Micractinium Pusillum Research Articles

Exploring microalgal nutrient-light synergy to enhance CO2 utilization and lipid productivity in sustainable long-term water recycling cultivation

In this work the effects of nutrient availability and light conditions on CO2 utilization and lipid production in Micractinium pusillum KMC8 is reported. The study investigated the ideal nitrogen concentrations for growth and nitrogen utilization in a 15% CO2 environment. Logistic and Gompertz models were employed to analyze the kinetics of KMC8 cell growth. Compared to 17.6 mmol L−1 control nitrogen, which generated 1.6 g L−1 growth, doubling and quadrupling nitrogen concentrations boosted biomass growth by 12.5% and 28.78%. At 8.6 mmol L−1 nitrogen, the growth decreased but lipid productivity increased to 18.62 mg L−1 day−1. At 70.6 mmol L−1 nitrogen, elevated nitrogen levels maintained an alkaline pH above 7 and enhanced CO2 mitigation, achieving 2.27% CO2 utilization efficiency. Nitrogen shows a positive correlation with higher rates of carbon and nitrogen fixation. The investigation extends to find out the influence of phosphorus and light conditions on microalgae. Increasing light intensity incrementally from 150 to 1200 μmol m−2 s−1 with more phosphorus increased biomass productivity by 85% (255 mg L-1 day−1) and lipid productivity by 2.5-fold (84.76 mg L-1 day−1), with 3.3% CO2 utilization efficiency compared to directly using 1200 μmol m−2 s−1. This study suggests a water recycling-fed batch cycle with gradual light feeding, which results in high CO2 fixation (1.1 g L−1 day−1), 7% CO2 utilization, and significant biomass and lipid productivity (577.23 and 150 mg L−1 day−1). This approach promotes lipid synthesis, maintains carbon fixation, and minimizes biomass loss, thus supporting sustainable bioenergy development in a circular bio-economy framework.

Taxonomic complexity analysis of the Chlorella clade (Chlorellaceae)

In this study, 253 of 18S rDNA sequences, 155 of ITS2 sequences, 63 of rbcL sequences, and 23 of tufA sequences were collected on GenBank to evaluate and analyse the taxonomic complexity of the Chlorella clade. C. vulgarisand C. sorokiniana had the most collected sequences of DNA barcoding. Analysis of phylogenetic tree results showed that the strains of these two species were divided into 2 to 3 small groups with genetic differences. In addition, different species belonging to the same clade in phylogenetic trees were observed. For example, Actinastrum hantzschii, C. chlorelloides, C. singularis, C. sorokiniana, C. thermophila, C. volutis, C. vulgaris, Micractinium pusillum, and M. reisseri belonged to the same group of the 18S rDNA phylogenetic tree. This showed the complexity in the taxonomy of the Chlorella clade came not only from the cryptic species, but also from the genetic relationships of the remaining species. Therefore, identifying and determining the relationship of Chlorella clade species have been still challenging, because of the complexity of the database on GenBank as well as the incomplete taxonomic system. Clarification of the genetic relationship is needed to improve the taxonomy and identification of new isolates of the Chlorella clade.

Acclimation-driven microalgal cultivation improved temperature and light stress tolerance, CO2 sequestration and metabolite regulation for bioenergy production

This study investigates temperature and light impact on the ability of Micractinium pusillum microalgae to mitigate CO2 and produce bioenergy in semi-continuous mode. Microalgae were exposed to temperatures (15, 25, and 35 °C) and light intensities (50, 350, and 650 μmol m−2 s-1), including two temperature cycles, 25 °C had the maximum growth rate, with no significant difference at 35 °C and light intensities of 350 and 650 μmol m−2 s−1. 15 °C temperature and 50 μmol m−2 s−1 light intensity reduced growth. Increased light intensity accelerated growth, CO2 utilization with carbon and bioenergy accumulation. Microalgae demonstrate rapid primary metabolic adjustment and acclimation reactions in response to changes in light and temperature conditions. Temperature correlated positively with carbon and nitrogen fixation, CO2 fixation, and carbon accumulation in the biomass, whereas there was no correlation found between light. In the temperature regime experiment, higher light intensity boosted nutrient and CO2 utilization, carbon buildup, and biomass bioenergy.

