Dry anaerobic digestion of high solids content dairy manure at high organic loading rates in psychrophilic sequence batch reactor

Cow manure with bedding is renewable organic biomass available around the year on dairy farms. Developing efficient and cost-effective psychrophilic dry anaerobic digestion (PDAD) processes could contribute to solving farm-related environmental, energy, and manure management problems in cold-climate regions. This study was to increase the organic loading rate (OLR), fed to a novel psychrophilic (20 °C) dry anaerobic digestion of 27 % total solid dairy manure (cow feces and wheat straw) in sequence batch reactor (PDAD-SBR), by 133 to 160 %. The PDAD-SBR process operated at treatment cycle length of 21 days and OLR of 7.0 and 8.0 g total chemical oxygen demand (TCOD)?kg^?1 inoculum day^?1 (5.2?±?0.1 and 5.8?±?0.0 g volatile solids (VS)?kg^?1 inoculum day^?1) for four successive cycles (84 days) produced average specific methane yields (SMYs) of 147.1?±?17.2 and 143.2?±?11.7 normalized liters (NL)?CH₄?kg^?1 VS fed, respectively. PDAD of cow feces and wheat straw is possible with VS-based inoculum-to-substrate ratio of 1.45 at OLR of 8.0 g TCOD kg^?1 inoculum day^?1. Hydrolysis was the limiting step reaction. The VS removal averaged around 57.4?±?0.5 and 60.5?±?5.7 % at OLR 7.0 and 8.0 g TCOD kg^?1 inoculum day^?1, respectively.     

Exposure to aflatoxin B<Subscript>1</Subscript> in Thailand by consumption of brown and color rice

This study assessed the aflatoxin B₁ (AFB₁) intake of the Thai population through consumption of contaminated brown and color rice. A total of 240 rice samples from two harvesting periods were collected in June/July 2012 (period I) and in December 2012/January 2013 (period II) and analyzed for AFB₁ by HPLC with fluorescence detection (limit of detection (LOD)?=?0.093 ng/g). Exposure assessment was based on AFB₁ levels in rice and food intake data for rice according to Thai National Consumption. Frequency and levels of AFB₁ were higher in period I (59 %, <LOD?=?26.61 μg kg^?1) than in period II (10 %, <LOD?=?3.51 μg kg^?1). Only one sample exceeded the Thai standard limit for total aflatoxin of 20 μg kg^?1, but 12 out of 240 rice samples exceeded the European Union maximum level for AFB₁ of 2 μg kg^?1. The data showed that the quality and safety of Thai rice largely comply with the requirement for both exports and domestic consumption. According to the Thai National Consumption data, the estimated AFB₁ intake via rice consumption in period I and period II was 0.80 and 0.12 μg kg^?1 bw day^?1, respectively. The potential risk for cancer, based on the recommendation of the JECFA, was estimated to be 0.011 person/year/100,000 people at a mean consumption. Although the risk via consumption of Thai rice seems to be low, the maximum levels of AFB₁ in this staple food suggest that careful monitoring and surveillance of AFB₁ contamination in rice is essential to ensure the safety of rice.     

A 7-day oral supplementation with branched-chain amino acids was ineffective to prevent muscle damage during a marathon

The aim of this study was to determine the effectiveness of a 7-day oral supplementation with branched-chain amino acids (BCAA) to prevent muscle damage during a marathon. Forty-six experienced runners were randomly divided into two groups, one with BCAA supplementation (n = 25, supplemented with 5 g day^?1 of powdered 1:0.5:0.5 leucine:isoleucine:valine, during the 7 days prior to the competition) and the other as a control group (n = 21, supplemented with an isocaloric placebo). Before the marathon race and within 3 min of finishing, leg muscle power was measured with a maximal countermovement jump and a urine sample was obtained. During the race, running pace was measured by means of a time-chip. Myoglobin concentration was determined in the urine samples as an indirect marker of muscle damage. A visual analog scale (0–10 points) was used to assess leg muscle pain during the race. In the BCAA group, the mean running pace during the marathon was similar to the control group (3.3 ± 0.4 vs. 3.3 ± 0.5 m s^?1, respectively, 0.98). The pre- to post-race reduction in muscle power was similar in both BCAA and control groups (?23.0 ± 16.1 vs. ?17.3 ± 13.8 %, P = 0.13). Post-race urine myoglobin concentration was similar in both BCAA and control groups (5.4 ± 7.5 vs. 4.5 ± 8.6 μg mL^?1, P = 0.70). Finally, there were no differences between groups in the perceived muscle pain during the race (6 ± 1 vs. 5 ± 1 points, P = 0.80). A 7-day supplementation of BCAA (5 g day^?1) did not increase the running performance during a marathon. Furthermore, BCAA supplementation was ineffective to prevent muscle power loss, muscle damage or perceived muscle pain during a marathon race.     

