Phycoremediation of pollutants from secondary treated coke-oven wastewater using poultry litter as nutrient source: a cost-effective polishing technique

The present article focuses on the phycoremediation of pollutants from secondary treated coke-oven effluent through a green and economical route. A microalgal sample was collected and identified as a consortium of Chlorella sp. and Synechococcus sp. The culture cost was reduced by using poultry litter extract as supplementary material to BG-11 medium. Since major pollutants as present in real secondary treated coke-oven wastewater are phenol, ammoniacal-N (NH4+) and cyanide, several matrices were designed with these three major pollutants by varying their initial concentrations such as phenol (2–10 mgL−1), cyanide (0.3–1 mgL−1) and NH4+ (100–200 mgL−1), termed as simulated secondary treated coke-oven wastewater. Maximum removal was observed with individual solutions of phenol (4 mgL−1), cyanide (0.6 mgL−1), and NH4+ (175 mgL−1) while maximum removal in simulated secondary treated coke-oven wastewater was observed at higher concentrations of phenol (8 mgL−1) and cyanide (0.8 mgL−1) and the same concentration of NH4+ (175 mgL−1). Consortium was found effective to meet statutory limits of pollutants. Kinetic model was developed for predicting growth of consortium and observed that the poultry litter extract enriched BG-11 medium showed higher values of maximum specific growth rate (0.56 day−1) and carrying capacity (1,330 mgL−1) than that in BG-11 medium only.

The Relationship Between the Biokinetic Parameters of an Aerobic Granular Sludge System and the Applied Operating Conditions

Biokinetic parameters help to describe the rate of substrate utilization and biomass production or growth by microbial action, which is important to the design process and performance optimization of wastewater treatment. Although studies of the biokinetic parameters of aerobic granular sludge (AGS) systems have been increasing lately, the significance for each value in terms of maximum specific growth rate (μmax), substrate concentration at one-half of the maximum specific growth rate (KS), and cell yield (Y) in relation to the applied operating conditions are rarely discussed. Therefore, this study investigates the relationship and significance between the above-stated biokinetic parameters with organic loading rate (OLR) and reactor height/diameter (H/D) ratio from five different batches of AGS treated sewage, using the independent t-test. The biokinetic parameters are summarized as biomass production (Y and μmax ) and relied upon the relative increase in the OLR and reactor H/D ratios. Additionally, aerobic granules developed in reactors with a high H/D ratio have a shorter setup time and are more active in contrast with low H/D ratio reactors.

A predictive growth model for Yarrowia lipolytica ATCC 9773 in wastewater

This study focuses on the development of a secondary model for Yarrowia lipolytica in a sewage treatment process. The raw data of Y. lipolytica growth were adjusted to the Buchanan model in order to obtain growth parameters such as initial count cells (Y0), maximum specific growth rate (μmax), latency phase (λ) and maximum cell population (Ymax). The µ values obtained at different pH levels (5.0 to 8.0) were used to build the secondary model based on a linear equation. The results showed a significant effect of pH on µmax values. The validation process of the developed models displays accuracy (Af) and bias factor (Bf) values close to one, while the values of root mean square error (RMSE) were low, confirming that such models can predict the growth of Y. lipolytica in dairy wastewater. This can be interesting to optimize sewage treatments that involve this kind of microorganism. Moreover, the dairy wastewater was a good substrate to support the Yarrowia lipolytica's growth and could be used to produce enzymes.

Quantifying relative virulence: when μ max fails and AUC alone just is not enough

A challenge in virology is quantifying relative virulence (V R) between two (or more) viruses that exhibit different replication dynamics in a given susceptible host. Host growth curve analysis is often used to mathematically characterize virus–host interactions and to quantify the magnitude of detriment to host due to viral infection. Quantifying V R using canonical parameters, like maximum specific growth rate (μ max), can fail to provide reliable information regarding virulence. Although area-under-the-curve (AUC) calculations are more robust, they are sensitive to limit selection. Using empirical data from Sulfolobus Spindle-shaped Virus (SSV) infections, we introduce a novel, simple metric that has proven to be more robust than existing methods for assessing V R. This metric (I SC) accurately aligns biological phenomena with quantified metrics to determine V R. It also addresses a gap in virology by permitting comparisons between different non-lytic virus infections or non-lytic versus lytic virus infections on a given host in single-virus/single-host infections.