Influence of salinity and various nitrogen sources on cell growth and lipid production of the green microalga Micractinium pusillum Fresen.

Influence of salinity and various nitrogen sources on cell growth and lipid production of the green microalga Micractinium pusillum Fresen.

Maximize microalgal carbon dioxide utilization and lipid productivity by using toxic flue gas compounds as nutrient source

NOx and SOx present in flue gas inhibit microalgal based CO2 mitigation process. In this work, 13 microalgal strains were screened to evaluate their gradual acclimation capacity to toxic flue gas compounds, by testing their growth capability and photosynthetic ability in dissolved flue gas compounds. Six strains out of them were evaluated for their acclimation to bicarbonate and 15% CO2 as sole carbon sources. Two strains, Micractinium pusillum KMC8 and Scenedesmus acutus NCIM5584 were found to accumulate nitrite as fixed nitrogen and showed improved growth performance in photobioreactor upon stepwise acclimation to bisulphite/sulphite. Notably, the strain KMC8 showed a high tolerance and rapidly acclimated dissolved flue gas compounds with higher biomass yield (1.32 g L−1) and neutral lipid accumulation (32%), enhanced CO2 utilization efficiency (3.07%) and CO2 fixation rate (136.79 mg L−1 d−1) post acclimation. KMC8 sustained its stability in biomass and lipid productivity while simultaneously bio-mitigated CO2 under semi-continuous mode.

The Effect of Chromium on Photosynthesis and Lipid Accumulation in Two Chlorophyte Microalgae

Heavy metals have adverse effects on microalgae metabolism and growth. Photosynthesis and lipid profile are quite sensitive to heavy metal toxicity. The impact of hexavalent chromium—Cr(VI) on photosynthesis and lipid accumulation in Mucidosphaerium pulchellum and Micractinium pusillum exposed to different concentrations (0–500 μg L−1) was investigated for 11 days. A significant (p < 0.05) increase in lipid content was observed with increasing Cr(VI) concentration. However, growth was suppressed at higher concentrations exceeding 100 μg L−1. Addition of Cr(VI) in the cell culture medium showed a negative effect on quantum yield (Fv/Fm), and a photosynthetic inhibition of >65% was noted in both species at 500 μg L−1. However, the lipid gravimetric analysis presented inner cell lipid content up to 36% and 30% of dry weight biomass for M. pulchellum and M. pusillum, respectively. The fatty acids profiles of both microalgae species showed higher levels of hexadecenoic acid as well as ω3, ω6, and ω7 fatty acids. The effect of Cr(VI) on photosynthesis and lipid accumulation in both microalgae species was concentration and exposure time dependent. This shows that an appropriate concentration of Cr(VI) in culture medium could be beneficial for higher lipid accumulation in freshwater eukaryotic microalgae species.

Complete chloroplast of Micractinium pusillum CCAP 231/1 (chlorellaceae, trebouxiophyceae)

The chloroplast genome of Micractinium pusillum CCAP 231/1 was completely sequenced. This chloroplast genome has 115,638 bp in length and consists of 111 genes including 81 protein-coding, 4 rRNA, and 26 tRNA genes. The overall GC content of the genome is 35.3%.

Complete mitochondrial genome of Micractinium pusillum CCAP 231/1 (Chlorellaceae, Trebouxiophyceae)

The mitochondrial genome of Micractinium pusillum CCAP 231/1 was completely sequenced. This mitogenome has 70,061 bp in length and consists of 62 genes including 32 protein-coding, 3 rRNA, and 27 tRNA genes. The overall GC content of the genome is 31.3%.

