Qingjie Hou

Effect of diethyl aminoethyl hexanoate on the accumulation of high-value biocompounds produced by two novel isolated microalgae

The low productivity of microalgae has restricted scale-up application of microalgae-based biodiesel processes. Diethyl aminoethyl hexanoate (DA-6) was investigated to enhance the biomass and metabolite productivity. At a very low concentration (10(-7)M) DA-6 made Chlorella ellipsoidea SDEC-11 and Scenedesmus quadricauda SDEC-13 obtain enlarged cell size, 114mgL(-1)d(-1), 101mgL(-1)d(-1) biomass productivity and 39.13mgL(-1)d(-1), 32.69mgL(-1)d(-1) lipid productivity, respectively. Biomass and lipid productivity of SDEC-11 and SDEC-13 were 100mgL(-1)d(-1) and 30.05mgL(-1)d(-1), 94mgL(-1)d(-1) and 28.43mgL(-1)d(-1), respectively, without DA-6. Twice hormone dose in 10(-6)M DA-6 medium resulted in higher biomass productivity (106mgL(-1)d(-1)) and longer exponential growth of SDEC-13. DA-6 also ensured the property of microalgae biodiesel to meet the EN 14214 standard. The current investigation demonstrated that DA-6 accelerated the microalgae growth and simultaneously improved the quality and quantity of lipid for biodiesel production.

Effect of different plant species on nutrient removal and rhizospheric microorganisms distribution in horizontal-flow constructed wetlands

Three macrophyte species, Phragmites australis, Arundo donax L., and Typha latifolia L. have been separately grown in a horizontal-flow (HF) constructed wetland (CW) fed with domestic wastewater to investigate effects of plant species on nutrient removal and rhizospheric microorganisms. All the three mesocosms have been in operation for eight months under the loading rates of 1.14 g N m−2 d−1 and 0.014 g P m−2 d−1. Appropriately 34–43% phosphorus (P) was removed in HF CWs, and no distinct difference was found among the plants. In the growing season, A. donax L. removed 31.19 g m−2 of nitrogen (N), followed by P. australis (29.96 g m−2), both of which were significantly higher than T. latifolia L. (7.21 g m−2). Depending on the species, plants absorbed 1.73–7.15% of the overall N, and 0.06–0.56% of the P input. At least 10 common dominant microorganisms were found in the rhizosphere of all the three plants, and 6 of the 10 kinds of bacteria had close relationship with denitrifying bacteria, implying that denitrifiers were dominant microorganism distributed in rhizosphere of wetland plants.

The effects of combined agricultural phytohormones on the growth, carbon partitioning and cell morphology of two screened algae

Applying phytohormones has been considered a promising way to increase lipid productivity of microalgae recently. Eight dosages of auxin phytohormones were tested to exploit the effects and mechanism of such stimulants on microalgae. The optimal one was 20mgL-1, leading to an increase in biomass concentration of 59.3% for Scenedesmus sp. SDEC-8 and 76.6% for Chlorella sorokiniana SDEC-18, meanwhile the lipid content rose from 18.74% to 56.17% (SDEC-8) and from 19.69% to 55.76% (SDEC-18). Proton pumps were activated by the stimulants, causing excretion of H+, which resulted in pH decline and a favorable condition for growth. Pigments changes implied that hormones strengthened the dark reactions of photosynthesis. Auxin addition led to a 3μm increase in diameter for C. sorokiniana SDEC-18 and altered the cellular pattern of Scenedesmus sp. SDEC-8, which improved the cells elongation. Therefore, supplement of auxin phytohormones simultaneously increased the viability and lipid production of microalgae.

The effect of algae species on the bioelectricity and biodiesel generation through open-air cathode microbial fuel cell with kitchen waste anaerobically digested effluent as substrate

Five strains algae (Golenkinia sp. SDEC-16, Chlorella vulgaris, Selenastrum capricornutum, Scenedesmus SDEC-8 and Scenedesmus SDEC-13) were screened as an effective way to promote recover electricity from MFC for kitchen waste anaerobically digested effluent (KWADE) treatment. The highest OCV, power density, biomass concentration and total lipid content were obtained with Golenkinia sp. SDEC-16 as the co-inoculum, which were 170mV, 6255mWm(-3), 325mgL(-1) and 38%, respectively. Characteristics of the organics in KWADE were analyzed, and the result showed that the hydrophilic and acidic fractions were more readily degraded, compared to the neutral fractions during the operation. Maximum COD and TN removal efficiency were 43.59% and 37.39% when inoculated with Golenkinia sp. SDEC-16, which were roughly 3.22 and 3.04 times higher than that of S. capricornutum. This study demonstrated that Golenkinia sp. SDEC-16 was a promising species for bioelectricity generation, lipid production and KWADE treatment.

Mutual facilitations of food waste treatment, microbial fuel cell bioelectricity generation and Chlorella vulgaris lipid production.

Food waste contains large amount of organic matter that may be troublesome for handing, storage and transportation. A microbial fuel cell (MFC) was successfully constructed with different inoculum densities of Chlorella vulgaris for promoting food waste treatment. Maximum COD removal efficiency was registered with 44% and 25 g CODL(-1)d(-1) of substrate degradation rate when inoculated with the optimal initial density (150 mg L(-1)) of C. vulgaris, which were 2.9 times and 3.1 times higher than that of the abiotic cathode. With the optimum inoculum density of C. vulgaris, the highest open circuit voltage, working voltage and power density of MFC were 260 mV, 170 mV and 19151 mW m(-3), respectively. Besides the high biodiesel quality, promoted by MFC stimulation the biomass productivity and highest total lipid content of C. vulgaris were 207 mg L(-1)d(-1) and 31%, which were roughly 2.7 times and 1.2 times higher than the control group.

