BackgroundMicroalgae provide an excellent platform for the production of high-value-products and are increasingly being recognised as a promising production system for biomass, animal feeds and renewable fuels.ResultsHere, we describe an automated screen, to enable high-throughput optimisation of 12 nutrients for microalgae production. Its miniaturised 1,728 multiwell format allows multiple microalgae strains to be simultaneously screened using a two-step process. Step 1 optimises the primary elements nitrogen and phosphorous. Step 2 uses Box-Behnken analysis to define the highest growth rates within the large multidimensional space tested (Ca, Mg, Fe, Mn, Zn, Cu, B, Se, V, Si) at three levels (−1, 0, 1). The highest specific growth rates and maximum OD750 values provide a measure for continuous and batch culture.ConclusionThe screen identified the main nutrient effects on growth, pairwise nutrient interactions (for example, Ca-Mg) and the best production conditions of the sampled statistical space providing the basis for a targeted full factorial screen to assist with optimisation of algae production.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0238-7) contains supplementary material, which is available to authorized users.

Single cell green algae (microalgae) are rapidly emerging as a platform for the production of sustainable fuels. Solar-driven H2 production from H2O theoretically provides the highest-efficiency route to fuel production in microalgae. This is because the H2-producing hydrogenase (HYDA) is directly coupled to the photosynthetic electron transport chain, thereby eliminating downstream energetic losses associated with the synthesis of carbohydrate and oils (feedstocks for methane, ethanol and oil-based fuels). Here we report the simultaneous knock-down of three light-harvesting complex proteins (LHCMB1, 2 and 3) in the high H2-producing Chlamydomonas reinhardtii mutant Stm6Glc4 using an RNAi triple knock-down strategy. The resultant Stm6Glc4L01 mutant exhibited a light green phenotype, reduced expression of LHCBM1 (20.6% ±0.27%), LHCBM2 (81.2% ±0.037%) and LHCBM3 (41.4% ±0.05%) compared to 100% control levels, and improved light to H2 (180%) and biomass (165%) conversion efficiencies. The improved H2 production efficiency was achieved at increased solar flux densities (450 instead of ∼100 µE m−2 s−1) and high cell densities which are best suited for microalgae production as light is ideally the limiting factor. Our data suggests that the overall improved photon-to-H2 conversion efficiency is due to: 1) reduced loss of absorbed energy by non-photochemical quenching (fluorescence and heat losses) near the photobioreactor surface; 2) improved light distribution in the reactor; 3) reduced photoinhibition; 4) early onset of HYDA expression and 5) reduction of O2-induced inhibition of HYDA. The Stm6Glc4L01 phenotype therefore provides important insights for the development of high-efficiency photobiological H2 production systems.

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This work presents the viability of biomass waste watermelon (Citrullus lanatus) rinds (WMR) as low-cost adsorbent for the removal of methylene blue (MB) from aqueous solution. The physicochemical properties of WMR were characterized using instrumental analyses such as CHNS-O analyzer, Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and point of zero charge (pHpzc) analysis. The kinetic data revealed that the present system obeyed pseudo-second-order kinetic model. The equilibrium data were found to better fit with the Langmuir isotherm model than the Freundlich model. The adsorption capacity of WMR for MB was 188.68 mg/g at 303 K. The thermodynamic adsorption parameters, namely standard enthalpy (H°), standard entropy (S°) and standard free energy (G°) showed that the adsorption of MB onto WMR was spontaneous and exothermic under the experimented conditions. These results indicate that the WMR can be feasibly employed for the eradication of MB from aqueous solution.

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Trigonella foenum-graecum (TFG) is a significant leguminous plant with diverse pharmacological effects. However, the resistant character of this plant accounts for significant difficulties in vitro multiplication, justifying the necessity to try new techniques for in vitro propagation of this plant. Hence, this study reports the effects of BAP, NAA, and 2,4-D on in vitro callus formation of seeds. The toxicity properties of seeds, plant, and callus aqueous extracts of TFG were measured by brine shrimp assay (BSA). Callus index, frequency of callus, callus weight, and morphology of callus were recorded after 30 days of culture. No callus formation was observed in the absence of plant growth regulators. The maximum callus formation observed in the MS media containing 1.0 mg/l 2,4-D, the highest mean of the callus index (52±9.5) with 100% frequency and callus yield (0.52±0.08 g) in 30 days of culture. The highest mean of callus index (37±0 4.05) for combination hormones with 100% callusing and yield (0.37±0.02 g) in 30 days of culture by 1.0 mg/l BAA with 0.5 mg/l NAA. Seeds extract of TFG showed the highest toxicity (954.99 µg/ml), aqueous plant extract (1237.98 µg/ml), and aqueous callus extract (1801 µg/ml) from BSA. Comparing individual hormones, the highest amount of callus in TFG can be yielded 2,4-D hormone alone, and a combination of BAP and NAA can yield 100% callus.

In this study, co-gasification of palm kernel shell (PKS) and low-rank Malaysian coal (MB) was carried out in a fixed bed reactor. For the pretreated samples, PKS was torrefied at 270C (PKSTo) and MB was preheated at 250C (MBPr) for 1 h, respectively, prior to co-gasification at 767C, with a biomass blending ratio of 52% and a steam flow rate of 55 mL/min. The effect of different blending combinations was investigated towards product yields, namely gas, tar, char and gases composition. The co-gasification on both pretreated (PKSTo/MBPr) and catalyst-pretreated (Cat-PKSTo/MBPr) produced a greater gas yield, with lesser tar and char yield than both untreated PKS and MB (PKSUn/MBUn) and pretreated PKS and untreated MB (PKSTo/MBUn). The PKSTo/MBPr was found to enhance the H2 production by 63.9% and 41% than PKSUn/MBUn and PKSTo/MBUn, respectively, at 45 min of reaction time. Thus, the pretreatment on both samples had a significant impact on the distribution and composition of product yields during co-gasification. As a conclusion, the pretreated sample, which has been upgraded on characteristics such as higher carbon and lower oxygen content than the untreated sample was revealed to enhance gas yield and H2 production during co-gasification.

a b s t r a c tPomegranate (Punica Granatum) peels were utilized as precursors to prepare mesoporous activated carbon (PPAC) via H 3 PO 4 -activation method. The surface characterization of PPAC was achieved using Fourier Transform Infrared (FTIR), Scanning Electron Microscopy (SEM), N 2 adsorption/ desorption, X-Ray Diffraction (XRD), and the point of zero charge (pH PZC ) method. It was found that PPAC a large surface area and total pore volume corresponded to 1280.45 m²/g and 1.343 cm 3 /g, respectively. The adsorption properties of PPAC with methylene blue (MB) was conducted at different adsorbent dose (0.2-3 g/L), solution pH (3-11), initial dye concentrations (50 mg/L-400 mg/L), contact time (0-135 min) using batch mode operation. The kinetic uptake profiles are well described by the pseudo-second-order model, while the Langmuir model describes the adsorption behaviour at equilibrium. The maximum adsorption capacity of PPAC with methylene blue was 384.61 mg/g at 303 K. Various thermodynamic parameters such as standard enthalpy (∆H°), standard entropy (∆S°) and standard free energy (∆G°) showed that the adsorption of MB onto PPAC was favourable and endothermic in nature.