is feasible. However, we found some genetic and physiological differences for whey, lactose and galactose catabolism and assimilation among rhodococcal species. Our results demonstrate that among five different rhodococcal species, Rhodococcus opacus has the more robust genetic endowment for supporting high yields of biomass and lipid production from whey. The use of whey for single cell oil production by rhodococci may serve as platform for developing environmentally friendly biotechnological processes.The use of whey for single cell oil production by rhodococci may serve as platform for developing environmentally friendly biotechnological processes.

Predicting Specific Biogas Yield of Maize-Validation of Different Model Approaches

A reliable tool for predicting the specific biogas yield (SBY) of maize is required for breeding purposes to support a more efficient biomass production and for a quality-based payment of maize-substrate supply. The objective of the current study was to validate the recently published prediction model by Rath et al. (Bioenergy Research 6:939–952) with an independent data set and to compare its predictive ability to the approaches of four previously reported models (Baserga, Keymer and Schilcher, Kaiser, Weisbach). The validation data set was based on a multisite field experiment, providing a large genotypic variation in maize chemical composition and SBY, which ranged between 612 and 826 lN kg−1 OM. Predicted and measured SBY were positively correlated (r = 0.15 to r = 0.48) for all approaches tested. The model by Rath et al. revealed the highest predictive ability and was the only approach that allowed the variability of SBY within the data set to be reflected. This could be attributed to an extensive and reliable calibration database covering the genotype × environment interaction, which allowed a thorough examination of the assumptions before conducting a multiple linear regression analysis. Even with this provision, sufficient samples per genotype are obviously required to predict satisfactorily the ranking of maize genotypes with respect to SBY. Using genotype averages over sites, instead of single-location values, is recommended to reduce the strong impact of weather conditions on the chemical composition, thereby enabling a more reliable estimate of the genotype SBY potential.

Biodiesel production using chemical and biological methods – A review of process, catalyst, acyl acceptor, source and process variables

The indiscriminate extraction and consumption of fossil fuels have left the world with a corner kick into the area of exponential fuel demand and now the race is on for alternate energy source. The fortunate improvements in Biodiesel fuel production techniques has been the heading topic of economic and environment sustainability so far. Biodiesel have the potential to replace diesel in vehicle engines. It has been tested and proved that engines running on biodiesel have shown low smoke emission and low toxic gas emission. Biodiesel properties such as oxidation stability, cloud point, iodine value, linoleic acid and poly-unsaturated fatty acid methyl ester content of biodiesel are dependent upon the quality of the feedstock. Processing parameters such as density, viscosity, acid value, distillation property are dependent on feedstock as well as the reaction conditions or the extent of reaction. Combustion property greatly varies with the substrates used and almost all the varieties have been proven to be as superior as that of conventional diesel fuel. Though the existing fossil and terrestrial biomass based oil cannot realistically satisfy the existing demands, algal oil source scores the most out of demanded factors like oil content, extractability, comfortable cultivation and efficient biomass production. Algae are a diverse group of plant like microorganisms, prokaryotic and eukaryotic, mostly autotrophic in nature with basic requirement such as CO 2 and light for their normal growth and metabolic activity. Being micro scaled in physiology, most species of algae have less doubling time and the oil productivity greatly exceeds the outcome of best oil producing crops which clearly portrays that microalgae acts as a renewable source and can yield enough amount of oil for biodiesel production to meet the present intensifying demands. This article aims at reviewing the technical aspects of various biodiesel production methods from diverse oil feedstocks, their importance and significance of microalgal, process availability, commercialization potential of various processes.