Phytohormone addition coupled with nitrogen depletion almost tripled the lipid productivities in two algae

Nitrogen starvation has been an effective method to enhance the lipid content in microalgae, but low biomass means the method is far from large-scale application. In this study a combination of phytohormones, indolebutyric acid (IBA) and naphthylacetic acid (NAA), was used to verify whether phytohormones can assist two microalgae, Scenedesmus SDEC-8 and Chlorella sorokiniana SDEC-18, to resist nitrogen depletion, and achieve satisfactory biomass and lipid productivity. The two algae grew poorly but accumulated high lipid concentrations under nitrogen-depleted condition without phytohormones. However, phytohormone addition maintained the biomass concentration, and furthermore yielded lipid productivities (SDEC-8: 26.7mg/L/d, SDEC-18: 25.9mg/L/d) almost 3 times as high as those in BG11. The oxidative damage caused by nitrogen depletion could be alleviated by phytohormones. The investigation demonstrated that phytohormone supplementation simultaneously improved lipid accumulation and maintained growth of microalgae, while also optimizing the biodiesel properties compared with the tactic of nitrogen depletion alone.

Salinity-induced cellular cross-talk in carbon partitioning reveals starch-to-lipid biosynthesis switching in low-starch freshwater algae

Salinity stress has been verified to be a successful approach to enhance lipid production in high-starch marine algae, and salinity-induced carbon flow switching has been proposed as an algal response specific to brackish water. With the aim of testing this assumption, Chlorella sorokiniana SDEC-18, a low-starch freshwater alga, was grown in BG11 medium with NaCl addition at various concentrations (0, 2, 5, 10, 20, and 30 g/L). The results showed that salinity stress promoted carbon redistribution and starch conversion to lipid. The most desirable lipid productivity of 19.66 mg/L·d occurred in the medium with 20 g/L NaCl, about 2.16 times as high as that in the BG11 medium control. Moreover, microalgae with salinity stress were able to produce biodiesel with a more suitable cloud point, due to a decrease in the saturated fatty acid content. This therefore confirms that low-starch freshwater microalgae can also carry out salinity-induced carbon flow switching.

Features of Golenkinia sp. and microbial fuel cells used for the treatment of anaerobically digested effluent from kitchen waste at different dilutions

The aim of this work was to study Golenkinia sp. and microbial fuel cells (MFCs) for the treatment of anaerobically digested effluent from kitchen waste (ADE-KW) with different dilution factors. A dual-chamber MFC was fabricated for treating ADE-KW in the two chambers of the MFC and harvesting Golenkinia sp. All the anodic TN was removed more than 80%. COD removal efficiency increased from 48.2% to 76% when the dilution factor increased from 1 to 4. Maximum COD and TN removal rates were 3.56 and 3.71mg·L-1·h-1 when ADE-KW was treated without dilution in the anodic chamber. All the cathodic TN and TP removal efficiencies were approximately 90%. The highest open circuit voltage (OCV) and power density were approximately 400mV and 400mW when ADE-KW was treated directly (undiluted) in the MFC, with the highest biomass and total lipid content production of Golenkinia sp. in the cathodic chamber.

Using a tubular photosynthetic microbial fuel cell to treat anaerobically digested effluent from kitchen waste: Mechanisms of organics and ammonium removal

Anaerobically digested effluent from kitchen waste (ADE-KW) was used herein as the substrate of a tubular photosynthetic microbial fuel cell (PMFC) for power production, and also, after being diluted, as a medium for cultivation of algae in the cathodic chamber. Adding 3 mg/L phosphorus to the catholyte could efficiently enhance the algal growth and the PMFC performance. About 0.94 g/L algal biomass and 0.57 kWh/m3-ADE-KW bioelectricity were obtained from the PMFC. Soluble microbial byproduct-like material and aromatic proteins were the dominant organics in the ADE-KW, which were readily degradable in the system. About 79% of the 1550 mg/L ammonium in the anolyte transferred to the catholyte through the cation exchange membrane. The ammonium was removed mainly as electron acceptors at the cathode after being oxidized by oxygen, whereas algal assimilation only account for about 14.6% of the overall nitrogen.

The effects of algal extracellular substances on algal growth, metabolism and long-term medium recycle, and inhibition alleviation through ultrasonication

The algal extracellular substances (AESs), mainly excreted in the lag and stationary phases, inhibited the algal growth and culture recycle. The AESs consisted of protein-like substances and saccharides, which restrained the algal lipid and protein biosynthesis. Moreover, the increasing reactive oxygen species and anti-oxidative enzymes caused by AESs led to the oxidative damage and suppressed the cell activity. The AESs affected the cells through two possible ways: one is the AESs adhered to the cell surfaces; another is the cells yielded signal molecules in response to the AESs. Fortunately, the ultrasound degraded the AESs into small molecules, which clearly alleviated the limitation and recovered the algal biomass and metabolism. This study demonstrated that ultrasonication is a promising way to alleviate the AESs, which facilitating the medium recycle for long-term continuous microalgae production.