Detoxification mechanism of organophosphorus pesticide via carboxylestrase pathway that triggers de novo TAG biosynthesis in oleaginous microalgae

Organophosphorus compounds exhibit a wide range of toxicity to mammals. In this study the effect of malathion on the growth and biochemical parameters of microalgae was evaluated. Three microalgae (Micractinium pusillum UUIND2, Chlorella singulari UUIND5 and Chlorella sorokiniana UUIND6) were used in this study. Among the three algal strains tested, Chlorella sorokiniana UUIND6 was able to tolerate 100 ppm of malathion. The photosynthetic pigments, the protein, carbohydrate and lipid contents of microalgal cells were also analyzed. About 90% degradation was recorded in 25 ppm, 50 ppm and 70% was recorded in 100 ppm of malathion by Chlorella sorokiniana. A mechanism of degradation of malathion by Chlorella sorokiniana is proposed in this study. Activity of carboxylesterase was increased in algal cells cultivated in malathion containing medium which confirmed that malathion degraded into phosphate. Increased amount of Malondialdehye (MDA) indicate the development of free radicals under the stress of malathion which substantialy increase de novo TAG biosynthesis, while increased level of superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) suggested their association in scavenging of free radical.

Pretreated animal and human waste as a substantial nutrient source for cultivation of microalgae for biodiesel production.

The use of human and animal wastes for fertilization of aquaculture ponds has been practiced for thousands of years. In the present work, we have used the excreta (human urine, poultry waste, cow dung, and urine) as a nutrient source for the cultivation of Chlorella singularis, Micractinium pusillum, and Chlorella sorokiniana strains of microalgae. Different solid wastes were treated with 60mM H2SO4 for the extraction of nutrients. After treatment, the supernatant of different solid wastes and liquid waste were diluted 5, 10, 15, and 20% to be used as a media for the cultivation of microalgae. Chlorella sorokiniana was able to grow in all concentration of excreta media. The maximum growth rate 140 ± 3.1mg/L/day and lipid production (45.5 ± 2.3mg/L/day) was obtained in 20% poultry. Among the different excreta media used for cultivation of microalgae, poultry media displayed the best results and thus, should be used for large scale cultivation of microalgae.

Mass development of phytoplankton in the River Warta in Poznań (Poland) in the 21st century

Abstract The first studies of phytoplankton of the River Warta in Poznań (Poland) were carried out in the 20th century (in 1922–23 and 1950–57). In the growing seasons the dominant groups were diatoms and green algae. Cyanobacteria were noted, but they did not have high abundance. The aim of this work is to present the phytoplankton research conducted on the River Warta in Poznań in the 21st century (in 2003, 2009, 2010 and 2016). In all years the dominance of diatoms and green algae in terms of biomass was noted. However, in late summer cyanobacteria biomass was high and this group became dominant or co-dominant. Spring blooms were created by unicellular centric diatoms, e.g. Stephanodiscus minutulus and colonial green algae: Coelastrum microporum or Micractinium pusillum. In summer, bloom-forming taxa were unicellular centric diatoms, colonial diatoms: Aulacoseira granulata or Fragilaria crotonensis and cyanobacteria: Aphanizomenon flos-aquae and Woronichinia naegeliana. The occurrence of taxa typical of dam reservoirs and lakes suggests the influence of the Jeziorsko Reservoir on the phytoplankton of the River Warta, but it does not exclude the impact of tributaries and oxbow lakes. The research conducted in the 20th and 21st century show important changes in the taxonomical structure and abundance of phytoplankton.