SUSTAINABLE NUTRIENT MANAGEMENT PACKAGE FOR COST-EFFECTIVE BIOENERGY BIOMASS PRODUCTION

Commercial fertilizer (particularly nitrogen) costs account for a substantial portion of the total production costs of cellulosic biomass and can be a major obstacle to biofuel production. In a series of greenhouse studies, we evaluated the feasibility of co-applying Gibberellins (GA) and reduced nitrogen (N) rates to produce a bioenergy crop less expensively. In a preliminary study, we determined the minimum combined application rates of GA and N required for efficient biomass (sweet sorghum, Sorghum bicolor) production. Co-application of 75 kg ha−1 (one-half of the recommended N rate for sorghum) and a modest GA rate of 3 g ha−1 optimized dry matter yield (DMY) and N and phosphorus (P) uptake efficiencies, resulting in a reduction of N and P leaching. Organic nutrient sources such as manures and biosolids can be substituted for commercial N fertilizers (and incidentally supply P) to further reduce the cost of nutrient supply for biomass production. Based on the results of the preliminary study, we conducted a second greenhouse study using sweet sorghum as a test bioenergy crop. We co-applied organic sources of N (manure and biosolids) at 75 and 150 kg PAN ha−1 (representing 50 and 100% N rate respectively) with 3 g GA ha−1. In each batch of experiment, the crop was grown for 8 wk on Immokalee fine sand of minimal native fertility. After harvest, sufficient water was applied to soil in each pot to yield ∼1.5 L (∼0.75 pore volume) of leachate, and analyzed for total N and soluble reactive P (SRP). The reduced (50%) N application rate, together with GA, optimized biomass production. Application of GA at 3 g ha−1, and the organic sources of N at 50% of the recommended N rate, decreased nutrient cost of producing the bioenergy biomass by ∼$375 ha−1 (>90% of total nutrient cost), and could reduce offsite N and P losses from vulnerable soils.

Net ecosystem production and carbon balance of an SRC poplar plantation during its first rotation

To evaluate the potential of woody bioenergy crops as an alternative energy source, there is need for a more comprehensive understanding of their carbon cycling and their allocation patterns throughout the lifespan. We therefore quantified the net ecosystem production (NEP) of a poplar (Populus) short rotation coppice (SRC) culture in Flanders during its second growing season.Eddy covariance (EC) techniques were applied to obtain the annual net ecosystem exchange (NEE) of the plantation. Further, by applying a component-flux-based approach NEP was calculated as the difference between the modelled gross photosynthesis and the respiratory fluxes from foliage, stem and soil obtained via upscaling from chamber measurements. A combination of biomass sampling, inventories and upscaling techniques was used to determine NEP via a pool-change-based approach.Across the three approaches, the net carbon balance ranged from 96 to 199 g m−2 y−1 indicating a significant net carbon uptake by the SRC culture. During the establishment year the SRC culture was a net source of carbon to the atmosphere, but already during the second growing season there was a significant net uptake. Both the component-flux-based and pool-change-based approaches resulted in higher values (47–108%) than the EC-estimation of NEE, though the results were comparable considering the considerable and variable uncertainty levels involved in the different approaches. The efficient biomass production – with the highest part of the total carbon uptake allocated to the aboveground wood – led the poplars to counterbalance the soil carbon losses resulting from land use change in a short period of time.

Potato Feedstock as an Organic Carbon Source for Efficient Biomass and Lipid Production by the Heterotrophic Microalga Chlorella protothecoides

Microalgae can grow heterotrophically with glucose as a carbon source to accumulate high amounts of lipids, which are one of the most promising feedstock for biodiesel production. However, glucose is one of the main contributors in the high cost of microalgae culture. This study was to evaluate the feasibility of using potato starch hydrolysate (PSH) instead of glucose as a carbon source for microalgal lipid production. When PSH was used as a carbon source for the heterotrophic microalga Chlorella protothecoides, the highest biomass and total lipid yields were 20.23 and 10.43 g/L, respectively, representing 1.3- and 1.4-fold higher than those obtained when glucose is used as a carbon source. A noticeable increase in the number of oil droplets was observed in the PSH-feeding algal cells. In addition, the calorific value was significantly increased to 29.08 kJ/g compared to the calorific value of 22.65 kJ/g from the cells grown in glucose medium. These findings confirmed that the lipid content greatly impro...

Solid Oxide Fuel Cell for Efficient Energy Production and Clean-Up of Wet Biomass

not Available.

