Low Biomass Yield Research Articles

Tradeoffs between yield, disease incidence and conversion efficiency for selection of hybrid poplar genotypes as bioenergy feedstocks

Lignocellulosic biomass is an alternative source of energy that can reduce our dependency on fossil fuels and limit greenhouse gas emissions. Several techno-economic analyses have consistently shown that all the steps in biomass-to-bioproduct processes needs improvement. Simultaneous assessment of genotypes for multiple productivity characteristics and integrating information across production stages has seldom been the focus of research efforts. To address this gap, we first determined the agronomic performance of 10 poplar genotypes. Differences between genotypes in height, diameter at breast height (DBH), tree mass and yield were consistently observed. Correlation analyses revealed that height and DBH are positively correlated with tree mass and yield, whereas bark content is negatively correlated with tree mass, yield and disease incidence. Four highest-yielding genotypes were subjected to proximate, ultimate, targeted chemical analyses, along with assessment of sugar production by acid hydrolysis and enzymatic saccharification. Despite having only marginal changes in overall chemistry, the genotypes showed differential conversion efficiencies of enzymatic saccharification. Interestingly, the genotype that showed highest cellulose conversion efficiency had the lowest estimated sugar yields due to its low biomass yield, whereas the genotype with lowest conversion efficiency had the highest estimated sugar yields. These results show the importance of integrating information across the stages of biomass production and bioconversion. These results also demonstrate the complexity of biomass feedstock production and the need for future studies to assess whether these tradeoffs can be genetically separated to guide the selection of genotypes that can maximize the overall biomass feedstock production efficiency.

Pigeon pea (Cajanus cajan) fodder cutting management in the Guinea Savanna Agro-Ecological Zone of Ghana

This study evaluated the effect of cutting regime on biomass yield and nutrient composition of pigeon pea (Cajanus cajan (L) Millsp.) fodder in the Guinea Savanna Agro-Ecological Zone of Ghana. Three cutting regimes (12, 16 and 20 Week After Planting [WAP]) in RCBD were imposed on Cajanus cajan at both initial establishment and regrowth. At each harvest, biomass yield was estimated after which samples of the fodder were separated into leaf and stem botanical fractions for chemical composition and in vitro digestibility. Cutting regime significantly affected plant height, number of branches and stem diameter in both the initial establishment and regrowth. Biomass yield was significantly affected by cutting regime in the initial establishment but not the regrowth. The biomass yield was highest in the harvest at 20WAP (6515kgDM/ha) while 12WAP (3175 kg/ha) recorded the lowest biomass yield in the initial establishment. All chemical composition parameters were significantly affected by cutting regime and botanical fractions except hemicellulose in the initial establishment. Cutting regime also significantly affected DM, CP and ash concentrations in the regrowth with botanical fraction significantly (P < 0.05) influencing CP, NDF, ADF and ash. The highest CP was obtained in the leaf fraction harvested at 12 WAP and 20 WAP in the initial establishment and regrowth respectively. Cutting regime, botanical fraction and their interaction were significant in gas produced at 24 h, SCFA and ME in both the initial establishment and regrowth stages. In conclusion, harvest at 20WAP produced the highest biomass yield but lower CP in the initial establishment whiles in the regrowth, harvest at 20WAP produced higher biomass yield, CP and ME.

EFFECTS OF TERMINAL HEAT STRESS AND THEIR RESPONSIVE MECHANISMS IN ELITE WHEAT GENOTYPES: A REVIEW

Wheat is the most important cereal crop in the world that ranks first position in terms of production and trade. In Nepal this is the third most cultivated crop after rice and maize. Various environmental constraints including heat stress have been determined to be a great factor to limit world wheat production. High temperature leaves a devastating impact in wheat production by affecting different stages including germination, plant growth, anthesis and grain filling etc. heat stress also affects photosynthesis process and responsible for the lower biomass yield. Various studies have shown that the reproductive stages of wheat plant are more susceptible to heat stress than vegetative stages. Heat stress hinders germination, reduce plant growth, decrease number of plant population per unit area and causes leaf senescence. Water relation disturbance and oxidative damage to plants are other harmful effects of heat stress in wheat plants. Plant also has tolerance mechanism against such heat induced stresses. Such mechanisms include avoidance against heat stress, production of heat shock protein and antioxidant mechanisms.

