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•Laccase stably grafted on SBA-15 mesoporous silica using surface NH2 groups.•Outstanding catalytic activity in the degradation of several model PAHs.•Aminoalkyl linkages are ...preferred over aminophenyl linkages.•Activity close to that provided by free enzyme.•Nature of the NH2 linkage affects the stability and reusability of the biocatalyst.
A covalent immobilization method based on glutaraldehyde and amino-functionalized SBA-15 supports has been successfully applied to covalently and stably immobilize laccase from Trametes versicolor. The resultant biocatalysts displayed high incorporation yields of enzyme and led to excellent biodegradation rates of selected HPAs models, i.e. naphthalene, phenanthrene and anthracene, in water. The nature of the hydrocarbon chain accompanying the amino group has been shown as determinant for the immobilization as well as for the activity and reusability of the materials. Thus, alkyl moieties displayed higher enzyme loadings than phenyl moieties, being more adequate the larger n-butyl tethering residue likely due to its higher mobility. Using the aminobutyl-based laccase-SBA-15, 82%, 73%, and 55% conversion of naphthalene, phenanthrene and anthracene, respectively, were achieved after 48h, very close to the values obtained with free laccase under the same reaction conditions. On the other hand, aminopropyl-based laccase-SBA-15 biocatalysts displayed the best reusability properties, retaining higher activity after four repeated uses than the corresponding aminobutyl-based materials.
The purpose of this work is to define optimal growth conditions to maximise biomass for batch culture of the cyanobacterium
and the microalgae
and
. Thus, we study the effect of three variables on ...cell growth: i.e., inoculum:culture medium volume ratio (5:45, 10:40, 15:35 and 20:30 mL:mL), light:dark photoperiod (8:16, 12:12 and 16:8 h) and type of culture medium, including both synthetic media (Guillard's F/2 and Walne's) and wastewaters. The results showed that the initial inoculum:culture medium volume ratio, within the range 5:45 to 20:30, did not affect the amount of biomass at the end of the growth (14 days), whereas high (18 h) or low (6 h) number of hours of daily light was important for cell growth. The contribution of nutrients from different culture media could increase the growth rate of the different species.
was favoured in seawater enriched with Guillard's F/2 as well as
and
but in freshwater medium.
had the greatest growth in the marine environment enriched with Walne's media. Nitrogen was the limiting nutrient for growth at the end of the exponential phase of growth for
and
, while iron was for
and
. The growth in different synthetic culture media also determines the biochemical composition of each of the microalgae. All species demonstrated their capability to grow in effluents from a wastewater treatment plant and they efficiently consume nitrogen, especially the three microalga species.
The clopidogrel bisulfate was degraded under aerobic conditions by two bacterial strains isolated from industrial effluents in El-Harrach, Algeria. The sequencing of their 16S rRNA revealed that ...these two strains are Pseudomonas aeruginosa and Pseudomonas putida. The experiments showed that this consortium could remove clopidogrel bisulfate at high concentrations (5–1500 mg·L−1) within 96 h incubation period. The HPLC analysis recorded 75.23% degradation of clopidogrel bisulfate at an initial concentration of 100 mg·L−1 after five days of incubation at pH 7.0 and a temperature of 30 °C. Also, a maximum degradation of 99.08% was carried out at a more basic pH (8.5). While only 41% was degraded at a temperature of 20 °C. Moreover, the presence of supplemental sources of carbon and nitrogen in the mixed culture media effectively improved the biodegradation of clopidogrel bisulfate by the stains. Finally, the morphology of the strains and the properties of the cell's surface were studied using a scanning electron microscope (SEM). This study reports, for the first time, the viability of the aerobic biodegradation of clopidogrel bisulfate in water in a wide range of concentrations.
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•A mixed culture composed of two bacterial strains was able to degrade clopidogrel bisulfate.•The biotreatment process was optimized.•The optimum pH and temperature were 7.0 and 30 °C, respectively.•The presence of organic cosubstrate enhanced the degradation of clopidogrel bisulfate.•The half-life of clopidogrel bisulfate was short at a laboratory scale.