Potential of five different isolated colonial algal species for wastewater treatment and biomass energy production

Wastewater treatment high rate algal pond (WWT HRAP) performance and the potential for low-cost biofuel production from its biomass are affected by the composition of the algal community. While several unicellular algal species have been evaluated extensively for their wastewater treatment and biofuel production potential, there has been little focus on the colonial species that typically predominate in high rate algal ponds and which have the benefit of being easily harvested by cost-effective, simple gravity settling. This study investigates the wastewater treatment performance of five wastewater colonial algal species that are common in high rate algal ponds: Mucidosphaerium pulchellum, Micractinium pusillum, Coleastrum sp., Desmodesmus sp. and Pediastrum boryanum and their potential value for biofuel production in terms of their biochemical composition and biomass energy yield. The algae were isolated from pilot-scale WWT HRAPs and used in batch monoculture experiments with pre-frozen and pre-filtered primary settled sewage that were conducted over 10days under simulated New Zealand summer and winter conditions. Under summer conditions, all species showed similar efficient nutrient removal (>95% of NH4+-N and >85% of PO43−-P within 4days) whereas, under winter conditions, only the Mucidosphaerium pulchellum and Micractinium pusillum cultures showed efficient nutrient removal by the end of the experiment. Algal biomass yield, lipid and energy content varied with species and were higher in summer than winter (respectively 991–1700mg/L, 14.4–48.2wt% and 19.1–25kJ/g in summer, and 158.7–584mg/l, 15.1–31.4wt% and 17.7–21.1kJ/g in winter). The Mucidosphaerium pulchellum and Micractinium pusillum cultures had the highest biomass yield, lipid and energy content under both summer and winter conditions. However the settleability of Micractinium pusillum is much better than Mucidosphaerium pulchellum suggesting that of the colonial algal species tested, Micractinium pusillum has the greatest potential for both wastewater treatment and low-cost energy production in WWT HRAP.

Influence of CO2 and light spectra on the enhancement of microalgal growth and lipid content

The effect of different light spectrum and CO2 concentrations on the growth and lipid content of Micractinium pusillum and Ourococcus multisporus was investigated. The highest biomass yields (2.9 and 2.6 g-dry cell weight l−1) were observed for M. pusillum and O. multisporus, respectively, at 5% CO2 with red light illumination. Red light spectrum with 5% CO2 supported the highest lipid contents (20% and 27%) and lipid productivity (32 and 36 mg l−1 d−1) for M. pusillum and O. multisporus, respectively. The highest fatty acid methyl esters content for both microalgal species was observed under red light spectrum and 5% CO2 conditions, with the oleic acid fraction ranging between 35% and 37%. This study showed that the red light spectrum and 5% CO2 were the optimum conditions for maximum growth, lipid content and lipid productivity of both microalgae species, which could be further exploited to establish a microalga-based biodiesel production strategy.

English

Biodiesel production from microalgae depends on the algal biomass and lipid content. Both biomass production and lipid accumulation are limited by several factors in which nutrients play a key role. We investigated the influences of micronutrients on biomass, and lipid content of Micractinium pusillum GU732425 cultivated in bold basal media (BBM). The average dry biomass of microalgal strain in control medium reached 0.34 ± 0.01 g /L, while doubling (2X) the levels of Mn and Cu concentration increased the dry biomass to 0.38 ± 0.01 and 0.37 ± 0.02 g /L, respectively. M. pusillum cultivated in control medium had a biomass of 0.82 ± 0.05 g/L and a lipid productivity of 0.33 ± 0.02 g/L after 17 day cultivation. The alga cultivated in BBM with 4X Mn or 4X Cu produced more biomass (1.25 ± 0.01 or 1.28 ± 0.04 g dw/L) and lipid productivity (0.45±0.04 or 0.47±0.05 g/L), respectively. M. pusillum cultivated in different growth media had fatty acid compositions mainly comprising linoleic (49-54%), palmitic (24-29%), linolenic (16-22%), and oleic acids (2-5%). These results can be used to maximize the production of microalgal biomass and lipids in optimally designed photobioreactors. Key words: Micractinium pusillum, biomass, lipid production, media composition, fatty acids, trace metals

Novel molecular insights into nitrogen starvation-induced triacylglycerols accumulation revealed by differential gene expression analysis in green algae Micractinium pusillum