Biosurfactant Production and Growth Kinetics Studies of the Waste Canola Oil-Degrading Bacterium Rhodococcus erythropolis AQ5-07 from Antarctica

With the progressive increase in human activities in the Antarctic region, the possibility of domestic oil spillage also increases. Developing means for the removal of oils, such as canola oil, from the environment and waste “grey” water using biological approaches is therefore desirable, since the thermal process of oil degradation is expensive and ineffective. Thus, in this study an indigenous cold-adapted Antarctic soil bacterium, Rhodococcus erythropolis strain AQ5-07, was screened for biosurfactant production ability using the multiple approaches of blood haemolysis, surface tension, emulsification index, oil spreading, drop collapse and “MATH” assay for cellular hydrophobicity. The growth kinetics of the bacterium containing different canola oil concentration was studied. The strain showed β-haemolysis on blood agar with a high emulsification index and low surface tension value of 91.5% and 25.14 mN/m, respectively. Of the models tested, the Haldane model provided the best description of the growth kinetics, although several models were similar in performance. Parameters obtained from the modelling were the maximum specific growth rate (qmax), concentration of substrate at the half maximum specific growth rate, Ks% (v/v) and the inhibition constant Ki% (v/v), with values of 0.142 h−1, 7.743% (v/v) and 0.399% (v/v), respectively. These biological coefficients are useful in predicting growth conditions for batch studies, and also relevant to “in field” bioremediation strategies where the concentration of oil might need to be diluted to non-toxic levels prior to remediation. Biosurfactants can also have application in enhanced oil recovery (EOR) under different environmental conditions.

Valorisation of agroindustrial residues acid hydrolyzates as carbon sources for ethanol production by native yeast strains with different fermentative capabilities//Valorización de hidrolizados ácidos de residuos agroindustriales como fuente de carbono para la producción de etanol por levaduras nativas con capacidades fermentativas diferentes

A profitable, second-generation (2G) bioethanol production process requires the use of the maximum amountof sugars present in the lignocellulosic biomass; among them are those obtained from hemicellulose hydrolysis. An alternative is the search and kinetic characterization of yeasts capable of fermenting xylose to ethanol. In this study, 161 yeasts were isolated from agroindustrial residues, and selected according to best growth in glucose and xylose. Five strains belonging to the genera Candida (C. intermedia and C. parapsilosis), and Wickerhamomyces (W. anomalus) were molecularly identified. The kinetic parameters indicate that C. intermedia CBE002 had the best biomass yield in glucose and xylose (0.21 and 0.35 g/g of substrate), maximum specific growth rate (0.15 and 0.12 h-1) and metabolized both sugars simultaneously, desirable characteristics and rarely found together in other yeasts. Bioethanol production was made possible by C. intermedia (CBE002) from acid hydrolysates of corn stover and mango residues, with yields of 0.31 and 0.26 g/g of substrate, respectively. From the results obtained, this yeast is an attractive candidate to be used in bioethanol 2G production, and to take advantage of the large amount of agroindustrial residues available.RESUMENUn proceso de producción de bioetanol de segunda generación (2G) rentable, requiere el uso del máximo número de azúcares presentes en la biomasa lignocelulósica, como son los obtenidos por hidrólisis de hemicelulosa; para obtenerlo, una alternativa es encontrar levaduras capaces de fermentar eficientemente xilosa a etanol. En el presente trabajo se realizó el aislamiento de 161 levaduras a partir de residuos agroindustriales, se evaluó su capacidad de crecimiento en glucosa y xilosa. Se seleccionaron e identificaron molecularmente cinco de estas cepas pertenecientes a los géneros Candida (C. intermedia, C. parapsilosis) y Wickerhamomyces (W. anomalus). Los parámetros cinéticos demostraron que C. intermedia CBE002 obtuvo el mejor rendimiento de biomasa en glucosa y xilosa (0.21 y 0.35 g/g), la máxima velocidad específica de crecimiento (0.15 y 0.12 h-1) y fue capaz de metabolizar ambos azúcares simultáneamente, característica deseable y poco encontrada en otras levaduras. Fue posible la producción de bioetanol por C. intermedia CBE002 a partir de hidrolizados ácidos de rastrojo de maíz y residuos de mango, con rendimientos de 0.31 y 0.26 g/g de sustrato, respectivamente. Por lo anterior, esta levadura es atractiva para ser empleada en la producción de bioetanol 2G y aprovechar la gran cantidad de residuos agroindustriales disponibles.