Impact of Sowing Dates on Forage Value of Quinoa (Chenopodium quinoa Willd.) Under Semi-arid Conditions

This study was aimed to determine forage value of quinoa at the different sowing dates under semi-arid conditions. Research was conducted according to randomized complete blocks design with three replicates in Harran plain conditions in 2016, Sanliurfa, Turkey. Q-52 Quinoa (Chenopodium quinoa Willd.) variety was used as plant material. In the study 9 different sowing dates were used such as 15 February, 1 March, 15 March, 1 April, 15 April, 1 May, 15 May, 1 June and 15 June. In the research plant height, stem diameter, number of branches per plant, biomass yield, dry forage yield and harvest index were investigated. As a result of the research, statistically significant differences were seen between sowing dates at tested characteristics (P≤0.01). As a result of the research, statistically significant differences were seen between sowing dates at tested characteristics (P≤0.01). Plant height ranged from 81.8 cm to 109.4 cm, stem diameter from 9.0 mm to 12.6 mm, number of branches per plant from 10.3 to 12.7 number. The highest biomass yield was obtained from 1 April sowing date with 1751.40 kg da-1 whereas the lowest biomass yield was seen at June 15 sowing date with 1295.28 kg da-1. Dry matter yield values were between 415.8 (15 February) and 546.88 kg da-1 (1 April). Harvest index values were between 39.3% and 42.0%. Quinoa yield characteristics in generally increased from 15 February to 1 April sowing dates, but after 1 April sowing dates decreased. Higher values were obtained from April and May sowing dates. The most suitable planting date for quinoa plant in semi-arid climatic conditions was determined as 1 April and can be recommended in similar ecologies.

Identifying Forage Sorghum Ideotypes for Advanced Biorefineries

Forage sorghum is a promising feedstock for the production of biofuels and bioproducts because it is drought tolerant, high-yielding, and familiar to farmers across the world. However, sorghum spans a diverse range of phenotypes, and it is unclear which are most desirable as bioenergy feedstocks. This paper explores four forage sorghum types, including brown-midrib (bmr), non-bmr, photoperiod sensitive (PS), and photoperiod insensitive (non-PS), from the perspective of their impact on minimum bioethanol selling price (MESP) at an ionic liquid pretreatment-based biorefinery. Among these types, there are tradeoffs between biomass yield, lignin content, and starch and sugar contents. High biomass-yielding PS varieties have previously been considered preferable for bioenergy production, but, if most starch and sugars from the panicle are retained during storage, use of non-PS sorghum may result in lower-cost biofuels (MESP of $1.26/L-gasoline equivalent). If advances in lignin utilization increase its value such that it can be dried and sold for $0.50/kg, the MESP for each scenario is lowered and non-bmr varieties become the most attractive option (MESP of $1.08/L-gasoline equivalent). While bmr varieties have lower lignin content, their comparatively lower biomass yield results in higher transportation costs that negate its fuel-yield advantage.

Effects of Light Sources and Drying Methods on Plant Growth and Steviol Glycoside Content of Stevia rebaudiana Bertoni

Stevia (Stevia rebaudiana Bertoni) has received great attention with the rise in demand for low-sugar food and beverage additives, and natural alternative to cane sugar and artificial sweeteners. The leaves produce intensively sweet steviol glycosides (mainly stevioside and rebaudioside A). Stevia has been reported as a short-day plant with a critical daylength of 13 h. Daylength less than 13 h causes stevia to flower early, resulting in a low leaf biomass yield and percentage of sweetener content. The effects of night interruption treatment using six light sources for 60 min daily with the aim to lengthen vegetative phase, increase plant biomass and steviol glycoside content of stevia were investigated. Night interruption was shown to extend vegetative phase from 20 days (control) to 120 days; thus, allowing accumulation of plant biomass and steviol glycosides content. Leaf biomass and steviol glycosides of all light sources treated plants increased significantly as compared to control plants especially in week 6 and 8 after treatment initiated. Fluorescent and light-emitting diode (LED) were energy-efficient and effective as light source for night interruption. Fluorescent warm white showed the highest increase in total steviol glycosides content per plant by 190-270% most probably because it contained the highest red light at 614 nm as compared to other light sources. Stevioside content was not significantly affected by drying methods but rebaudioside A content was significantly reduced by 3.38% under oven drying at 70oC. The reduction indicated that thermal degradation of rebaudioside A has occurred at higher temperature.