Microalgae usually accumulate triacylglycerols (TAGs) under stress conditions, especially during nitrogen (N) starvation. However, little information is available regarding the underlying mechanism. In the present study, a green algae Micractinium pusillum accumulated significant amounts of TAGs after 6 d of N starvation. Aiming at fundamental elucidation of the molecular mechanisms involved in N starvation-induced TAG accumulation, the global gene expression changes were identified by using suppression subtractive hybridization (SSH). In total, 290 expressed sequence tags (ESTs) showed significant differential expression between the treated and control samples. The expression profiles of 19 ESTs have been confirmed by quantitative real-time PCR (qPCR). Homology analysis showed that the 174 N deficiency-induced ESTs were mainly involved in carbohydrate metabolism, pyruvate and acetyl-CoA synthesis, isoprenoids biosynthesis, and TAG degradation, as well as a severe down-regulation in the expression of 116 genes related to photosynthesis, cell growth, amino acid synthesis and cell cycle regulation. A significant decrease in carbohydrate content was also observed in the N-deficient algal cells. These results suggested that the carbon sources for TAG biosynthesis were largely derived from carbohydrate metabolism rather than from photosynthesis. The results of the qPCR showed that, compared to the control, the transcript levels of genes related to pyruvate and acetyl-CoA synthesis were dramatically increased over 100 times after N starvation, which suggests that pyruvate and acetyl-CoA play important roles in driving carbon flow into TAG biosynthesis.

Photosynthetic efficiency and lipid accumulation are affected by the concentration of carbon in microalgae Micractinium pusillum Y-002

A micro-algae strain was isolated from fresh tropical water in Hainan, China. By phylogenetic analysis with 18S rDNA, we identified it as Micractinium pusillumstrain Y-002. To study the relationships between nutrient and lipid accumulation of this strain, we cultured the organism either in complete TAP, SE, BG11 or HSM medium, or media deficient of nitrogen and iron, respectively. HSM media deficient in sulfur, phosphorus (P), magnesium (Mg), potassium (K) or calcium (Ca) were also tested. We found that HSM media, N and S starvation led to significant increase in cellular lipid content; and starvation of Ca and K only resulted in moderate increase of lipid content. Under the HSM-N or HSM-S culture condition, the increase in lipid content was accompanied by marked decrease in photosynthesis efficiency, total protein, and total carbohydrate content. Our investigation of the effect of exogenous carbon on lipid accumulation and photosynthetic efficiency revealed that the cell growth rate, photosynthesis efficiency, and lipid content per volume unit peaked in the presence of 15 mM sodium acetate (NaAC) and higher concentrations of NaAC led to decrease in these physiological traits. Key words: Micractinium pusillum, lipid content, photosynthetic efficiency, growth rate, biodiesel.

Characterization of microalgal species isolated from fresh water bodies as a potential source for biodiesel production

Due to increasing oil prices and climate change concerns, biodiesel has gained attention as an alternative energy source. Biodiesel derived from microalgae is a potentially renewable and carbon–neutral alternative to petroleum fuels. One of the most important decisions in obtaining oil from microalgae is the choice of algal species to use. Eight microalgae from a total of 33 isolated cultures were selected based on their morphology and ease of cultivation. Five cultures were isolated from river and identified as strains of Scenedesmus obliquus YSR01, Nitzschia cf. pusilla YSR02, Chlorella ellipsoidea YSR03, S. obliquus YSR04, and S. obliquus YSR05 , and three were isolated from wastewater and identified as S. obliquus YSW06 , Micractinium pusillum YSW07, and Ourococcus multisporus YSW08, based on LSU rDNA (D1-D2) and ITS sequence analyses. S. obliquus YSR01 reached a growth rate of 1.68 ± 0.28 day −1 at 680 nm and a biomass concentration of 1.57 ± 0.67 g dwt L −1, with a high lipid content of 58 ± 1.5%. Under similar environmental conditions, M. pusillum reached a growth rate of 2.3 ± 0.55 day −1 and a biomass concentration of 2.28 ± 0.16 g dwt L −1, with a relatively low lipid content of 24 ± 0.5% w/w. The fatty acid compositions of the studied species were mainly myristic, palmitic, palmitoleic, oleic, linoleic, g-linolenic, and linolenic acids. Our results suggest that S. obliquus YSR01 can be a possible candidate species for producing oils for biodiesel, based on its high lipid and oleic acid contents.

