Exploration of applying growth-promotion bacteria of Chlorella sorokiniana to open cultivation systems.

Nowadays, artificial construction of bacteria-algae consortia to enhance microalgal biomass is prevalent in enclosed systems, while few are built in an open culture. In this study, Achromobacter sp. and Rhizobium sp., isolated from an open pond of Chlorella sorokiniana, were the microalgal growth-promotion bacteria and selected to build the bacteria-algae consortia with axenic C. sorokiniana in open cultivation systems. To examine the performance of these two artificial bacteria-algae consortia in open culture under stable cultivation conditions, the co-cultivation experiments were conducted under constant temperature and light intensity indoors. It was found that Achromobacter sp. gradually lost the dominance of the population in the co-culture and failed to promote the growth of C. sorokiniana during open cultivation. However, the Rhizobium sp. maintained its dominant population of bacterial community in open culture and could promote the growth of C. sorokiniana, with an enhancement of 13.76%. To further evaluate the effects of Rhizobium sp. on microalgae under variations of temperature and sunlight intensity conditions, the open co-cultivation experiments were built outdoors. Results showed that the growth of C. sorokiniana could rise 13.29% only when Rhizobium sp. was added to the culture continuously, and addition of bacterial solution in log-phase of microalgae could help Rhizobium sp. dominate in the bacterial community. In this way, addition of Rhizobium sp. in the log-phase of C. sorokiniana should be an effective process to be applied to open ponds cultivation. Our findings are a step toward applying growth-promotion bacteria for C. sorokiniana for applications in open cultivation systems.

Effect of culture condition on the growth, biochemical composition and EPA production of alkaliphilic Nitzschia plea isolated in the Southeast of China.

To overcome the contamination in open pond, microalgal strain selection should focus on species with tolerability to extreme environments. In this study, a native alkaliphilic algae, diatom Nitzschia plea was obtained in Southeast of China, which could tolerate high concentration of NaHCO3 (0.15 mol/L) and high pH (> 10). The effects of initial pH, light intensity and temperature on cell growth, biochemical composition and fatty acid profile of N. plea were investigated. Results indicated its specific growth rate could reach 1.2 day-1, lipid content was in the range 14.6-30.2% of dry weight, eicosapntemacnioc acid (EPA, C20:5) accounted for around 15% of total fatty acids. Alkalic condition benefited for both cell growth and EPA synthesis. Appropriately increasing light intensity and temperature could improve cell growth rate and lipid synthesis, although the proportion of EPA in total fatty acids decreased slightly. The optimal culture condition (pH 9.00, temperature 35.0 °C, light intensity 158.6 µmol/m2s) was suggested for maximum yield of EPA based on the response surface model. The overall biomass productivity and EPA productivity were 0.301 g/L/day and 7.43 mg/L/day, respectively. In conclusion, alkalic environment was helpful for the steady operation of open pond cultivation of N. plea with the characteristics of fast growth rate and high EPA content, which exhibited its commercial value.

Improved antifouling properties of photobioreactors by surface grafted sulfobetaine polymers.

To improve the antifouling (AF) properties of photobioreactors (PBR) for microalgal cultivation, using trihydroxymethyl aminomethane (tris) as the linking agent, a series of polyethylene (PE) films grafted with sulfobetaine (PE-SBMA) with grafting density ranging from 23.11 to 112 µg cm-2 were prepared through surface-initiated atom transfer radical polymerization (SI-ATRP). It was found that the contact angle of PE-SBMA films decreased with the increase in the grafting density. When the grafting density was 101.33 µg cm-2, it reached 67.27°. Compared with the PE film, the adsorption of protein on the PE-SBMA film decreased by 79.84% and the total weight of solid and absorbed microalgae decreased by 54.58 and 81.69%, respectively. Moreover, the transmittance of PE-SBMA film recovered to 86.03% of the initial value after cleaning, while that of the PE film recovered to only 47.27%. The results demonstrate that the AF properties of PE films were greatly improved on polySBMA-grafted surfaces.

[Clinical values and optimal cut-off points of basic vital signs in early identification of critical hand, foot, and mouth disease].

