Biomass production and nitrogen and phosphorus removal by the green alga Neochloris oleoabundans in simulated wastewater and secondary municipal wastewater effluent

Biomass productivity of 350 mg DCW L⁻¹ day⁻¹ with a final biomass concentration of 3.15 g DCW L⁻¹ was obtained with Neochloris oleoabundans grown in artificial wastewater at sodium nitrate and phosphate concentrations of 140 and 47 mg L⁻¹, respectively, with undetectable levels of residual N and P in effluents. In secondary municipal wastewater effluents enriched with 70 mg N L⁻¹, the alga achieved a final biomass concentration of 2.1 g DCW L⁻¹ and a biomass productivity of 233.3 mg DCW L⁻¹ day⁻¹. While N removal was very sensitive to N:P ratio, P removal was independent of N:P ratio in the tested range. These results indicate that N. oleoabundans could potentially be employed for combined biofuel production and wastewater treatment.     

Modeling of biomass production by Spirulinaplatensis as function of phosphate concentrations and pH regimes

Batch cultivations were performed to evaluate the influence of phosphate concentrations (0.25, 0.5, 0.75, and 1.0 g L⁻¹) for pH regimes (9.5, 10.0, and 10.5) on the biomass production by Spirulina platensis. The best condition for cell growth (3.099 g L⁻¹) was found at 0.5 g L⁻¹ phosphate and pH value of 10.0. Cultivation time, phosphate, and pH caused to increase significantly (p < 0.01) in biomass production by S. platensis. Lag time was observed up to 4 h. After then, biomass production increased sharply (p < 0.01) from 0.020 g L⁻¹ to 2.063, 2.213, 1.532, and 0.797 g L⁻¹ at 0.25, 0.5, 0.75, and 1.0 g L⁻¹ phosphate values, respectively. Modified Gompertz model could be regarded as sufficient to describe the biomass production by S. platensis with high determination coefficients and low sum of square value indicated that. Biological parameters for biomass production were successfully predicted by modified Gompertz model.     

Overyielding and the role of complementary use of nitrogen in wetland plant communities

Biodiversity and ecosystem functioning experiments have demonstrated that plant biomass of species grown in mixtures is often greater than plant biomass of monocultures (i.e., mixtures over yield). While we understand that plant species utilize resources differently, how a combination of species increases resource use and productivity is not well known, especially in wetland ecosystems. Here, we used a mesocosm experiment to explore diversity effects on plant biomass production and to examine the role of N partitioning as a mechanism for overyielding in wetland ecosystems. Plant functional groups (FGs) represented the unit of diversity, and we included five levels of diversity (0-4 FGs). To test for N partitioning, we used a stable isotope technique to determine niche breadth and proportion similarity of inorganic N use (NO₃⁻ and NH₄⁺) for individual FGs as well as mixtures containing 3 and 4 FGs. We found that total plant biomass increased in the first season from an average of 290 ± 60 SE g ash-free dry mass (AFDM) m⁻² at the 1 FG level to 490 ± 70 g AFDM m⁻² at the 4 FG level and in the second season from an average of 560 ± 80 g AFDM m⁻² at the 1 FG level to 1000 ± 90 g AFDM m⁻² at the 4 FG level indicating overyielding. Plant species comprising the majority of mesocosm biomass demonstrated preferential uptake of ¹⁵NO₃⁻, while species with relatively less biomass (e.g., Acorus calamus and Carex crinita) preferred ¹⁵NH₄⁺. Concentrations of ¹⁵N in biomass increased with FG richness, but only in the ¹⁵NO₃⁻ treatment. Niche breadth did not vary among levels of FG richness. We observed a greater niche overlap with an increase of FGs, with species taking up greater proportion of ¹⁵NO₃⁻ than ¹⁵NH₄⁺. Our results indicate that plant overyielding in wetland mesocosms is not the result of niche partitioning of N chemical forms, but is associated with greater uptake of NO₃.     