Comparison of carrier particles in the gas–liquid-solid inverse fluidised bed bioreactor

ABSTRACT The performance and energy consumption of a gas–liquid-solid inverse fluidised bed bioreactor (GLS-IFBBR) using polyethylene (PE) particles with different surface coatings (zeolite, lava rock, activated carbon and multi-plastic) as media for synthetic wastewater treatment were investigated at loading rates of 1.64–3.38 kg COD/(m3·d) and 0.17–0.34 kg N/(m3·d) to determine the optimum carrier media. The results showed that PE coated with other inorganic materials could increase the nutrient removal efficiency at the same influent conditions. Compared with other media, PE coated with zeolite (PEZ) was the optimal carrier particles in this study as reflected by the highest COD and nitrogen removal, stable effluent, low biomass yield at different hydraulic retention times (HRT). In addition, the energy consumption of lavarock-coated PE (PEL) with a highest density was the lowest.

A novel microalgal biofilm reactor using walnut shell as substratum for microalgae biofilm cultivation and lipid accumulation

Microalgae are a potential candidate for biofuels, but the high cost and low biomass yield hinder the scale-up application of microalgae. In this study, a novel walnut shell based self-permeating biofilm reactor (WSPBR) was proposed for cultivation of Chlorella vulgaris (C. vulgaris) and Scenedesmus obliquus (S. obliquus). Major influencing factors such as walnut shell size, light intensity and CO2 concentration were studied in detail. The results showed that CO2 can enhance the storage of metabolic products in microalgal cells. Thermodynamics analysis indicated that C. vulgaris and S. obliquus were likely to adhere on the surface of walnut shells. S. obliquus and C. vulgaris biomass reached the maximum values of 97.43 and 70.49 g m−2, respectively, corresponding to the walnut shell size of 0.8–1.2 mm, light intensity of 150 μmol m−2 s−1 and CO2 concentration of 2%. The lipid contents of these microalgal cells were 34.32% and 28.94%, respectively. These results indicated that WSPBR was an efficient system for microalgae cultivation as feedstock for biofuels.

Short-Rotation Willows as a Wastewater Treatment Plant: Biomass Production and the Fate of Macronutrients and Metals

Evapotranspirative willow systems (EWS) are zero-discharge wastewater treatment plants that produce woody biomass and have no discharge to surface or groundwater bodies. The influence of wastewater on the growth of three clones of Salix alba (‘V 093’, ‘V 051’ and ‘V 160’) and the distribution of macronutrients and metals in a pilot EWS receiving primary treated municipal wastewater was studied under a sub-Mediterranean climate. The influent wastewater, shoot number, stem height, and biomass production at coppicing were monitored in two consecutive two-year rotations. Soil properties and the concentrations of macronutrients and metals in soil and woody biomass were analyzed after the first rotation. S. alba clones in EWS produced significantly more woody biomass compared to controls. ‘V 052’ produced the highest biomass yield in both rotations (38–59 t DM ha−1) and had the highest nitrogen and phosphorus uptake (48% and 45%) from wastewater. Nitrogen and phosphorus uptake into the harvestable woody biomass was significantly higher in all clones studied compared to other plant-based wastewater treatment plants, indicating the nutrient recovery potential of EWS. The indigenous white willow clone ‘V 160’ had the lowest biomass yield but absorbed more nutrients from wastewater compared to ‘V 093’. Wastewater composition and load were consistent with the nutrient requirements of the willows; however, an increase in salinity was observed after only two years of operation, which could affect EWS efficiency and nutrient recovery in the long term.

Towards Sustainable Bioinoculants: A Fermentation Strategy for High Cell Density Cultivation of Paraburkholderia sp. SOS3, a Plant Growth-Promoting Bacterium Isolated in Queensland, Australia