Polyphyletic distribution of bristle formation in Chlorellaceae: Micractinium, Diacanthos, Didymogenes and Hegewaldia gen. nov. (Trebouxiophyceae, Chlorophyta)

SUMMARYIn the traditional sense, several families of Chlorococcales sensu lato, such as Golenkiniaceae, Micractiniaceae, and Scenedesmaceae contained taxa with bristle formation, whereas the Chlorellaceae contained only genera without bristles. However, phylogenetic analyses of the small subunit (SSU) and internal transcribed spacer (ITS) rDNA sequences have shown that the genera Micractinium, Diacanthos (formerly Micractiniaceae) and Didymogenes (formerly Scenedesmaceae) are closely related to the genus Chlorella. The bristle formation within the Chlorella‐clade is originated independently in four lineages: Micractinium pusillum, Diacanthos belenophorus, Didymogenes anomala, and Micractinium parvulum (also known as Golenkinia minutissima). The latter species is to exclude from the genus Micractinium. Consequently, we proposed the new genus Hegewaldia and transferred M. parvulum to this genus. In contrast, Diacanthos belenophorus is closely related to Micractinium pusillum. As a result, the new combination (Micractinium belenophorum comb. nov.) is proposed. Comparisons of the secondary structure of ITS‐1 and ITS‐2 rDNA sequences among the strains of Didymogenes and Hegewaldia are provided to support the species concept in these genera.

농업용수 수질관리를 위한 미세조류의 활용

The objective of this research was to review the correlation between microalgae and agricultural water quality. Although microalgae has been considered as an essential factor for control1ing of water ecosystem, little attention has been paid for evaluating of microalgae as an important factor for water quality management. But it can be use to make us know the water pollution state at saprobic system, LTSI (Lake Tropic State Index), DAIpo (Diatom Assemblage Index to Organic Pollution), and AGP (Algal growth potential). In saprobic system, it is used microalgae such as Actinastrum hantzschii var. fluviatile, Asterionella gracillima, Coelastrum microporum, Synedra acus, Dictyosphaerium pulchellum, Micractinium pusillum, Cyclotella meneghiniana, Microcystis aeruginosa, Scenedesmus quadricauda, and Nitzschia palea for assessment water quality. In addition, they have ecologically significant characteristics such as dominant species, cosmopolitan species, redtide causative species etc. Also, microalgae such as Botryococcus braunii, B. sp., Chlorella vulgaris, C. sp., Phormidium sp., Scenedesmus quadricauda, Selenastrum capricornutum, Spirulina maxima, and S. platensis have an effect on improvement of water quality.

Effect and Bioaccumulation of Heavy Metals (Zn, Cd) on Micractinium pusillum Alga

Heavy metals (Zn and Cd) effect and their bioaccumulation by a microalga Micractinium pusillum were investigated. Results showed that Cd was more toxic than Zn on Micractinium pusillum. Indeed, inhibitory concentrations of 50% of alga population in 72h (IC50,72h) were 0.28 and 0.34 mg l−1 respectively for Cd and Zn. On the other hand, metal extracted rates from medium solution were more important for Zn than for Cd, essentially for the two first concentrations tested (0.06 and 0.12 mg l−1). Furthermore, Zn and Cd extracted proportions were more important for the low concentrations tested and decreased progressively with increasing concentrations applied. This mechanism of extraction corresponds principally to their biosorption by Micractinium pusillum.