Anaplerotic reactions active during growth of Saccharomyces cerevisiae on glycerol

ABSTRACT Anaplerotic reactions replenish TCA cycle intermediates during growth. In Saccharomyces cerevisiae, pyruvate carboxylase and the glyoxylate cycle have been experimentally identified to be the main anaplerotic routes during growth on glucose (C6) and ethanol (C2), respectively. The current study investigates the importance of the two isoenzymes of pyruvate carboxylase (PYC1 and PYC2) and one of the key enzymes of the glyoxylate cycle (ICL1) for growth on glycerol (C3) as a sole carbon source. As the wild-type strains of the CEN.PK family are unable to grow in pure synthetic glycerol medium, a reverse engineered derivative showing a maximum specific growth rate of 0.14 h−1 was used as the reference strain. While the deletion of PYC1 reduced the maximum specific growth rate by about 38%, the deletion of PYC2 had no significant impact, neither in the reference strain nor in the pyc1Δ mutant. The deletion of ICL1 only marginally reduced growth of the reference strain but further decreased the growth rate of the pyc1 deletion strain by 20%. Interestingly, the triple deletion (pyc1Δ pyc2Δ icl1Δ) did not show any growth. Therefore, both the pyruvate carboxylase and the glyoxylate cycle are involved in anaplerosis during growth on glycerol.

Elucidating the competition between heterotrophic denitrification and DNRA using the resource-ratio theory

Denitrification and dissimilatory nitrate reduction to ammonium (DNRA) are two microbial processes competing for nitrate and organic carbon (COD). Their competition has great implications for nitrogen loss, conservation, and greenhouse gas emissions. Nevertheless, a comprehensive and mechanistic understanding of the governing factors for this competition is still lacking. We applied the resource-ratio theory and verified it with competition experiments of denitrification and DNRA reported in the literature. Based on this theory, we revealed how COD/N ratio, influent resource concentrations, dilution rate, and stoichiometric and kinetic parameters individually and collectively define the boundaries for different competition outcomes in continuous cultures. The influent COD/N ratio alone did not drive competition outcome as the boundary COD/N ratio for different competition outcomes changed significantly with influent resource concentrations. The stoichiometry of the two processes was determinative for the boundaries, whereas the affinity for the resources (Ks), maximum specific growth rate (μmax) of the two species and the dilution rate had significant impacts as well but mainly at low influent resource concentrations (e.g., <100 μM nitrate). The proposed approach allows for a more comprehensive understanding of the parameters controlling microbial selection and explains apparently conflicting experimental results. The results from this model also provide testable hypotheses and tools for understanding and managing the fate of nitrate in ecosystems and for other species that compete for two resources.

Characterization of different microalgae cultivated in open ponds

Microalga is one of the main sources of biomasses for the production of biofuels in the 21st century. Many labs and industries around the world are seeking for more productive strains and better cultivation models. The aim of this work was to evaluate the growth and kinetic parameters of six microalgae, and the moisture and lipid contents and fatty acids profiles of the biomasses harvested at the end of each cultivation. The microalgae were isolated in the Mid-Western Region of Brazil cultivated in open pond systems. It was observed that among the six microalgae used in this work, Pseudokirchneriella subcapitata presented the higher maximum specific growth rate (μmax) (0.12 day-1). The microalgae Coelastrum sp. and P. subcapitata were the ones with the highest lipid contents, with approximately 20% of dry mass. The main fatty acid accumulated in these conditions was palmitic acid, with percentages of 59 to 69% for all microalgae evaluated. Other factors that had influenced results from cultivations in open ponds were discussed here.