Performance and tissue fatty acid profiles in veal calves fed diets supplemented with conjugated linoleic acids

Three groups of six calves each were fed a milk replacer at 0.8 kg and a starter concentrate ad libitum. Calves of the control group received the basal diet supplemented with rapeseed oil at 10 g per kg of feed solids. Calves of treatment groups were fed diets supplemented with a synthetically produced oil containing 62.3% methyl esters of CLA. The CLA-oil was added to milk at expense of rapeseed oil and fed at 5 and 10 g · kg^?1 feed solids for 63 days. Calves were slaughtered at 115 days of age. There was no significant effect of CLA on growth, intake of starter, feed conversion, chemical composition of meat and its oxidative stability. Dietary supplementation with CLA at 10 g · kg^?1 significantly increased CLA content in m. longissimus dorsi (MLD) from 5.6 to 19.3 mg · 100 g^?1, in liver from 13.1 to 68.8 mg · 100 g^?1, and in perirenal fat from 0.37 to 3.17 g · 100 g^?1. Dietary CLA decreased the ratio of cis-9, trans-11 and trans-10, cis-12 isomers of CLA in tissues, concentration of monounsaturated fatty acids in the MLD and fat, as well as the concentration of fatty acids with 20 and 22 carbon atoms. It can be concluded that in veal calves unprotected CLA apparently escaped ruminal hydrogenation, but was preferentially incorporated into depot fat.     

Suggestion of GLYAT gene underlying variation of bone size and body lean mass as revealed by a bivariate genome-wide association study

Bone and muscle, two major tissue types of musculoskeletal system, have strong genetic determination. Abnormality in bone and/or muscle may cause musculoskeletal diseases such as osteoporosis and sarcopenia. Bone size phenotypes (BSPs), such as hip bone size (HBS), appendicular bone size (ABS), are genetically correlated with body lean mass (mainly muscle mass). However, the specific genes shared by these phenotypes are largely unknown. In this study, we aimed to identify the specific genes with pleiotropic effects on BSPs and appendicular lean mass (ALM). We performed a bivariate genome-wide association study (GWAS) by analyzing ~690,000 SNPs in 1,627 unrelated Han Chinese adults (802 males and 825 females) followed by a replication study in 2,286 unrelated US Caucasians (558 males and 1,728 females). We identified 14 interesting single nucleotide polymorphisms (SNPs) that may contribute to variation of both BSPs and ALM, with p values <10^?6 in discovery stage. Among them, the association of three SNPs (rs2507838, rs7116722, and rs11826261) in/near GLYAT (glycine-N-acyltransferase) gene was replicated in US Caucasians, with p values ranging from 1.89 × 10^?3 to 3.71 × 10^?4 for ALM–ABS, from 5.14 × 10^?3 to 1.11 × 10^?2 for ALM–HBS, respectively. Meta-analyses yielded stronger association signals for rs2507838, rs7116722, and rs11826261, with pooled p values of 1.68 × 10^?8, 7.94 × 10^?8, 6.80 × 10^?8 for ALB–ABS and 1.22 × 10^?4, 9.85 × 10^?5, 3.96 × 10^?4 for ALM–HBS, respectively. Haplotype allele ATA based on these three SNPs was also associated with ALM–HBS and ALM–ABS in both discovery and replication samples. Interestingly, GLYAT was previously found to be essential to glucose metabolism and energy metabolism, suggesting the gene’s dual role in both bone development and muscle growth. Our findings, together with the prior biological evidence, suggest the importance of GLYAT gene in co-regulation of bone phenotypes and body lean mass.     