OBJECTIVE: To study the clinical values of basic vital signs in early identification of critical hand-foot-mouth disease (HFMD). METHODS: The clinical data of 358 children with severe HFMD [212 cases in stage 2 (central nervous system involvement) and 146 cases in stage 3 (earlier stage of cardiopulmonary failure, critical type)] were reviewed. The diagnostic values of peak temperature and duration of fever, as well as the heart rate (HR), respiratory rate (RR), systolic blood pressure (SBP), and diastolic blood pressure (DBP) in different age groups, for critical HFMD (stage 3) were analyzed using the receiver operating characteristic (ROC) curve. RESULTS: HFMD might progress to critical type in case of HR≥148.5 beats/minutes, RR≥36.5 times/minutes, SBP≥95 mm Hg, and DBP≥59 mm Hg among children aged 0-1 year. HR≥142.5 times/minutes, RR≥31.5 times/mintes, SBP≥103 mm Hg, and DBP≥60.5 mm Hg in children aged 1-2 years had a certain diagnostic value for critical HFMD. HFMD might progress to critical type in case of HR≥139.5 times/minutes, RR≥29.5 times/minutes, and SBP≥103 mm Hg among children≥3 years of age. The sensitivity and specificity of every indicator were higher than 0.517 and 0.769, respectively. The area under the ROC curve (AUC) for peak temperature was 0.507 (P=0.816, compared with AUC=0.5). When the duration of fever was ≥5.5 days, the sensitivity and specificity were 0.589 and 0.571, respectively. CONCLUSIONS: HR, RR, and BP are good indicators to identify critical HFMD (stage 3) early. The optimal cut-off points conform to the age characteristics of children. DBP in children≥3 years of age, peak temperature, and duration of fever have a low value in early identification of critical HFMD.

Outdoor cultivation of Chlorella sp. in an improved thin-film flat-plate photobioreactor in desertification areas.

In order to reduce the flow resistance of the thin-film flat plat photobioreactor (FPPBR) and make it more suitable for mass microalgae cultivation, the channel diameter was modified to 0.06 m and the thin-film FPPBR consisted of 10 parallel shunt-wound channels. A thin-film FPPBR system with 100 modified FPPBRs was constructed and used for Chlorella sp. cultivation in desertification areas (Ordos, China) from July to September of 2018. The pressure drop of the modified FPPBR system decreased significantly and the microalgae showed much higher productivity. The pressure drop was about 11.8 kPa when the liquid velocity was 0.238 m s-1. The final biomass concentration and area productivity reached 2.01 g L-1 and 49.79 g m-2 day-1 respectively, and the yearly productivity of Chlorella sp. was estimated to be about 15.24 t ha-2 year-1. The results demonstrated that high productivity of Chlorella sp. could be achieved in the improved FPPBR system in desertification areas and the improved FPPBR system was feasible for mass cultivation of microalgae in the commercial application.

Installation of flow deflectors and wing baffles to reduce dead zone and enhance flashing light effect in an open raceway pond.

To reduce the dead zone and enhance the flashing light effect, a novel open raceway pond with flow deflectors and wing baffles was developed. The hydrodynamics and light characteristics in the novel open raceway pond were investigated using computational fluid dynamics. Results showed that, compared with the control pond, pressure loss in the flow channel of the pond with optimized flow deflectors decreased by 14.58%, average fluid velocity increased by 26.89% and dead zone decreased by 60.42%. With wing baffles built into the raceway pond, significant swirling flow was produced. Moreover, the period of average L/D cycle was shortened. In outdoor cultivation of freshwater Chlorella sp., the biomass concentration of Chlorella sp. cultivated in the raceway pond with wing baffles was 30.11% higher than that of the control pond.

An optical-density-based feedback feeding method for ammonium concentration control in Spirulina platensis cultivation.

Cultivation of Spirulina platensis using ammonium salts or wastewater containing ammonium as alternative nitrogen sources is considered as a commercial way to reduce the production cost. In this research, by analyzing the relationship between biomass production and ammonium- N consumption in the fed-batch culture of Spirulina platensis using ammonium bicarbonate as a nitrogen nutrient source, an online adaptive control strategy based on optical density (OD) measurements for controlling ammonium feeding was presented. The ammonium concentration was successfully controlled between the cell growth inhibitory and limiting concentrations using this OD-based feedback feeding method. As a result, the maximum biomass concentration (2.98 g/l), productivity (0.237 g/l·d), nitrogen-to-cell conversion factor (7.32 gX/gN), and contents of protein (64.1%) and chlorophyll (13.4 mg/g) obtained by using the OD-based feedback feeding method were higher than those using the constant and variable feeding methods. The OD-based feedback feeding method could be recognized as an applicable way to control ammonium feeding and a benefit for Spirulina platensis cultivations.