Paraburkholderia sp. SOS3 is a plant growth-promoting bacterium (PGPB) that displays pleiotropic effects and has the potential to be applied at a large scale across several agronomically important crops. The use of SOS3 is a suitable option to reduce the use of chemical fertilisers. While the benefits of SOS3 have been demonstrated in vitro, its potential applications at large scale are limited due to low biomass yield in current batch culture systems. Here, we developed a strategy for high-cell density cultivation of SOS3 in instrumented bioreactors, moving from low-biomass yield in a complex medium to high-biomass yield in a semi-defined medium. We achieved a 40-fold increase in biomass production, achieving cell densities of up to 11 g/L (OD600 = 40). This result was achieved when SOS3 was cultivated using a fed-batch strategy. Biomass productivity, initially 0.02 g/L/h in batch cultures, was improved 12-fold, reaching 0.24 g/L/h during fed-batch cultures. The biomass yield was also improved 10-fold from 0.07 to 0.71 gbiomass/gsolids. Analysis of the fermentation profile of SOS3 indicated minimal production of by-products and accumulation of polyhydroxybutyrate (PHB) during the exponential growth phase associated with nitrogen limitation in the medium. By implementing proteomics analysis in fed-batch cultures, we identified the expression of four metabolic pathways associated with growth-promoting effects, which may be used as a qualitative parameter to guarantee the efficacy of SOS3 when used as a bioinoculant. Ultimately, we confirmed that the high-cell density cultures maintained their plant growth-promoting capacity when tested in sorghum and maize under glasshouse conditions.

Economic viability of protein concentrate production from green biomass of intermediate crops: A pre-feasibility study

Green biomass is a major potential source of proteins for food and feed. This pre-feasibility study evaluates the use of green biomass of buckwheat, phacelia, hemp and oilseed radish grown as intermediate crops (IC) as a feedstock for production of protein concentrates to produce protein-rich food and feed products. We investigated the biomass yield, protein concentration and protein recovery potential of non-fertilized IC, nitrogen-fertilized IC and IC intercropped with legumes, harvested in late summer to autumn during 2017 and 2018 in southern Sweden. In addition, economic assessment of potential protein and fibre feed and food products were evaluated. The results showed that IC fertilized with 40 kg ha−1 N and intercropping with legumes contributed to a higher biomass dry matter (DM) yield of 4.9–5.8 t ha−1 as compared to between 2.2 and 3.1 t ha−1 for non-fertilized IC. Intercropping with legumes also resulted in higher protein yield of 154 g kg−1 vs. 103 g kg−1 for non-fertilized IC. Among IC, hemp, phacelia and oilseed radish showed up to ca. 25% higher DM yield and up to ca. 70% higher protein concentration as compared to buckwheat. Higher DM yield was obtained when IC were harvested in October and November than in August and September. Economic assessment was made on two feasible protein production pathways; (A) Green and white proteins and (B) total recoverable combined protein fraction (CPF). For all IC, cost per t DM was higher in August due to lower biomass yield as compared to other harvesting months. Nitrogen concentration was the main factor determining the size of revenues. Nitrogen concentration was 34% higher in 2018 compared to 2017 and therefore resulted in higher revenues in that year. Intercropping resulted in higher protein content and therefore contributed to lower breakeven prices of recovered green proteins for all IC. Breakeven price analyses showed that green protein and CPF were economically feasible to market as both bulk and premium products depending on lower (≤2 € kg−1) or higher (2–10 € kg−1) price ranges, respectively. The results demonstrate that use of IC biomass could be a feasible option to produce high value protein-rich products, which can contribute extra income from IC for farmers.

Rview of phytoremediation of soil contaminated by vanadium

Vanadium is a nontrivial multi-valent metallic element, which has been increasingly used in modern society. The widespread application of vanadium promotes the rapid and sound development of the economy and society, simultaneously brings out increasingly prominent environmental problems, e.g., soil vanadium pollution. Therefore, the remediation problem of vanadium-contaminated soil has been received growing attention. Phytoremediation has become a significant constituent in vanadium-contaminated soil remediation attributable to its veritable merits such as cleanness, esthetics, cost-effectiveness, convenience, and sustainability. Phytoremediation is mainly dependent on hyperaccumulator plants, even though the actuality that the vast majority of hyperaccumulator plants are characterized by low biomass yield and slow-growing. Consequently, the intensity in screening the undiscovered hyperaccumulators should be strengthened. Meanwhile, it is imperative to further explore the vanadium accumulation and translocation characteristics of some non-hyperaccumulative but tolerant plants with moderate biomass to remediate the soil contaminated with vanadium. Taken together, further comprehensive researches of tolerance mechanisms of remedial plants against vanadium are quite necessary to decontaminate soils contaminated by vanadium efficiently.