Occurrence and risk assessment of organophosphorus pesticide residues in Chinese tea

Tea is the second widely consumed beverage next to water. Tea drinking is one of the important pathways for human exposure of organonphosphorus pesticide. Consequently, incidence of organonphosphorus pesticide residues and risk assessment should be clear. In this study, the level of organonphosphorus pesticide residues in 810 Chinese teas manufactured between 2010–2013 was investigated using gas chromatography coupled with tandem mass spectrometry and a flame photometric detector. Incidence of organonphosphorus pesticide residues occurred with a frequency of 29% and the average concentration of 93 μg kg^?1. The residue levels varied from tea types, sale spots, and production area. Chlorpyrifos, isocarbophos, and triazophos were the only three organonphosphorus pesticides with detectable residues, and the detectable rates were 13.0%, 13.6%, and 17.4%, respectively. The corresponding average daily intake of chlorpyrifos, isocarbophos, and triazophos by tea drinking was 0.000083 μg kg^?1 bw day^?1, 0.0036 μg kg^?1 bw day^?1, and 0.0022 μg kg^?1 bw day^?1. These results showed that the total hazard quotient of organonphosphorus pesticide pesticides from tea drinking was less than 0.02 and that the tea-drinking originated organonphosphorus pesticide exposure had a little adverse health effect for human being.     

Zinc seed coating improves the growth,grain yield and grain biofortification of bread wheat

This study, comprising three independent experiments, was conducted to optimize the zinc (Zn) application through seed coating for improving the productivity and grain biofortification of wheat. Experiment 1 was conducted in petri plates, while experiment 2 was conducted in sand-filled pots to optimize the Zn seed coating using two sources (ZnSO₄, ZnCl₂) of Zn. In the first two experiments, seeds of two wheat cultivars Lasani-2008 and Faisalabad-2008 were coated with 0.25, 0.50, 0.75, 1.00, 1.25, 1.50, 1.75 and 2.00 g Zn kg^?1 seed using ZnSO₄ and ZnCl₂ as Zn sources. The results of experiment I revealed that seed coating with 1.25 and 1.50 g Zn kg^?1 seed using both sources of Zn improved the seedling emergence. However, seed coated with 1.25 and 1.50 g Zn kg^?1 seed using ZnSO₄ was better regarding improvement in seedling growth and seedling dry weight. The results of the second experiment indicated that seed coated with 1.25 and 1.50 g Zn kg^?1 seed using ZnSO₄ improved the seedling emergence and seedling growth of tested wheat cultivars. However, seed coating beyond 1.5 g Zn kg^?1 seed using either Zn source suppressed the seedling emergence. Third experiment was carried out in glass house in soil-filled earthen pots. Seeds of both wheat cultivars were coated with pre-optimized treatments (1.25, 1.50 g Zn kg^?1 seed) using both Zn sources. Seed coating with all treatments of ZnSO₄ and seed coating with 1.25 g Zn kg^?1 seed using ZnCl₂ improved the seedling emergence and yield-related traits of wheat cultivars. Seed coating with 1.25 g Zn kg^?1 seed also improved the chlorophyll a and b contents. Maximum straw Zn contents, before and after anthesis, were recorded from seed coated with 1.5 g Zn kg^?1 seed using either Zn source. Increase in grain yield from seed coating followed the sequence 1.25 g Zn kg^?1 seed (ZnSO₄) >1.25 g Zn kg^?1 seed (ZnCl₂) >1.5 g Zn kg^?1 seed (ZnSO₄). However, increase in grain Zn contents from seed coated was 1.5 g Zn kg^?1 seed (ZnCl₂) >1.25 and 1.5 g Zn kg^?1 seed (ZnCl₂, ZnSO₄) >1.25 g Zn kg^?1 seed (ZnSO₄). Seed coating with Zn increased the grain Zn contents from 21 to 35 %, while 33–55 % improvement in grain yield was recorded. In conclusion, wheat seeds may be coated with 1.25 g Zn kg^?1 seed using either source of Zn for improving the grain yield and grain Zn biofortification.     