The production of fatty acids ethyl esters (FAEEs) to be used as biodiesel from oleaginous microalgae shows great opportunities as an attractive source for the production of renewable fuels without ...competing with human food. To ensure the economic viability and environmental sustainability of the microbial biomass as a raw material, the integration of its production and transformation into the biorefinery concept is required. In the present work, lipids from wet Isochrysis galbana microalga were extracted with ethyl acetate with and without drying the microalgal biomass (dry and wet extraction method, respectively). Then, FAEEs were produced by lipase-catalyzed transesterification and esterification of the extracted lipids with ethanol using lipase B from Candida antarctica (CALB) and Pseudomonas cepacia (PC) lipase supported on SBA-15 mesoporous silica functionalized with amino groups. The conversion to FAEEs with CALB (97 and 85.5 mol% for dry and wet extraction, respectively) and PC (91 and 87 mol%) biocatalysts reached higher values than those obtained with commercial Novozym 435 (75 and 69.5 mol%). Due to the heterogeneous nature of the composition of microalgae lipids, mixtures with different CALB:PC biocatalyst ratio were used to improve conversion of wet-extracted lipids. The results showed that a 25:75 combi-lipase produced a significantly higher conversion to FAEEs (97.2 mol%) than those produced by each biocatalyst independently from wet-extracted lipids and similar ones than those obtained by each lipase from the dry extraction method. Therefore, that optimized combi-lipase biocatalyst, along with achieving the highest conversion to FAEEs, would allow improving viability of a biorefinery since biodiesel production could be performed without the energy-intensive step of biomass drying.
Abstract
This study evaluates the ability of two bacterial consortia (C2PL05 and BOS08), extracted from very different environments, to degrade low- (naphthalene, phenanthrene, anthracene) and high- ...(pyrene, perylene) molecular-weight polycyclic aromatic hydrocarbons (PAHs) at high (15–25 °C) and low (5–15 °C) temperature ranges. C2PL05 was isolated from a soil in an area chronically and heavily contaminated with petroleum hydrocarbons and BOS08 from decomposing wood in an unpolluted forest, free of PAHs. Bacterial consortia were described by cultivable and noncultivable techniques (denaturing gradient gel electrophoresis). Fungal DNA was not observed within the wood-decomposing consortium and fungal activity was therefore negligible during most of the PAH degradation process. PAH-degrading bacterial populations, measured by most probable number enumeration, increased during the exponential phase. Toxicity estimated by the Microtox method was reduced to low levels and final PAH depletion, determined by HPLC, confirmed the high degree (54% and 99%, respectively) of low- and high-molecular-weight PAH degradation capacity of the two consortia. PAH-degrading capacity was also confirmed at low temperatures, and especially by consortium BOS08 not previously exposed to those toxic compounds, where strains of Acinetobacter sp., Pseudomonas sp., Ralstonia sp. and Microbacterium sp. were identified.
This study consists of the development and optimisation of the potassium hydroxide-catalysed synthesis of fatty acid methyl esters (FAME) from waste cooking oil. A factorial design of experiments and ...a central composite design have been used. The variables chosen were fatty acid concentration in the waste cooking oil, temperature and initial catalyst concentration by weight of waste cooking oil, while the responses were FAME purity and yield. The initial catalyst concentration is the most important factor, having a positive influence on FAME purity, but a negative one on FAME yield due to the positive influences of the yield losses (triglyceride saponification and methyl ester dissolution in glycerol). Fatty acid concentration in the waste cooking oil is the second factor of importance, having negative influences in FAME purity and yield. Temperature has an insignificant effect on FAME purity, but it has a significant negative influence on FAME yield due to the positive effect of temperature on the yield losses. Second-order models were obtained to predict the responses analysed as a function of these variables.
A new biorefinery from Arthrospira platensis was proposed to obtain phycocyanin (PC) and a biocrude by hydrothermal liquefaction (HTL). PC is a high-added-value phycobiliprotein widely used as a food ...colorant and in the nutraceutical and pharmaceutical industries. However, the use of conventional solvents in the extraction process and the purity grade of the extract are shortcomings in bioproduct production. PC was extracted using a reusable ionic liquid EMIMEtSO4, achieving a PC purity of the lowest commercial grade. Therefore, two downstream processes were applied: (1) dialysis + precipitation and (2) aqueous two-phase system (ATPS) + dialysis + precipitation. After the second purification process, the PC purity increased remarkably to reach the analytical grade for pharmaceutical and nutraceutical applications. The waste biomass (WB) obtained in the PC extraction was valorized by hydrothermal liquefaction (HTL) to produce a biocrude. The biocrude yield and composition remarkably enhanced using isopropanol at 350 °C as a cosolvent.