Evaluation of Improved Pigeon pea (&amp;lt;i&amp;gt;Cajanus cajan&amp;lt;/i&amp;gt;) Varieties at Adola, Guji Zone of Oromia

A study was conducted with the objective to identify adaptable, high biomass, good quality and seed yield of Pegeon pea cultivars at Adola sub-site of Bore Agricultural research center. Four pegeon pea cultivars Tsigas, Degagsa-75, Belabas-27 and 16555 were tested in RCBD with three replications. The analysis of variation revealed that significant (P<0.05) differ in days to 90% maturity were observed among cultivars. Among tested cultivars Belabas 27 was significantly earlier (162 days) to maturity, while late matured cultivar was Degagsa (203 days). Analysis of variance showed highly significant differences (P<0.01) were observed among cultivars for number of primary branches per plant. Higher branch number was recorded for Tsigas cultivar (21.6) whereas the lowest branch number was obtained from cultivar Degagsa-75 (9.75). The cultivars were significant (P<0.05) differ for pod length. The long pod was recorded from cultivar 16555 (5 cm) while the short pod length was recorded from cultivar Belabas -27 (3.14 cm). Cultivars were significant (P<0.05) varied for plant height. The long plant height was measured from cultivar Degagsa-75 (159.75 cm) followed by Tsigas (104.9 cm) whereas the short pant height was obtained from cultivar Belabas-27 (78.63 cm). Significant variations (P<0.05) in biomass yield between genotypes were observed (Table 2). Superior biomass yield was produced from Tsigas cultivar (2.17 ton/ha) followed by cultivar 16555 (1.27 ton/ha) while the low biomass yield was obtained from Degagsa-75 cultivar (0.97 ton/ha). In addition to the nutritional values were promising particularly the crude protein (CP) content in cultivar Tsigas. Based up on its adaptability, high biomass yield, seed yield and good CP of cultivar Tsigas and 16555 is recommended for further promotion in the midland of Guji zone and similar agro- ecologies.

Pseudomonas sp. Strain 273 Degrades Fluorinated Alkanes.

Fluorinated organic compounds have emerged as environmental constituents of concern. We demonstrate that the alkane degrader Pseudomonas sp. strain 273 utilizes terminally monofluorinated C7-C10 alkanes and 1,10-difluorodecane (DFD) as the sole carbon and energy sources in the presence of oxygen. Strain 273 degraded 1-fluorodecane (FD) (5.97 ± 0.22 mM, nominal) and DFD (5.62 ± 0.13 mM, nominal) within 7 days of incubation, and 92.7 ± 3.8 and 90.1 ± 1.9% of the theoretical maximum amounts of fluorine were recovered as inorganic fluoride, respectively. With n-decane, strain 273 attained (3.24 ± 0.14) × 107 cells per μmol of carbon consumed, while lower biomass yields of (2.48 ± 0.15) × 107 and (1.62 ± 0.23) × 107 cells were measured with FD or DFD as electron donors, respectively. The organism coupled decanol and decanoate oxidation to denitrification, but the utilization of (fluoro)alkanes was strictly oxygen-dependent, presumably because the initial attack on the terminal carbon requires oxygen. Fluorohexanoate was detected as an intermediate in cultures grown with FD or DFD, suggesting that the initial attack on the fluoroalkanes can occur on the terminal methyl or fluoromethyl groups. The findings indicate that specialized bacteria such as Pseudomonas sp. strain 273 can break carbon-fluorine bonds most likely with oxygenolytic enzyme systems and that terminally monofluorinated alkanes are susceptible to microbial degradation. The findings have implications for the fate of components associated with aqueous film-forming foam (AFFF) mixtures.

Chloride levels in biomass sorghum due to fertilization sources

The Brazilian energy matrix has 43.5% of renewable sources, a higher value than registered in the rest of the world (14%). The sugarcane bagasse used in sugarcane plants underlines the importance of this, which is the second-largest renewable source (17%) in this market segmentation, however, the installed systems could be better used in the offseason with alternative crops such as biomass sorghum (Sorghum bicolor L. Moench), which has a low production cost, short cycle, and high biomass yield. However, this alternative has shown a drawback: the presence of chloride in the biomass, which at the high temperature promotes corrosion of the boilers. Thus, the influence of different potassium fertilization and the harvest times of biomass sorghum on chloride levels in the final biomass were evaluated. The experiment was carried out in the state of São Paulo (Brazil), on the 2015/2016 harvest, using the Palo Alto® hybrid. A randomized block design with 4 replications was used, with 3 treatments for potassium sources (KCl, K2SO4, KNO3) in fertilization and 4 treatments related to harvest times (pre-flowering, flowering, milk grain, hard grain) in a factorial scheme. The results showed that the sources of fertilization do not affect productivity, however, when using KCl there are higher levels of chloride in the final biomass, therefore potassium sulfate or nitrate are better alternatives. The time with the lowest chloride level in the biomass is in the milk grain stage, positively correlating with the time of the highest dry matter production per hectare (38.35 Mg ha−1).