The effects of molybdenum and boron on the rhizosphere microorganisms and soil enzyme activities of soybean

This study examined the effects of molybdenum (Mo) and boron (B) on the rhizosphere microorganisms and the soil enzyme activities of soybean. The soybeans were treated with seven different Mo and B supplements (control: without Mo and B) Mo1 (0.0185 g kg^?1), B1 (0.08 g kg^?1), Mo1 + B1 (0.0185 + 0.08 g kg^?1), Mo2 (0.185 g kg^?1), B2 (0.3 g kg^?1) and Mo2 + B2 (0.185 + 0.3 g kg^?1) throughout the plants’ four growth stages. The results showed that Mo, B, and combined Mo and B treatments increased the soil microbial populations, stimulated the rhizosphere metabolisms, and improved the soil enzyme activities. These stimulatory effects varied in intensity among the treatment groups. The Mo and B combination treatments were more beneficial for the soybean rhizosphere soil than that of Mo-only or the B-only treatments, which suggests that the two elements have complementary functions in the biological processes of the soybean rhizosphere.     

Assessment of Human Health Risks of Consumption of Cadmium Contaminated Cultured Oysters

With farmed British Columbia (BC) oysters containing higher cadmium concentrations than wild oysters, long-term exposure to cadmium through consumption of oysters has the potential to cause health risks. This study reports on a risk assessment for cadmium intake resulting from the consumption of BC-cultured oyster. The study concludes that Health Canada's current recommended BC-cultured oyster consumption rate for Canadians of 12 oysters per month exceeds the Agency for Toxic Substances and Disease Registry chronic oral minimal risk levels (MRL) of 0.2 μ g·kg^{? 1}·day^{? 1} by approximately 4-to 5-fold and reaches the Food and Agriculture Organization/World Health Organization (FAP/WHO) reference dose of 1 μg·kg^?1·day^?1 for cadmium consumption for Canadians. This suggests that although the current recommended maximum oyster consumption rates is consistent with the FAO/WHO and U.S. Environmental Protection Agency limits for acceptable risk, it leaves little or no room for error or uncertainty. This is noteworthy as recent studies demonstrate toxicological effects at cadmium intakes of 0.43 to 0.71 μ gCd·kg^?1·day^?1. This study indicates that a lower maximum BC-cultured oyster rate should be considered, particularly for high risk groups, including women with low iron stores, people with renal impairment, smokers, children, and indigenous people who consume organ meats of games and wildlife other than shellfish.     

A quantitative study of eicosapentaenoic acid (EPA) production by Nannochloropsis gaditana for aquaculture as a function of dilution rate,temperature and average irradiance

Different pilot-scale outdoor photobioreactors using medium recycling were operated in a greenhouse under different environmental conditions and the growth rates (0.1 to 0.5 day^?1) obtained evaluated in order to compare them with traditional systems used in aquaculture. The annualized volumetric growth rate for Nannochloropsis gaditana was 0.26 g l^?1 day^?1 (peak 0.4 g l^?1 day^?1) at 0.4 day^?1 in a 5-cm wide flat-panel bioreactor (FP-PBR). The biomass productivity achieved in this reactor was 10-fold higher than in traditional reactors, reaching values of 28 % and 45 % dry weight (d.w.) of lipids and proteins, respectively, with a 4.3 % (d.w.) content of eicosapentaenoic acid (EPA). A model for predicting EPA productivity from N. gaditana cultures that takes into account the existence of photolimitation and photoinhibition of growth under outdoor conditions is presented. The effect of temperature and average irradiance on EPA content is also studied. The maximum EPA productivity attained is 30 mg l^?1 day^?1.     

The transgenic expression of human follistatin-344 increases skeletal muscle mass in pigs