Cultivation of microalgae for oil production with a cultivation strategy of urea limitation

The microalgae, Chlorella sp., were cultivated in various culture modes to assess biomass and lipid productivity in this study. In the batch mode, the biomass concentrations and lipid content of Chlorella sp. cultivated in a medium containing 0.025–0.200 g L⁻¹ urea were 0.464–2.027 g L⁻¹ and 0.661–0.326 g g⁻¹, respectively. The maximum lipid productivity of 0.124 g d⁻¹ L⁻¹ occurred in a medium containing 0.100 g L⁻¹ urea. In the fed-batch cultivation, the highest lipid content was obtained by feeding 0.025 g L⁻¹ of urea during the stationary phase, but the lipid productivity was not significantly increased. However, a semi-continuous process was carried out by harvesting the culture and renewing urea at 0.025 g L⁻¹ each time when the cultivation achieved the early stationary phase. The maximum lipid productivity of 0.139 g d⁻¹ L⁻¹ in the semi-continuous culture was highest in comparison with those in the batch and fed-batch cultivations.     

Development of chemically defined media supporting high cell density growth of Ketogulonicigenium vulgare and Bacillus megaterium

The immediate precursor of L-ascorbic acid, or vitamin C, is 2-keto-l-gulonic acid (2-KLG). This is commonly produced commercially by Ketogulonicigenium vulgare and Bacillus megaterium, using corn steep liquor powder (CSLP) as an organic nitrogen source. In this study, the effects of the individual CSLP components (amino acids, vitamins, and metal elements) on 2-KLG production were evaluated, with the aim of developing a complete, chemically defined medium for 2-KLG production. Forty components of CSLP were analyzed, and key components were correlated to biomass, 2-KLG productivity, and consumption rate of L-sorbose. Glycine had the greatest effect, followed by serine, biotin, proline, nicotinic acid, and threonine. The combination of 0.28 g L⁻¹ serine, 0.36 g L⁻¹glycine, 0.18 g L⁻¹ threonine, 0.28 g L⁻¹proline, 0.19 g L⁻¹nicotinic acid, and 0.62 mg L⁻¹biotin in a chemically defined medium produced the highest maximum biomass concentration (4.2 × 10⁹ cfu mL⁻¹), 2-KLG concentration (58 g L⁻¹), and yield (0.76 g g⁻¹) after culturing for 28 h.     

In silico optimization and low structured kinetic model of poly[(R)-3-hydroxybutyrate] synthesis by Cupriavidus necator DSM 545 by fed-batch cultivation on glycerol

Glycerol was utilized by Cupriavidus necator DSM 545 for production of poly-3-hydroxybutyrate (PHB) in fed-batch fermentation. Maximal specific growth rates (0.12 and 0.3 h⁻¹) and maximal specific non-growth PHB production rate (0.16 g g⁻¹ h⁻¹) were determined from two experiments (inocula from exponential and stationary phase). Saturation constants for nitrogen (0.107 and 0.016 g L⁻¹), glycerol (0.05 g L⁻¹), non-growth related PHB synthesis (0.011 g L⁻¹) and nitrogen/PHB related inhibition constant (0.405 g L⁻¹), were estimated. Five relations for specific growth rate were tested using mathematical models. In silico performed optimization procedures (varied glycerol/nitrogen ratio and feeding) has resulted in a PHB content of 70.9%, shorter cultivation time (23 h) and better PHB yield (0.347 g g⁻¹). Initial concentration of biomass 16.8 g L⁻¹ and glycerol concentration in broth between 3 and 5 g L⁻¹ were decisive factors for increasing of productivity.     

Optimization of growth media for obtaining high-cell density cultures of halophilic archaea (family Halobacteriaceae) by response surface methodology

Optimization of media components for the growth and biomass production of Halobacterium salinarum VKMM 013 was carried out using response surface methodology. A second order quadratic model was estimated and media components were determined based on quadratic regression equation generated by model. These were 6.35 g L⁻¹ of KCl, 9.70 g L⁻¹ of MgSO₄, 13.38 g L⁻¹ of gelatin and 12.00 g L⁻¹ of soluble starch in nutrient broth supplemented with artificial seawater with 20% (w/v) of NaCl. In these optimal conditions, the obtained cell concentration of 0.746 g L⁻¹ dry weight was in agreement with the predicted cell concentration. The optimized media significantly shortened the time required for cell culture to reach the stationary phase while providing a nearly 2.4-fold increase in biomass production. Furthermore, in cell cultures of three other halophilic archaea the use of optimized media enhanced growth rate and provided high-cell density.     