Energetics of Acidianus ambivalens growth in response to oxygen availability.

All life requires energy to drive metabolic reactions such as growth and cell maintenance; therefore, fluctuations in energy availability can alter microbial activity. There is a gap in our knowledge concerning how energy availability affects the growth of extreme chemolithoautotrophs. Toward this end, we investigated the growth of thermoacidophile Acidianus ambivalens during sulfur oxidation under aerobic to microaerophilic conditions. Calorimetry was used to measure enthalpy (ΔHinc ) of microbial activity, and chemical changes in growth media were measured to calculate Gibbs energy change (ΔGinc ) during incubation. In all experiments, Gibbs energy was primarily dissipated through the release of heat, which suggests enthalpy-driven growth. In microaerophilic conditions, growth was significantly more efficient in terms of biomass yield (defined as C-mol biomass per mole sulfur consumed) and resulted in lower ΔGinc and ΔHinc . ΔGinc in oxygen-limited (OL) and oxygen- and CO2 -limited (OCL) microaerophilic growth conditions resulted in averages of -1.44×103 kJ/C-mol and -7.56×102 kJ/C-mol, respectively, and average ΔHinc values of -1.11×105 kJ/C-mol and -4.43×104 kJ/C-mol, respectively. High-oxygen experiments resulted in lower biomass yield values, an increase in ΔGinc to -1.71×104 kJ/C-mol, and more exothermic ΔHinc values of -4.71×105 kJ/C-mol. The observed inefficiency in high-oxygen conditions may suggest larger maintenance energy demands due to oxidative stresses and a preference for growth in microaerophilic environments.

Strengthening flash light effect with a pond-tubular hybrid photobioreactor to improve microalgal biomass yield

Poor light utilization efficiency and large occupied area of traditional raceway pond photobioreactors result in low areal microalgal biomass yield in industrial applications. In this study, a pond-tubular hybrid photobioreactor (PTH-PBR) comprising raceway ponds and horizontal tubes was developed to strengthen flash light effect and improve areal microalgal biomass yield. The highest flash cycle frequency (0.63 Hz) of microalgae cells along flow pathway was obtained in the raceway pond of PTH-PBR when shaded area percentage was 20% and ratio of adjacent tube interval to tube diameter was 1, which enhanced microalgal biomass yield by 31.2% than traditional raceway pond. Meanwhile, intracellular chlorophyll content increased by 33.6% and PSII maximum quantum yield (Fv/Fm) increased by 8.1% due to decreased photoinhibition stress. The areal microalgal biomass yield of PTH-PBR was 54.7% higher than that of traditional raceway pond without horizontal tubes.

Model-driven analysis of mutant fitness experiments improves genome-scale metabolic models of Zymomonas mobilis ZM4.

Genome-scale metabolic models have been utilized extensively in the study and engineering of the organisms they describe. Here we present the analysis of a published dataset from pooled transposon mutant fitness experiments as an approach for improving the accuracy and gene-reaction associations of a metabolic model for Zymomonas mobilis ZM4, an industrially relevant ethanologenic organism with extremely high glycolytic flux and low biomass yield. Gene essentiality predictions made by the draft model were compared to data from individual pooled mutant experiments to identify areas of the model requiring deeper validation. Subsequent experiments showed that some of the discrepancies between the model and dataset were caused by polar effects, mis-mapped barcodes, or mutants carrying both wild-type and transposon disrupted gene copies—highlighting potential limitations inherent to data from individual mutants in these high-throughput datasets. Therefore, we analyzed correlations in fitness scores across all 492 experiments in the dataset in the context of functionally related metabolic reaction modules identified within the model via flux coupling analysis. These correlations were used to identify candidate genes for a reaction in histidine biosynthesis lacking an annotated gene and highlight metabolic modules with poorly correlated gene fitness scores. Additional genes for reactions involved in biotin, ubiquinone, and pyridoxine biosynthesis in Z. mobilis were identified and confirmed using mutant complementation experiments. These discovered genes, were incorporated into the final model, iZM4_478, which contains 747 metabolic and transport reactions (of which 612 have gene-protein-reaction associations), 478 genes, and 616 unique metabolites, making it one of the most complete models of Z. mobilis ZM4 to date. The methods of analysis that we applied here with the Z. mobilis transposon mutant dataset, could easily be utilized to improve future genome-scale metabolic reconstructions for organisms where these, or similar, high-throughput datasets are available.

