Crypthecodinium cohnii Growth and Omega Fatty Acid Production in Mediums Supplemented with Extract from Recycled Biomass

Crypthecodinium cohnii is a marine heterotrophic dinoflagellate that can accumulate high amounts of omega-3 polyunsaturated fatty acids (PUFAs), and thus has the potential to replace conventional PUFAs production with eco-friendlier technology. So far, C. cohnii cultivation has been mainly carried out with the use of yeast extract (YE) as a nitrogen source. In the present study, alternative carbon and nitrogen sources were studied: the extraction ethanol (EE), remaining after lipid extraction, as a carbon source, and dinoflagellate extract (DE) from recycled algae biomass C. cohnii as a source of carbon, nitrogen, and vitamins. In mediums with glucose and DE, the highest specific biomass growth rate reached a maximum of 1.012 h−1, while the biomass yield from substrate reached 0.601 g·g−1. EE as the carbon source, in comparison to pure ethanol, showed good results in terms of stimulating the biomass growth rate (an 18.5% increase in specific biomass growth rate was observed). DE supplement to the EE-based mediums promoted both the biomass growth (the specific growth rate reached 0.701 h−1) and yield from the substrate (0.234 g·g−1). The FTIR spectroscopy data showed that mediums supplemented with EE or DE promoted the accumulation of PUFAs/docosahexaenoic acid (DHA), when compared to mediums containing glucose and commercial YE.

Potential Use of Plant Biomass from Treatment Wetland Systems for Producing Biofuels through a Biocrude Green-Biorefining Platform

The potential of using the biomass of four wetland plant species (Iris pseudacorus, Juncus effusus, Phragmites australis and Typha latifolia) grown in treatment wetland systems and under natural conditions were tested to produce high-value materials using hydro-thermal liquefaction (HTL). The results show that the wetland plants biomass is suitable for biocrude and biochar production regardless of the origin. The hydrothermal liquefaction products’ (biocrude, biochar, aqueous and gaseous phase) yields vary according with the specific biomass composition of the species. Furthermore, the results show that the biomass composition can be affected by the growing condition (treatment wetland or natural unpolluted conditions) of the plants. None of the single components seems to have a determinant effect on the biocrude yields, which reached around 30% for all the analyzed plants. On the contrary, the biochar yields seem to be affected by the composition of the biomass, obtaining different yields for the different plant species, with biochar yields values from around 12% to 22%, being that Phragmites australis is the one with the highest average yield. The obtained aqueous phase from the different plant species produces homogeneous compounds for each plant species and each growing environment. The study shows that biomass from treatment wetlands is suitable for biocrude production. The environmental value of this biomass lies on the fact that it is considered a residual product with no aggregated value. The treatment wetland biomass is a potential sustainable source for biofuel production since these plants do not need extra land or nutrients for growing, and the biomass does not compete with other uses, offering new sources for enhancing the bioeconomy concepts.

Epiphyton in Agricultural Streams: Structural Control and Comparison to Epilithon

Stream biofilms play an important role in the structure, functioning, and integrity of agricultural streams. In many lowland streams, macrophyte vegetation is abundant and functions as an important substrate for biofilm (epiphyton) in addition to the gravel and stone substrate for epilithon on the stream bed. We expect that reach-scale habitat conditions in streams (e.g., nutrient availability, hydraulic conditions) affect the epiphyton and epilithon biomass and composition, and that this effect will be substrate-specific (macrophytes and stones). The objectives of our study were (i) to describe concurrent changes in epiphyton and epilithon biomass and composition over a year in agricultural streams, and (ii) to determine the substrate specific reach-scale habitat drivers for the epiphyton and epilithon structure. We monitored epiphyton and epilithon biofilm biomass and composition at three-week intervals and reach-scale environmental conditions daily during a year for two agricultural steams. The results showed that epiphyton and epilithon communities differed in biomass, having high substrate specific biomass in epilithon compared to epiphyton. Epiphyton was mainly composed of diatom and green algae, while cyanobacteria were more important in epilithon, and the diatom species composition varied between the two biofilm types. Epiphyton structural properties were less influenced by reach-scale hydrology and nutrient availability compared to epilithon. The overall explanatory power of the measured environmental variables was low, probably due to micro-scale habitat effects and interactive processes within stream biofilms. Knowledge of biofilm control in agricultural streams is important in order to improve management strategies, and future studies should improve the understanding of micro-scale habitat conditions, interactive relationships within biofilms and between the biofilm and the substrates.

Quantification of macromolecular biomass composition for constraint-based metabolic modeling

Genome-scale metabolic models (GEMs) are mathematical representations of metabolism that allow for in silico simulation of metabolic phenotypes and capabilities. A prerequisite for these predictions is an accurate representation of the biomolecular composition of the cell necessary for replication and growth, implemented in GEMs as the so-called biomass objective function (BOF). The BOF contains the metabolic precursors required for synthesis of the cellular macro- and micromolecular constituents (e.g. protein, RNA, DNA), and its composition is highly dependent on the particular organism, strain, and growth condition. Despite its critical role, the BOF is rarely constructed using specific measurements of the modeled organism, drawing the validity of this approach into question. Thus, there is a need to establish robust and reliable protocols for experimental condition-specific biomass determination. Here, we address this challenge by presenting a general pipeline for biomass quantification, evaluating its performance on Escherichia coli K-12 MG1655 sampled during balanced exponential growth under controlled conditions in a batch-fermentor set-up. We significantly improve both the coverage and molecular resolution compared to previously published workflows, quantifying 91.6% of the biomass. Our measurements display great correspondence with previously reported measurements, and we were also able to detect subtle characteristics specific to the particular E. coli strain. Using the modified E. coli GEM iML1515a, we compare the feasible flux ranges of our experimentally determined BOF with the original BOF, finding that the changes in BOF coefficients considerably affect the attainable fluxes at the genome-scale.

