Effects of directional adaptation on selenium tolerance and accumulation of heterotrophic Chlorella pyrenoidosa / 生物工程学报

Selenium (Se) is an essential trace element for organisms. Se deficiency will cause diseases such as Keshan disease and Kashin-Beck in human being, and huge loss to animal husbandry. Currently available Se supplements have such problems as low Se content, poor bioavailability, and poor safety. Chlorella pyrenoidosa can produce bioavailable and safe organic Se under suitable conditions, which is thus a promising Se supplement. Therefore, in this study, we tried to improve the Se tolerance and accumulation of C. pyrenoidosa by directional adaptation. To be specific, we gradually increased the concentration of Na2SeO3 in medium to domesticate C. pyrenoidosa and optimized the adapting time and concentration gradient of Na2SeO3 during the adaptation. The results showed that the adapted C. pyrenoidosa was more tolerant to Se and had stronger Se enrichment ability. In 5 L fermenter, the adapted strains could tolerate 40 mg/L Na2SeO3 and the synthesis rate of organic Se was 175.6% higher. Then, Se addition method in the 5 L fermenter was optimized. The result demonstrated that addition of Na2SeO3 at 40 mg/L during heterotrophic culture achieved the final dry weight of C. pyrenoidosa cells at 106.4 g/L, content of organic Se at 1 227 mg/kg, and synthesis rate of organic Se at 1.36 mg/(L·h). Compared with the reported highest cell density of 75 g/L and the highest organic Se content of 560 mg/kg, the corresponding figures in this study were 41.9% and 119.1% higher, respectively. In conclusion, directional adaptation can remarkably improve the Se tolerance and enrichment of C. pyrenoidosa.

High efficient assimilation of NO₃⁻-N with coproduction of microalgal proteins by Chlorella pyrenoidosa / 生物工程学报

The aim of this study was to establish a novel technology using microalgae for NO₃⁻ removal from high concentration wastewater and conversion to algal proteins. The effects of cultivation modes and illumination modes on the biomass yield, NO₃⁻ assimilation rate and algal protein yield were first investigated in shaking flasks for mixotrophic cultivation of Chlorella pyrenoidosa, and subsequently the scale-up verification in 5-L photo fermenter was successfully conducted. Fed-batch cultivation without medium recycling was the best cultivation mode in shaking flask system, in which the highest biomass yield (35.95 g/L), the average NO₃⁻ assimilation rate (2.06 g/(L·d)) and algal protein content (up to 42.44% of dry weight) were achieved. By using a staged increase of light intensity as illumination modes, the specific growth rate of cells could be significantly promoted to the highest (0.65 d⁻¹). After a 128-hour continuous cultivation in a 5-L photo fermenter, the highest biomass yield and the average NO₃⁻ assimilation rate were reached to 66.22 g/L and 4.38 g/(L·d) respectively, with the highest algal protein content at 47.13% of dry weight. Our study could provide a photo fermentation technology of microalgae for highly efficient treatment of waste industrial nitric acid and/or high concentration nitrate wastewater. This microalgae-based bioconversion process could coproduce protein-rich microalgal biomass, which facilitates the resource utilization of these type wastewater by trash-to-treasure conversion.

Effect of Chlorella pyrenoidosa on Influenza Virus Infected Mice / 日本補完代替医療学会誌

We orally administered Chlorella pyrenoidosa to mice 1 week before infection with the influenza virus up to 14 days after infection, and investigated its effects on mice with the viral infection. The survival rate was determined using the Kaplan-Meier cumulative survival curve, and the distilled water- and Chlorella-administered groups were assessed using the log-rank test. The duration of survival of the Chlorella-administered group was significantly extended (P=0.0394), and Chlorella showed high efficacy against influenza infection.

Bioassay-guided isolation of functional components from hot water extract of Chlorella pyrenoidosa / 生物工程学报

The main functional ingredients of hot water extract of Chlorella pyrenoidosa (CPE) were investigated through a bioassay-guided fractionation based on free radical scavenging and macrophage proliferation effects. The main functional ingredients of CPE were polysaccharides (PS) that were isolated by high pressure extraction, Sevag method, ethanol precipitation and ultrafiltration separation. Crude polysaccharides were further separated and purified by ion exchange chromatography DEAE52 and size exclusion chromatography Sephadex G-100. The purified fractions were analyzed by gel permeation chromatography. Molecular weights of the purified fractions PS-1-4-2, PS-1-3-2 and PS-2-3-3 were 3.97×10⁴, 2.28×10⁴ and 4.1×10³ Da, respectively. Bioassay-guided fractionation results indicated that CPE could remove free radicals and promote Ana-1 cells proliferation, mainly due to its various components working together. The components of free radicals scavenging mainly concentrated in PS-1-3, PS-1-4, PS-2-3 and PS-2-4. The components of Ana-1 proliferation mainly concentrated in PS-1-3, PS-1-4 and PS-2-3. This study established the activity screening method of main functional component from CPE, and got three new functional ingredients. It can be used to guide the development of high value products, further promote the industrialization process of microalgae energy, and realize microalgae 'high value products, microalgae energy and microalgae carbon' integration of exemplary role.