Effects of biomass weight and light intensity on the performance of photosynthetic microbial fuel cells with Spirulina platensis

Microalgae Spirulina platensis were attached to the anode of a membrane-free and mediator-free microbial fuel cell (MFC) to produce electricity through the consumption of biochemical compounds inside the microalgae. An increase in open circuit voltage (OCV) was observed with decreasing light intensity and optimal biomass area density. The highest OCV observation for the MFC was 0.39 V in the dark with a biomass area density on the anode surface of 1.2 g cm⁻². Additionally, it was observed that the MFC with 0.75 g cm⁻² of biomass area density produced 1.64 mW m⁻² of electrical power in the dark, which is superior to the 0.132 mW m⁻² produced in the light. Which also means the MFC can be applied to generate electrical power under both day and night conditions.     

Atmospheric phenanthrene transfer and effects on two grassland species and their root symbionts: A microcosm study

The objective of this work was to determine the transfer of phenanthrene (PHE) from air to grassland plants and soil compartments and its effects on the plant growth and symbiotic root microorganisms (arbuscular mycorrhizal fungi and Rhizobium nodules). The experimental procedure exposed Trifolium pratense L. or Lolium perenne L. to atmospheric PHE pollution (150 μg m⁻³) over the course of one month. PHE was transferred from the air to the leaves and to the soil surfaces. In leaves, PHE was mostly absorbed in the inner leaf tissues, representing 92% and 73% of the total PHE amount quantified in leaves, respectively for clover and ryegrass. In soils, most of PHE contamination was recovered in the top layer (0-1 cm) and did not readily diffuse into the deep layer (1-10 cm). The highest PHE concentration recovered in deep roots (1.8 and 4.5 μg g⁻¹ dry weight (DW), respectively for clover and ryegrass) related to the lowest PHE concentration recovered in its associated soil suggested a PHE translocation from shoots to roots within the two plant species. The large PHE amount quantified in clover shoots (124 μg g⁻¹ DW) induced a significant diminution by 30% of the shoot biomass whereas root biomass remained stable. Efficient mycorrhizal symbiosis was maintained during exposure whereas the Rhizobium nodule symbiosis was altered in the surface of soil. By contrast, neither biomass accumulation nor symbiotic association was affected in ryegrass, probably due to a lower sensitivity of this species to PHE exposure. Perspectives of carbon allocation and nitrogen nutrition perturbations are suggested in clovers.     

Response of native Egeria najas Planch. and invasive Hydrilla verticillata (L.f.) Royle to altered hydroecological regime in a subtropical river

Egeria najas Planch. is the dominant native submersed macrophyte of the Upper Paraná River in Brazil, while Hydrilla verticillata (L.f.) Royle has recently invaded this area. From January 2006 to December 2007, comprising two annual flood cycles, we conducted monthly surveys at two river stations and two lakes connected to the river within this stretch of the Paraná River, aiming to understand how the hydrological regime influences the distribution and abundance of these native and invasive Hydrocharitaceae species. Hydrilla did not develop in the lakes, possibly due to the elevated proportion of organic matter in the sediment (∼10% DW). However, the exotic species dominated the river sites apparently suppressing E. najas. In the lakes E. najas reached a maximum biomass of 628 ± 82 g DW m⁻² but did not surpass 333 ± 83 g DW m⁻² in the river, where H. verticillata peaked at 1415 ± 255 g DW m⁻². Macrophyte biomass development was greatest during low-water periods, with transparent water and high temperatures. Floods probably affected submersed macrophytes (especially in 2007, when an extreme flood caused by an El Niño Southern Oscillation (ENSO) event occurred) via sediment movement and plant scouring (uprooting) effects, coupled with reduced water transparency. Macrophyte recovery started soon after the (less intense) 2006 flood but was delayed in 2007. In the river recovery started five months after the major flood, but in the lakes no significant plant regeneration was found even nine months after the disturbance. E. najas and H. verticillata started regeneration practically at the same time but H. verticillata had much higher rates of biomass increase.