Pseudo-persistent organic pollutants, such as anionic surfactants (AS), are nowadays among the more complex problems that threaten the aquatic environments and other environmental compartments. The ...present work describes the identification and efficiency of a consortium, isolated from Algerian industrial wastewater, to remove three anionic surfactants (i.e., sodium dodecylbenzenesulfonate (SDBS), sodium dodecyl sulfate (SDS) and sodium lauryl ether sulfate (SLES)). The genetic analysis of 16S rRNA indicated that these strains are Alcaligenes faecalis, Enterobacter cloacae and Serratia marcescens. Under aerobic conditions, pH 7.0 and optimum temperature of 30 °C, the mixed consortium allowed to degrade 85.1% of initial SDBS amount after 144 h of incubation with half-life of 20.8 h. While E. cloacae and S. marcescens pure strains eliminated 46% and 41% less SDBS respectively. Evenly, SDS was degraded at only 23.71% by A. faecalis strain. However, the degradation capacity of SDS by the consortium was very high (94.2%) with a half-life of 9.8 h. The SLES anionic surfactant showed a lower biodegradation by the consortium (47.53%) due to the presence of ether oxide units in the chemical structure of SLES which induced toxicity to the medium. The investigation of the biodegradation of this type of organic pollutants by microorganisms has recently become a key issue for the environmental protection area.
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•A new consortium of three bacterial strains was used to degrade anionic surfactants;•The optimum temperature for the growth of the bacterial consortium was 30 °C;•The degradation efficiency of the consortium and the pure strains were compared;•The kinetic of the degradation of anionic surfactants by the consortium was proposed.
Wet lipid extraction combined with residual biomass anaerobic digestion are alternatives to reduce the overall energy consumption of biodiesel production from microalgae. Solvents with different ...polarities have been studied to assess dry and wet lipid extraction process from Isochrysis galbana microalga. Ethyl acetate (EA) and a chloroform:methanol (CM) mixture yielded the best lipid extraction results in the dry and wet route with suitable lipid compositions. Fatty acid methyl esters (FAMEs) conversion of dry and wet extracted lipids with these solvents was performed by using both homogeneous (H2SO4) and heterogeneous (resin CT 269) catalysts. FAME production from wet extracted lipids with the EA solvent using the CT-269 resin constitutes an advantageous process because it avoids the water elimination step, and the CT-269 is a heterogeneous commercial catalyst, readily to separate after reaction. Lipid-spent microalga was anaerobically digested, obtaining that waste biomass from the wet extraction with EA had the highest methane yield (310 mL CH4/g volatile solids (VS). Energy balance analysis for FAMEs production with EA solvent (wet route) and heterogeneous catalyst yielded an energy recovery of about 80% in terms of biodiesel and biogas. Therefore, this process constitutes a promising route under an energy-driven microalga biorefinery.
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•Lipid extraction form Isochrysis galbana were studied in dry and wet processes.•Ethyl acetate is a promising extraction solvent for biodiesel and biogas production.•Waste biomass extracted with ethyl acetate is suitable for methane production.•Energy recovery of 80% is obtained in the biodiesel and biogas production.
Phycoerythrin (PE) extraction from Porphyridium sp. was studied employing ultrasound-assisted extraction combined with aqueous mixtures of two imidazolium-based ionic liquids (ILs) simultaneously, ...marking a significant novelty. A face-centred central composite design and response surface optimised PE yield (EPE), considering the effects of ionic liquid concentration (IL), EmimEtSO4/BmimEtSO4 mass ratio (E/B), biomass concentration (BM), and time (t). Improvements in EPE by 300 % and 115 % were achieved compared to a phosphate buffer solution and the freeze-thaw method, respectively. Temperature and pH effects were examined independently, leading to the determination of optimal operating conditions: BM = 10 mg mL−1, IL = 18.6 wt%, E/B = 0.78/0.22, t = 10 min, T = 35 °C, and pH = 7.5. Results indicated the potential for reusing the ILs for at least five consecutive extraction cycles, maintaining an EPE of 94.2 % compared to fresh ones. This underscores the success and innovation of the developed technology in enhancing PE extraction from Porphyridium sp.
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•Combine UAE + ILs aqueous solutions is a feasible method to extract phycoerythrin.•24 Full factorial experimental design is proposed for phycoerythrin extraction.•The most significant factors are concentration of ILs and biomass, following by ILs mixture.•EMIMEtSO4/BMIMEtSO4 mixture improve the extraction of phycoerythrin.•Extracted amount of phycoerythrin was constant by reusing the ILs for four cycles.
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