Effects of Allelochemicals from Ficus microcarpa on Chlorella pyrenoidosa

This study was performed in order to isolate and identify unknown allelochemicals from Ficus microcarpa, and to investigate the inhibitory to bloom-forming of green alga Chlorella pyrenoidosa. Through gradient elution, fraction C2, whose inhibition of alga growth in diverse extracts was the strongest was shown to cause significant reductions of maximum quantum yield, as well as electron transport rates of C. pyrenoidosa. The study data also showed that the increase of fraction C2 concentration decreased the activity of total superoxide dismutase (SOD), but increased the activities of catalase (CAT) and malondialdehyde (MDA) content. These results demonstrate that the active fraction C2 not only induced the photoinhibition or photodamage of PSII reaction centers, but also triggered the synthesis of reactive oxygen species which may change cell membrane penetrability, thereby leading to the eventual death of C. pyrenoidosa. Furthermore, the gas chromatography/mass spectrometry (GC/MS) analyses showed that the most potential allelochemical in active fraction C2 was 2-Propyl phenol, which may exhibit potent allelopathy.

The Toxic Effects of the Extracellular Active Components from One Algae-lysing Bacteria on Chlorella Pyrenoidosa / 微生物学通报

Toxic effects of L7 lyophilized powder of extracellular active components (L7-LPEAC), extracted from the Algae-lysing bacteria L7, on Chlorella pyrenoidosa were studied according to the changes of effective photosynthesis rate (EPR), the protein content, the chlorophyll a content and the MDA content of algae. The results showed that the growth of alga was promoted at low concentrations of L7-LPEAC (0.80 g/L, 1.25 g/L). The 96 h-EC50 and 120 h-EC50 upon Chlorella pyrenoidosa are 5.75 g/L and 2.55 g/L, respec tively. The chlorophyll a content increased firstly and then decreased at high concentrations of L7-LPEAC (≥2 g/L), so did the protein content. Compared with the control group, there is a significant statistics diff erence (P

Study on Microbial Oil Production with Chlorella pyrenoidosa / 微生物学通报

Chlorella pyrenoidosa No.2 was screened from five species of microalga Chlorella sp. for its higher lipid yield. Effects of medium components and culture conditions on cell growth as well as lipid ac-cumulation of C. pyrenoidosa No.2 were investigated and the results showed that the optimum medium rec-ipe was 20.0 g/L glucose,0.08 g/L glycine,1.0 g/L K2HPO4?3H2O,0.4 g/L MgSO4?7H2O and 0.004 g/L FeSO4?7H2O. The optimum culture temperature,initial pH,shaking rate and light intensity were 28℃,6.0,130 r/min and 650 Lux,respectively. Biomass and lipid content increased from 3.73 g/L and 40.15% to 6.56 g/L and 59.90% when Chlorella pyrenoidosa No.2 was cultivated under the above optimal conditions for 7 days,with lipid yield raised by 162%. Chlorella pyrenoidosa No.2 could produce lipid with xylose as carbon source,and so is potential for lipid production from renewable materials such as lignocellulose. GC analysis demonstrated that the fatty acid composition of the lipid was similar to that of vegetable oil and its unsaturated fatty acid content reached around 71%,thus it is a promising material for biodiesel production.

The Character of U(VI) Biosorption by Chlorella pyrenoidosa / 微生物学通报

The process of U(VI) biosorption by freshwater algae Chlorella pyrenoidosa and its absorption mechanism, absorption thermodynamics and absorption kinetics were investigated in this paper. The effects of pH, contact time, initial U(VI) concentration and temperature on biosorption were studied respectively. Research result showed that the absorption effect of U(VI) by Chlorella pyrenoidosa was affected by pH value of solution to a great extent, the absorption reached its balance within 5 min with optimal pH value 6 and max absorption quantity 2.7 mg/g. On the other hand, the absorption quantity of U(VI) by Chlorella pyrenoidosa was positively correlated with the initial concentration of U(VI); and the absorption quantity did not fluctuate remarkably when temperature was varied at the range of 20℃ to 30℃. Research result also showed that the process of U(VI) absorption was congruent with the second order kinetic model, and the correlation coefficient was high reaching to 0.99. It was suggested that the U(VI) biosorption by Chlorella pyrenoidosa was a complicated process consisting of many simultaneous reactions and could be described by Languir model quite well.