Evaluation of pyrolysis chars derived from marine macroalgae silage as soil amendments.

Pyrolysis char residues from ensiled macroalgae were examined to determine their potential as growth promoters on germinating and transplanted seedlings. Macroalgae was harvested in May, July and August from beach collections, containing predominantly Laminaria digitata and Laminaria hyperborea; naturally seeded mussel lines dominated by Saccharina latissima; and lines seeded with cultivated L. digitata. Material was ensiled, pressed to pellets and underwent pyrolysis using a thermo‐catalytic reforming (TCR) process, with and without additional steam. The chars generated were then assessed through proximate and ultimate analysis. Seasonal changes had the prevalent impact on char composition, though using mixed beach‐harvested material gave a greater variability in elements than when using the offshore collections. Applying the char at 5% (v/v)/2% (w/w) into germination or seedling soils was universally negative for the plants, inhibiting or delaying all parameters assessed with no clear advantage in harvesting date, species or TCR processing methodology. In germinating lettuce seeds, soil containing the pyrolysis chars caused a longer germination time, poorer germination, fewer true leaves to be produced, a lower average plant health score and a lower final biomass yield. For transplanted ryegrass seedlings, there were lower plant survival rates, with surviving plants producing fewer leaves and tillers, lower biomass yields when cut and less regrowth after cutting. As water from the char‐contained plant pots inhibited the lettuce char control, one further observation was that run‐off water from the pyrolysis char released compounds which detrimentally affected cultivated plant growth. This study clearly shows that pyrolysed macroalgae char does not fit the standard assumption that chars can be used as soil amendments at 2% (w/w) addition levels. As the bioeconomy expands in the future, the end use of residues and wastes from bioprocessing will become a genuine global issue, requiring consideration and demonstration rather than hypothesized use.

Ammonia and Ammonium Exposure of Basil (Ocimum basilicum L.) Growing in an Organically Fertilized Peat Substrate and Strategies to Mitigate Related Harmful Impacts on Plant Growth.

Organic pot-based production of basil (Ocimum basilicum L.) often has lower biomass yield than conventional cultivation. Previous investigations indicate that this growth impairment is related to high ammonium (NH4 +) concentrations in the growing media released by the mineralization of organic nitrogen (N) fertilizers. However, as a result of this ammonification process substrate pH may also increase. Under neutral to alkaline conditions NH4 + is converted to ammonia (NH3), which is known to be phytotoxic even at low concentrations. Therefore, we investigated the impact of both ammonical N species on basil grown in a peat substrate. In total, three fertilization pot experiments were conducted in a greenhouse in order to compare the effect of different organic base dressings [250 and 750 mg N (L substrate)-1 mainly supplied by a liquid amino acid fertilizer (AAF)] and two initial substrate pH levels (5.5 and 6.5). In two treatments, 5% (v/v) mature compost was mixed into the peat 1 day and 12–days before the substrate was used for sowing, respectively. The aim of this procedure was to stimulate nitrification in this way to reduce ammonical N concentration. Ammonia concentration in the aerial plant surrounding environment was measured by using NH3 detector tubes in combination with an open-top chamber method. The results showed that the growth of basil (number of plants, fresh matter yield, plant height) was significantly inhibited in the second and third week of cultivation by rising NH3 and NH4 + exposure, as well as by a substrate pH ≥ 7.0. These adverse effects were reduced by lowering the organic base dressing rate and adjusting the initial substrate pH to 5.5. Furthermore, the addition of mature compost to peat in combination with a 12-day storage was proven to be effective for promoting nitrification in the organically fertilized substrate. As a result, plant growth was improved by both lower NH3 and NH4 + exposure as well as a faster supply of nitrate (NO3 -) as an additional N source. Using this approach, it was possible to feed organically fertilized basil right from the seedling stage with a NO3 --N/NH4 +-N-balanced and later on providing a predominant NO3 --N supply.