Petr Kastanek

In-field experimental verification of cultivation of microalgae Chlorella sp. using the flue gas from a cogeneration unit as a source of carbon dioxide

A complex treatment of agricultural waste including the following major steps: anaerobic fermentation of suitable waste, cogeneration of the obtained biogas and growth of microalgae consuming the CO2 from biogas and flue gas was verified under field conditions in a pilot-scale photobioreactor. The growth kinetics of microalgae Chlorella sp. consuming mixture of air and carbon dioxide (2% (v/v) of CO2), or flue gas (8—10% (v/v) of CO2) was investigated. The results obtained in the pilot photobioreactor were compared with results previously measured in laboratory photobioreactors. The field tests were performed in a pilot-scale outdoor solar-bubbled photobioreactor located at a biogas station. The pilot-scale photobioreactor was in the shape of a flat and narrow vertical prism with a volume of 300 L. The microalgae growth rates were correlated with empirical formulas. Laboratory analyses of the produced microalgae confirmed that it meets the strict EU criteria for relevant contaminants level in foodstuffs. Utilization of flue gases from cogeneration therefore was not found to be detrimental to the quality of microalgal biomass, and may be used in these types of bioreactors.

Harvesting freshwater Chlorella vulgaris with flocculant derived from spent brewer's yeast

One of the key bottlenecks of the economically viable production of low added value microalgal products (food supplements, feed, biofuels) is the harvesting of cells from diluted culture medium. The main goals of this work were to prepare a novel flocculation agent based on spent brewers yeast, a brewery by-product, and to test its harvesting efficiency on freshwater Chlorella vulgaris in different environments. The yeast was first autolyzed/hydrolyzed and subsequently chemically modified with 2-chloro-N,N-diethylethylamine hydrochloride (DEAE). Second, optimal dosage of modified spent yeast (MSY) flocculant for harvesting C. vulgaris was determined in culture media of various compositions. It was found that the absence of phosphorus ions decreased (0.4 mg MSY/g biomass), while the presence of algogenic organic matter (AOM) increased (51 mg MSY/g biomass) the required dosage of flocculant as compared to complete mineral medium with phosphorus and without AOM (12 mg MSY/g biomass).

Combination of Advanced Oxidation and/or Reductive Dehalogenation and Biodegradation for the Decontamination of Waters Contaminated with Chlorinated Organic Compounds

Abstract The method of decomposition of chlorinated organic substances in contaminated water based upon successive steps of chemical pretreatment of organic compound with a) active radicals (Fenton reaction) and/or with b) reductive dehalogenation on metallic Pd in the presence of zero‐valent iron, followed by aerobic biodegradation using bacteria strain Pandoraea sp. was studied. 4‐chlorophenol was chosen as a model compound. Generally, chlorophenols show limited biodegradability. The average efficiency of biodegradability of 4‐chlorophenol with both free and immobilized cells does not exceed 70% after 42 days of biodegradation, but their intermediates obtained by partial oxidation (products of hydrolytic‐hydroxylation) and/or a product of their partial reductive dechlorination (phenol) show increased biodegradability. To test the efficiency of the method, water exposed to this contaminant was treated in the laboratory in batch conditions. Because the products of partial oxidation and partial reductive dehalogenation of 4‐chlorophenol essentially differ, the main factor studied was the efficiency of biodegradation of 4‐chlorophenol after oxidative or reductive pre‐treatment steps. In comparison with the rate of biodegradation using free cells without application of the pre‐treatment step, the rate of degradation of 4‐chlorophenol by the application of consecutive combination of Fenton reagent and biotreatment was two‐fold. As for the combination of reductive dechlorination pre‐treatment step with consecutive biodegradation, the rate of decontamination of the 4‐chlorophenol was a little bit higher here in comparison with the rate of biotreatment after the pre‐oxidizing step: the remaining concentration of 4‐chlorophenol corresponding to the sampling in 7, 28, and 56 days after the inoculation were 70 mg/L, 12 mg/L, and 1.1 mg/L, respectively, in samples containing the average initial concentration of 126 mg/L of 4‐chlorophenol. Positive results may probably be due to the co‐substrate effect of phenol presented in the samples after the pre‐traetment reductive step. We have shown that both procedures followed with aerobic biodegradation can be considered suitable for removing hazardous chlorinated compounds from contaminated waters. The rate of biodegradation after the application of pre‐treatment procedures was slightly enhanced in comparison with the rate of biodegradation without the application of the pre‐treatment steps. It is evident that the choice of the decontamination pre‐treatment procedure cannot be generalized and will essentially depend upon the type and concentration of target contaminants and on process costs.

Bioprospecting of microalgae: Proper extraction followed by high performance liquid chromatographic–high resolution mass spectrometric fingerprinting as key tools for successful metabolom characterization