Effects of cross host species inoculation of nitrogen‐fixing endophytes on growth and leaf physiology of maize

AbstractPlants that grow and thrive under abiotic stress often do so with the help of endophytic microorganisms. Although nitrogen‐fixing (diazotrophic) endophytes colonize many wild plants, these natural relationships may be disrupted in cultivated crop species where breeding and genotype selection often occur under conditions of intensive fertilization and irrigation. Many energy crops including corn may still benefit from diazotrophic endophyte inoculations allowing for more efficient biomass production with less input of petroleum‐derived fertilizer. A selection of diazotrophic endophytes isolated from willow (Salix sitchensis, Sitka willow) and poplar (Populus trichocarpa, black cottonwood) growing in nutrient‐poor river sides were used as inoculum in three experiments testing the effect on plant growth and leaf level physiology of a sweet corn variety under various levels of applied nitrogen fertilizer. We report substantial growth promotion with improved leaf physiology of corn plants in response to diazotrophic endophyte inoculations. Significant gains of early biomass with a greater root : shoot ratio were found for plants receiving endophytic inocula over the uninoculated control groups regardless of the nitrogen level. Furthermore, inoculated plants exhibited consistently higher rates of net CO2 assimilation than did those without endophytic inoculation. These results have beneficial implications for enhanced plant growth in a low‐input system on nutrient‐poor sites. The immediate increase of root mass observed in endophyte inoculated plants has the potential to provide better establishment and early growth in resource‐limited environments. The initial results of this study also indicate that the beneficial effect from endophytes isolated from poplar and willow species is not restricted to the species from which they were initially isolated.

A metabolic prosurvival role for PML in breast cancer

Cancer cells exhibit an aberrant metabolism that facilitates more efficient production of biomass and hence tumor growth and progression. However, the genetic cues modulating this metabolic switch remain largely undetermined. We identified a metabolic function for the promyelocytic leukemia (PML) gene, uncovering an unexpected role for this bona fide tumor suppressor in breast cancer cell survival. We found that PML acted as both a negative regulator of PPARγ coactivator 1A (PGC1A) acetylation and a potent activator of PPAR signaling and fatty acid oxidation. We further showed that PML promoted ATP production and inhibited anoikis. Importantly, PML expression allowed luminal filling in 3D basement membrane breast culture models, an effect that was reverted by the pharmacological inhibition of fatty acid oxidation. Additionally, immunohistochemical analysis of breast cancer biopsies revealed that PML was overexpressed in a subset of breast cancers and enriched in triple-negative cases. Indeed, PML expression in breast cancer correlated strikingly with reduced time to recurrence, a gene signature of poor prognosis, and activated PPAR signaling. These findings have important therapeutic implications, as PML and its key role in fatty acid oxidation metabolism are amenable to pharmacological suppression, a potential future mode of cancer prevention and treatment.

Biomass production and soil nutrient removal by switchgrass grown for biofuel production

With the energy crisis, interest is being focused on biofuel crops such as switchgrass. Efficient production of biomass from switchgrass to produce biofuel can contribute to helping address the energy problems faced by humankind. Research was implemented between 2008 and 2009 in Southeast Missouri, USA, to investigate the potential biomass production from switchgrass (Panicum virgatum cv. Alamo), and to monitor the changes in the uptake of N, P, K, Ca, Mg, Fe, Cu, Zn and Mn in the aboveground switchgrass biomass from May to November, in order to determine the optimum harvest time to produce the highest biomass yield with minimal nutrient removal. The maximum annual biomass production was 22–29.1 Mg ha-1. The date that the maximum biomass was obtained did not coincide with the minimum nutrient removal date. The nutrient uptake was dependant on the date of harvest, with the maximum being reached around July, followed by a significant decrease until the end of the season. During senescence, nutrients moved from the plant to the soil. Late November appeared to be the best date to harvest the switchgrass in order to minimize the nutrient removal and maximize biomass yield.