Correlations between maximum reductive dechlorination rates and specific biomass parameters in Dehalococcoides mccartyi consortia enriched on chloroethenes PCE, TCE, and cis-1,2-DCE

One of the challenges to implementing the modeling of the biological reductive dechlorination (RD) process is the evaluation of biological parameters that represent the abundance/activity levels of the microorganisms involved in the biodegradation of chloroethenes. Here we report a combined analysis of kinetic and specific biomass parameters conducted on three dechlorinating consortia enriched on PCE, TCE, and cis-1,2-DCE. In these consortia, Dehalococcoides mccartyi (Dhc) represented ≥ 70% of the bacterial population identified via 16S rRNA gene amplicon sequencing. Quantitative biomolecular methods were used to generate specific biomass parameters targeting either the Dhc population (16S rRNA genes or cells) or specific genes encoding RD process-involved reductive dehalogenases. The correlation factor between the abundance of active Dhc cells or tceA gene copies and maximum RD rates allowed to predict an increment of 7E+09 of active Dhc cells or 5E+09 tceA gene copies L−1 under controlled conditions. Diversely, the utilization of gene transcripts as biomass parameters for RD modeling did not provide reliable correlations with kinetic performances. This study provides valuable insights for further modeling of the RD process through the utilization of specific biomass parameters.

The Rabbitfish Siganus virgatus as Key Macroalgae Browser in Coral Reefs of the Gulf of Thailand

Coral reef resilience is greatly influenced by herbivory. There is a need to identify key fish species fulfilling this critical function in biogeographically distinct regions. This experimental in situ study investigated fish herbivory in coral reefs of the lower Gulf of Thailand characterized by a considerably low herbivorous fish biomass and diversity, but high live coral and low macroalgal cover. This provided an intriguing situation for macroalgal browsing research. Visual census techniques assessed the abundance of local herbivorous fish species, and filmed single-choice assays using the macroalga Turbinaria evaluated mass-standardized bites (ms-bites) and biomass removal. Multiple-choice assays offering four locally abundant macroalgae identified specific biomass removal and ms-bites to uncover selection and avoidance patterns of observed fish species. The rabbitfish Siganusvirgatus constituted only 39% of herbivore biomass but accounted for 90% of ms-bites. In multiple-choice assays, fishes took most (61%) bites on Sargassum, followed by Padina (28%) and Turbinaria (11%), while Lobophora was avoided. S. virgatus exhibited the most generalized browsing pattern of all species observed. Coinciding with recent studies, our findings suggest that S. virgatus plays a key functional role in reefs characterized by low diversity of herbivores and low functional redundancy.

Performance and Kinetic Evaluation of Palm Oil Mill Effluent (POME) Digestion in a Continuous High Rate Up-Flow Anaerobic Sludge Blanket (UASB) Bioreactor

In this study, we operated a 10 litre upflow anaerobic sludge blanket (UASB) reactor continuosly at mesophilic temperature (38 °C). UASB reactor performance was evaluated based on the impact of the hydraulic retention time (HRT) ranged between 1 and 5 days and influent COD concentration in the range of 4540 mgL-1 and 20,820 mgL-1. The pH of the UASB was maintained in the range of 6.5 to 7.2 by adding buffering solution containing of 5 gL-1 of calcium oxide (CaO) derived from waste cockle shells. A simplified Monod’s model was employed to describe kinetics of anaerobic digestion of POME by using UASB reactor at organic loading rates (OLR) in the range between 1.17 g.CODL-1d-1 and 17.22 g.CODL-1d-1. A high COD degradation rate of 93.26 % was recorded at OLR of 3.92 g.COD L-1d-1 and HRT of 4 days. The UASB reactor generated the maximum biogas production at 34.95 L/d when operated at HRT 1 day and OLR 7.70 g.CODL-1. The proposed kinetic equations are applicable to describe anaerobic treatment of palm oil mill effluent with the UASB reactor. Biokinetic coefficients evaluated were, the growth yield (YG), 3.906 g VSS/g CODremoved.d-1; the specific biomass decay (b), 0.233 d-1; the specific biomass growth rate (μmax), 1.861 d-1; and the saturation constant (Ks), 3.459 g-CODL-1.

Plant morphology, vegetative biomass composition and energy content of three different Silybum marianum accessions

Silybum marianum (L.) Gaertn. (milk thistle) is plant species that has been utilized principally for medicinal purposes for more than 2000 years. Recently it was proposed for biomass production in marginal environments, but vegetative biomass compositional analyses had not been available so far. The study of plant morphology and biomass composition was conducted on three different S. marianum accessions grown under open field conditions. The results indicate that plant morphological traits show major differences between accessions: this suggests that the available natural variability can be further utilized in order to develop improved S. marianum cultivars. Biomass compositional analysis shows that extractives, ash, lignin and cellulose content are comparable to other herbaceous bioenergy crops and that these traits display only limited variability in the studied accessions. Hemicellulose fraction is composed only by xylans and its content appears averagely lower in comparison to other herbaceous biomasses. Interestingly, in S. marianum biomass total nitrogen content is lower if compared to other herbaceous species. The possible involvement of this specific biomass trait in S. marianum nitrogen utilization efficiency has to be further investigated.