Currently, the interest in microalgae as a source of biologically active components exploitable as supplementary ingredients to food/feed or in cosmetics continues to increase. Existing research mainly aims to focus on revealing and recovering the rare, cost competitive components of the algae metabolom. Because these components could be of very different physicochemical character, a universal approach for their isolation and characterization should be developed. This study demonstrates the systematic development of the extraction strategy that represents one of the key challenges in effective algae bioprospecting, which predefines their further industrial application. By using of Trachydiscus minutus as a model microalgae biomass, following procedures were tested and critically evaluated in order to develop the generic procedure for microalgae bioprospecting: (i) various ways of mechanical disintegration of algae cells enabling maximum extraction efficiency, (ii) the use of a wide range of extraction solvents/solvent mixtures suitable for optimal extraction yields of polar, medium-polar, and non-polar compounds, (iii) the use of consecutive extractions as a fractionation approach. Within the study, targeted screening of selected compounds representing broad range of polarities was realized by ultra-high performance liquid chromatography coupled with high resolution tandem mass spectrometric detection (UHPLC-HRMS/MS), to assess the effectiveness of undertaken isolation steps. As a result, simple and high-throughput extraction-fractionation strategy based on consecutive extraction with water-aqueous methanol-hexane/isopropanol was developed. Moreover, to demonstrate the potential of the UHPLC-HRMS/MS for the retrospective non-target screening and compounds identification, the collected mass spectra have been evaluated to characterize the pattern of extracted metabolites. Attention was focused on medium-/non-polar extracts and characterization of lipid species present in the T. minutus algae. Such detailed information on the composition of native (non-hydrolyzed) lipids of this microalga has not been published yet.

Microwave-Enhanced Thermal Desorption of Polyhalogenated Biphenyls from Contaminated Soil

The effect of microwave (MW) field on the rate of thermal desorption of polychlorinated biphenyls (PCBs) from long-term contaminated soil was examined in the laboratory environment. For these purposes a modified MW oven was used, with a uniformly extended MW field and a power consumption of 200–600 W. The weight of the soil samples was 100 g, the sum of concentrations of seven indicative congeners of PCB Nos. 28, 52, 101, 118, 153, 138, and 180 was, on average, 264 mg/kg of dry matter. It was experimentally proven that the efficiencies of PCB desorptions were high, over 99.9%. The maximal desorption temperature of 600°C was reached within 15–17 min. It came to light that the presence of alkaline additives in the soil (such as carbonates and alkaline metal hydroxides) did not have an apparent effect on the desorption of PCBs under those conditions. The results concerning the efficiency of PCB separations are in agreement with our previous findings regarding the efficiency of thermal desorption without usin...

Characterizing Biochar as Alternative Sorbent for Oil Spill Remediation

Biochar (BC) was characterized as a new carbonaceous material for the adsorption of toluene from water. The tested BC was produced from pine wood gasification, and its sorption ability was compared with that of more common carbonaceous materials such as activated carbon (AC). Both materials were characterized in terms of textural features and sorption abilities by kinetic and equilibrium tests. AC and BC showed high toluene removal from water. Kinetic tests demonstrated that BC is characterized by faster toluene removal than AC is. Textural features demonstrated that the porosity of AC is double that of BC. Nevertheless, equilibrium tests demonstrated that the sorption ability of BC is comparable with that of AC, so the materials’ porosity is not the only parameter that drives toluene adsorption. The specific adsorption ability (mg sorbed m−2 of surface) of the BC is higher than that of AC: toluene is more highly sorbed onto the biochar surface. Biochar is furthermore obtained from biomaterial thermally treated for making energy; this also makes the use of BC economically and environmentally convenient compared with AC, which, as a manufactured material, must be obtained in selected conditions for this type of application.

Erratum to: Selective bioaccumulation of rubidium by microalgae from industrial wastewater containing rubidium and lithium

Bioaccumulation of rubidium (Rb+) and lithium (Li+) from alkaline wastewater containing 480 mg L−1 Rb+ and 540 mg L−1 Li+, a by-product of zinnwaldite processing, was studied at laboratory scale using growing freshwater microalgae (Chlorella vulgaris, Desmodesmus quadricauda and Scenedesmus obliquus). Bioaccumulation of Li+ was very low, while the bioaccumulation of Rb+ was significant by all tested strains. The best result was found for C. vulgaris, which accumulated 54% of the original amount of rubidium in growth media (48 mg L−1) within 4 days. In addition, the wastewater did not affect the growth rate of C. vulgaris. The effect of potassiun (K+) concentration on total bioaccumulation of alkali metal ions and its selectivity by C. vulgaris was also tested. The highest K+ concetration (334 mg L−1) resulted in bioaccumulation of 4.3 mg Rb+ per gram of biomass with Rb+:Li+ uptake ratio of 26.9. By decreasing the K+ concetration in medium (56 mg L−1), the total bioaccumulation improved (4.70 Li+ per gram of biomass, 5.93 Rb+ per gram of biomass) but at the cost of lower selectivity (Rb+:Li+ uptake ratio 1.3). These findings have a potential of practical utilization, as both Rb+ and Li+can be recovered from biomass by incineration and subsequent chemical separation.

Microalgae for bioenergy: key technology nodes.

Microalgae have increasingly gained research interest as a source of lipids for biodiesel production. The wet way processing of harvested microalgae was suggested and evaluated with respect to the possible environmental impacts and production costs. This study is focused on the three key steps of the suggested process: flocculation, water recycling, and extraction of lipids. Microalgae strains with high content of lipids were chosen for cultivation and subsequent treatment process. Ammonium hydroxide was tested as the flocculation agent and its efficiency was compared with chitosan. Determined optimal flocculation conditions for ammonium hydroxide enable the water recycling for the recurring microalgae growth, which was verified for the use of 30, 50, and 80% recycled water. For extraction of the wet microalgae hexane, hexane/ethanol and comparative chloroform/methanol systems were applied. The efficiency of hexane/ethanol extraction system was found as comparable with chloroform/methanol system and it seems to be promising owing to its low volatility and toxicity and mainly the low cost.