Effects of alginate oligosaccharide mixtures on the growth and fatty acid composition of the green alga Chlamydomonas reinhardtii

Alginate is a natural acidic linear polysaccharide that is produced by brown seaweeds. It is currently used in a broad range of commercial enterprises, such as the food and medical products industries. Recent evidence has demonstrated that alginate oligosaccharides may function as growth promoting agents for certain plant cells, including those of some green algae. Chlamydomonas reinhardtii is a green alga that is used as a model organism in fundamental molecular biology studies; it is also a producer of biohydrogen. In the present study, we examined effects of two types of alginate oligosaccharide mixtures (AOMs), which were prepared by either enzymatic degradation (ED) or acid hydrolysis (AH), on the growth of C. reinhardtii. Growth was significantly promoted by AOM (ED) in a concentration-dependent manner. The maximum effect was observed on day 4 of treatment. The fatty acid composition of C. reinhardtii was also influenced by AOM (ED); the levels of C16:0, C18:2 cis and C18:3 n-3 increased in treated cells. AOM (AH) and the other saccharides that we tested did not affect the growth of C. reinhardtii. The effects that we identified could promote efficient biomass production by reducing culture times and by changing cellular fatty acid levels.

Growth, photosynthesis and podophyllotoxin accumulation of Dysosma versipellis in response to a light gradient and conservation implications

Dysosma versipellis (Hance) M. Cheng ex Ying (Berberidaceae) is a rare and vulnerable, perennial herb endemic to China with pharmaceutical significance. Increasing habitat loss and over-exploitation of the plant has severely affected the plant’s in situ conservation, necessitating ex situ conservation and commercial cultivation. The light regime is a critical environmental factor contributing to successful ex situ conservation via efficient production of biomass and secondary metabolites. We investigated the responses of 2-year-old D. versipellis plants to a light gradient in terms of leaf morphology, growth, biomass production, photosynthesis and podophyllotoxin (PTOX) accumulation. D. versipellis responded to the light gradient in terms of plant height, leaf size, leaf photosynthesis and PTOX accumulation. Plants demonstrated optimal vegetative growth, photosynthetic capability, and PTOX production, under a light intensity equal to 30% full sunlight. Half full sunlight led to the lowest production of PTOX despite having no obviously different effects on growth. Full sunlight was able to cause leaf death in mid-summer (July), although these plantlets did not significantly differ in growth or biomass production before July and new leaves emerged in August. D. versipellis is therefore proposed to be a shade-tolerant plant, well adapted to variations in irradiance. Irradiance of 10%–50%, particularly ca. 30% full sunlight is strongly recommended for ex situ conservation and commercial cultivation.

STUDY ON BIOLOGICAL CHARACTERISTICS OF HETEROTROPHIC MARINE MICROALGA-SCHIZOCHYTRIUM MANGROVEI PQ6 ISOLATED FROM PHU QUOC ISLAND, KIEN GIANG PROVINCE, VIETNAM(1).

Schizochytrium sp. PQ6, a heterotrophic microalga isolated from Phu Quoc (PQ) Island in the Kien Giang province of Vietnam, contains a high amount of docosahexaenoic acid (DHA, C22:6n-3). In this study, the culture conditions are developed to maximize biomass and DHA production. Nucleotide sequence analysis of partial 18S rRNA gene from genomic DNA showed that PQ6 has a phylogenetic relationship close to Schizochytrium mangrovei Raghu-Kumar. The highest growth rate and DHA accumulation of this strain were obtained in 6.0% glucose, 1.0% yeast extract, 50% artificial seawater (ASW), and pH 7 at 28°C. In addition, carbon and nitrogen sources could be replaced by glycerol, ammonium acetate, sodium nitrate, or fertilizer N-P-K. Total lipid content reached 38.67% of dry cell weight (DCW), in which DHA and eicosapentaenoic acid (EPA, C20:5n-3) contents accounted for 43.58% and 0.75% of the total fatty acid (TFA), respectively. In 5 and 10 L fermenters, the cell density, DCW, total lipid content, and maximum DHA yield were 46.50 × 10(6) cells · mL(-1) , 23.7 g · L(-1) , 38.56% of DCW, and 8.71 g · L(-1) (in 5 L fermenter), respectively, and 49.71 × 10(6) cells · mL(-1) , 25.34 g · L(-1) , 46.23% of DCW, and 11.55 g · L(-1) (in 10 L fermenter), respectively. Biomass of PQ6 strain possessed high contents of Na, I, and Fe (167.185, 278.3, and 43.69 mg · kg(-1) DCW, respectively). These results serve as a foundation for the efficient production of PQ6 biomass that can be used as a food supplement for humans and aquaculture in the future.