Follistatin (FST), which was first found in the follicles of cattle and pigs, has been shown to be an essential regulator for muscle development. Mice that were genetically engineered to overexpress Fst specifically in muscle had at least twice the amount of skeletal muscle mass as controls; these findings are similar to earlier results obtained in myostatin-knockout mice. However, the role of follistatin in skeletal muscle development has yet to be clarified in livestock. Here, we describe transgenic Duroc pigs that exogenously express Fst specifically in muscle tissue. The transgenic pigs exhibited an increased proportion of skeletal muscle and a reduced proportion of body fat that were similar to those reported in myostatin-null cattle. The lean percentage of lean meat was significantly higher in the F1 generation of TG pigs (72.95 ± 1.0 %) than in WT pigs (69.18 ± 0.97 %) (N = 16, P < 0.05). Myofiber hypertrophy was also observed in the longissimus dorsi of transgenic pigs, possibly contributing to the increased skeletal muscle mass. Western blot analysis showed a significantly reduced level of Smad2 phosphorylation and an increased level of Akt^S473 phosphorylation in the skeletal muscle tissue of the transgenic pigs. Moreover, no cardiac muscle hypertrophy or reproductive abnormality was observed. These findings indicate that muscle-specific Fst overexpression in pigs enhances skeletal muscle growth, at least partly due to myofiber hypertrophy and providing a promising approach to increase muscle mass in pigs and other livestock.     

Improving mass transfer in an inclined tubular photobioreactor

The mass transfer and hydrodynamics of two outdoor tubular photobioreactor designs were compared, a Tredici-design near-horizontal tubular photobioreactor (NHTR) and an enhanced version of this reactor (ENHTR), for the purpose of improving algal growth via improved hydrodynamics. The enhancements included addition of vertical bubble columns at the sparger end and a larger degasser with a diffuser. Gas-liquid mass transfer and other performance measures were assessed for a range of gas sparging rates. The ENHTR modifications proved to be very successful, increasing oxygen stripping and carbon dioxide dissolution by 120–220 % and 0–50 %, respectively. There was an increase in axial mixing and a fourfold decrease in total mixing time. Experiments were conducted to determine that approximately 50 % of the mass transfer occurred in the vertical bubble columns, while 85–90 % of the mass transfer in the near-horizontal tubes occurred in the lower half of the tubes. These improvements can lead to increased algae productivity depending upon culture-specific parameters. The theoretical maximum productivity of a hypothetical algal culture would be 1.6 g m^?2 h^?1 in the NHTR, and we have previously achieved a maximum of 1.5 g m^?2 h^?1 growing Arthrospira at densities up to 7.5 g L^?1 in this reactor. Due to enhanced mass transfer in the ENHTR, the predicted maximum productivity should increase to 4.75 g m^?2 h^?1. The potential for further improvements in productivity due to various additional enhancements is described.     

Changes in amino acid composition in the tissues of African catfish (Clarias gariepinus) as a consequence of dietary L-carnitine supplements

A study was undertaken to examine the effect of different amounts of dietary lysine (13 and 21 g kg^?1 diet), lipid (80 and 160 g kg^?1 diet) and L ‐carnitine (0.2 and 1.0 g kg^?1 diet) on growth performance, proximate composition and amino acid metabolism of the African catfish (Clarias gariepinus). Juvenile African catfish (23 ± 1.5 g/fish) were stocked into 70‐L aquaria (16 aquaria, 28 fish/aquarium) connected to a recirculation system during a maximum period of 74 days. All groups were fed at a level of 24 g kg^?0.8 day^?1 in an experiment run at pair feeding. Animals receiving 1.0 g carnitine accumulated up to six times more carnitine in their tissues than animals receiving 0.2 g (P < 0.05). Acyl‐carnitine and free L ‐carnitine levels increased in the whole body and in tissues. Dietary L ‐carnitine supplements increased protein‐to‐fat ratios in the body, but did not affect growth rate. Protein‐to‐fat ratios were only affected when the biosynthesis capacity of L ‐carnitine was restricted due to low lysine levels and when there was a shortage of dietary fat. When lysine was offered at 21 g kg^?1 feed, dietary L ‐carnitine supplements did not affect the amino acid concentrations of body tissues. Dietary L ‐carnitine supplements raised the concentration of glutamic acid > aspartic acid > glycine > alanine > arginine > serine > threonine in skeletal muscle tissue (P < 0.05). Total amino acid concentration in muscle and liver tissues (dry‐matter basis) increased from 506 to 564 and from 138 to 166 mg g^?1, respectively, when diets were offered with high L ‐carnitine, low lysine and low fat levels. These data suggest that dietary L ‐carnitine supplementation may increase fatty acid oxidation and possibly decrease amino acid combustion for energy.     

Taurine supplementation decreases oxidative stress in skeletal muscle after eccentric exercise

Infrequent exercise, typically involving eccentric actions, has been shown to cause oxidative stress and to damage muscle tissue. High taurine levels are present in skeletal muscle and may play a role in cellular defences against free radical‐mediated damage. This study investigates the effects of taurine supplementation on oxidative stress biomarkers after eccentric exercise (EE). Twenty‐four male rats were divided into the following groups (n = 6): control; EE; EE plus taurine (EE + Taurine); EE plus saline (EE + Saline). Taurine was administered as a 1‐ml 300 mg kg^?1 per body weight (BW) day^?1 solution in water by gavage, for 15 consecutive days. Starting on the 14th day of supplementation, the animals were submitted to one 90‐min downhill run session and constant velocity of 1·0 km h^?1. Forty‐eight hours after the exercise session, the animals were killed and the quadriceps muscles were surgically removed. Production of superoxide anion, creatine kinase (CK) levels, lipoperoxidation, carbonylation, total thiol content and antioxidant enzyme were analysed. Taurine supplementation was found to decrease superoxide radical production, CK, lipoperoxidation and carbonylation levels and increased total thiol content in skeletal muscle, but it did not affect antioxidant enzyme activity after EE. The present study suggests that taurine affects skeletal muscle contraction by decreasing oxidative stress, in association with decreased superoxide radical production. Copyright © 2010 John Wiley & Sons, Ltd.     

Non Linear Weight Gain with Long Term Overfeeding in Man

This study deals with the pattern of body weight gain during an overfeeding period with a constant energy intake, in order to assess whether total daily energy expenditure (TEE) increased with body weight and thus could account for the progressive slow down in body weight gain over time. Twenty-four young adult males (12 pairs of identical twins) were overfed by 4.2 MJ per day, six days a week, for a total of 84 days during a 100-day overfeeding period. The total excess amount each man consumed was 353 MJ. It was assumed that, at a given time, the TEE increase (E) was dependent on body weight gain and energy cost (C) was proportional to the daily body weight gain. Results show an exponential increase in body weight, fat free mass, and fat mass (with half-times of 86, 57, and 84 days, respectively) that allows the calculation of E (246 ± 37 kJ*kg^?1 d^?1, mean ± SE) and C (32.3 ± 2.4 MJ kg^?1). Energy expenditure from other sources besides resting metabolic rate, such as physical activity and thermic effect of food, may represent as much as 65% of E. At the beginning of the overfeeding period, almost all the energy surplus was recovered as body substances but this proportion decreased to 60% after 100 days of overfeeding. It is concluded that 1) TEE changes were related to body weight change, 2) about 65% of E were accounted for by physical activity, thermic effect of food, or some other components, and 3) the fraction of the energy surplus stored as body substances decreased with the duration of overfeeding.     

Batch and semi-continuous microalgal TAG production in lab-scale and outdoor photobioreactors

Microalgal triglycerides (TAGs) represent a sustainable feedstock for food, chemical and biofuel industries. The operational strategy (batch, semi-continuous, continuous cultivations) has an impact on the TAG productivity. In this study, semi-continuous (i.e. with fixed harvesting frequency) and batch cultivations were compared on TAG production both at lab-scale and in outdoor cultivations. At lab-scale, the semi-continuous TAG productivity was highest for a cycle time of 2 days (SC1; 0.21 g L^?1 day^?1) and similar to the maximum obtained with the batch (optimal harvest time; 0.23 g L^?1 day^?1). Although TAG content was lower for SC1 (22 %) than for the batch (35 %), higher biomass productivities were obtained with SC1. Outdoors, semi-continuous cultivations were subjected to a lower degree of stress (i.e. higher amount of nitrogen present in the system relative to the given irradiance) compared to lab-scale. This yielded low and similar TAG contents (10–13 %) in the different semi-continuous runs that were outdone by the batch on both TAG content (15–25 %) and productivity (batch, 0.97–2.46 g m^?2 day^?1; semi-continuous, 0.35–0.85 g m^?2 day^?1). The lab-scale experiments showed that semi-continuous strategies, besides leading to similar TAG productivities compared to the batch, could make TAG production cost effective by valorising also non-TAG compounds. However, optimization of outdoor semi-continuous cultivations is still required. For instance, the nitrogen supply and the harvest frequency should be adjusted on the total irradiance. Additionally, future research should focus on recovery metabolism upon nitrogen resupply.     

Energetic evaluation of an internally illuminated photobioreactor for algal cultivation

An annular internally illuminated photobioreatcor (IIPBR) configuration based on the airlift/bubble column principles was developed and validated at an 18 l prototype scale using Scenedemus sp. and Nannochloropsis salina in batch and semi-continuous modes, at constant light supply and constant gas-to-culture volume ratio, but at varying CO₂-to-air ratios. Highest biomass production was recorded at CO₂-to-air ratio of 4% with Scenedesmus sp. and at 1% with Nannochloropsis salina. The energetic performance of this IIPBR was quantified in terms of biomass productivity per unit energy input, P/E (g W^?1 day^?1), considering energy input for illumination and for pneumatic mixing and circulation. Under optimal conditions, the IIPBR evaluated in this study achieved P/E of 1.42 g W^?1 day^?1 for Scenedesmus sp. and P/E of 0.34 g W^?1 day^?1 for Nannochloropsis salina. These P/E values are better than those estimated for airlift and bubble column photobioreactor configurations reported in the literature.     

Enhancing lipid production of the marine diatom Chaetoceros gracilis: synergistic interactions of sodium chloride and silicon

Silicon deficiency is a lipid-promoting stress for many oleaginous diatoms. Literature reports suggest that reduced salinity in seawater, a primary component of which is sodium chloride, may inhibit metabolism of silicon in marine diatoms. We hypothesized that lowering sodium chloride below ocean levels may thus be effective in creating silicon stress and enhancing lipid productivity. We examined the interacting effects of silicon supply (0.05, 0.1, 0.2, and 0.8 mM) and sodium chloride concentration (50, 100, and 400 mM) on growth and lipid production in Chaetoceros gracilis. This was done in batch culture to facilitate the application of severe stress. Low levels of either sodium chloride or silicon resulted in at least 50 % increases in lipid content. The synergy of simultaneous, moderate sodium chloride and silicon stress resulted in lipid content up to 73 % of dry mass and lipid productivity of 1.7 g m^?2 day^?1; with a daily integrated photosynthetic photon flux of 17.3 mol photons m^?2 day^?1, the efficiency of lipid synthesis was thus 0.1 g mol^?1 of photons. Decreased silicon also resulted in a 5 % shift in lipid chain length from C18 to C16 fatty acids. We observed a strong sodium chloride/silicon interaction on total and ash-free dry mass densities that arose because low sodium chloride concentrations were inhibitory to growth, but the inhibition was overcome with excessive silicon supply. This observation suggests that low levels of sodium chloride may have affected metabolism of silicon. The findings of this study can be used to enhance lipid production in oleaginous marine diatoms.     

Key parameters for outdoor biomass production of Scenedesmus obliquus in solar tracked photobioreactors

The biomass productivity of Scenedesmus obliquus was investigated outdoors during all seasons in solar tracked flat panel photobioreactors (PBR) to evaluate key parameters for process optimization. CO₂ was supplied by flue gas from an attached combined block heat and power plant. Waste heat from the power plant was used to heat the culture during winter. The parameters pH, CO₂, and inorganic salt concentrations were automatically adjusted to nonlimiting levels. The optimum biomass concentration increased directly with the photosynthetic active radiation (PAR) from 3 to 5 g dry weight (DW)?L^?1 for a low PAR of 10 mol photons m^?2 day^?1 and high PAR of 40–60 mol photons m^?2 day^?1, respectively. The annual average biomass yield (photosynthetic efficiency) was 0.4?±?0.5 g DW mol^?1 photons. However, biomass yields of 1.5 g DW mol^?1 photons close to the theoretical maximum were obtained at low PAR. The productivity (including the night biomass losses) ranged during all seasons from ?5 up to 30 g DW m^?2 day^?1 with a mean productivity of 9?±?7 g DW m^?2 day^?1. Low night temperatures of the culture medium and elevated day temperatures to the species-specific optimum increased the productivity. Thus, continuous regulation of the biomass concentration and the culture temperature with regard to the fluctuating weather conditions is essential for process optimization of outdoor microalgal production systems in temperate climates.