Extracellular lipase production by Yarrowia lipolytica under magnetic fields.

This study aimed at estimating cultivation conditions to enable Yarrowia lipolytica NNRL Y-1095 to produce extracellular lipase and at evaluating the influence of magnetic fields (MF) on the lipase production and on its catalytic conditions. Culture conditions of carbon sources and surfactant defined to produce extracellular lipase were 10 g L-1 glucose, 15 g L-1 olive oil and 2 g L-1 Triton X-100. The highest lipase activity (34.8 U mL-1) was reached after 144 h when MFs were applied from 72 to 144 h of culture. It corresponds to an increase of 287.5% by comparison with the highest lipase activity in the control culture. MF application from 72 to 144 h did not change the optimal temperature of lipase, which was 37 °C, by comparison with the control. However, the optimal pH of the control was 7.0 while the one of lipase produced with MF was 8.0. Findings highlighted that the presence of MFs led to increase in synthesis of lipase by Y. lipolytica, with changes in the catalytic profile. This is one of the first studies of MF application to Y. lipolytica NRRL Y-1095 cultures to produce lipase.

Magnetic fields as inducer of glutathione and peroxidase production by Saccharomyces cerevisiae.

Glutathione (GSH) and peroxidase (POD) are biomolecules of interest in the global market; thus, it is desirable to seek ways to increase their production. Magnetic field (MF) application is one of the technologies used in cultivation that has shown promising results to increase bioproducts. Therefore, this study aimed at evaluating the influence of MFs on GSH and POD production by Saccharomyces cerevisiae ATCC 7754. Different periods of MF application (35 mT) were evaluated over 72 h. The highest GSH production was reached in 48 h of cultivation in assays MF 0-24 (155.32 ± 9.12 mg L-1) and MF 0-72 (149.27 ± 3.62 mg L-1), which showed an increase of 121.9 % and 113 %, respectively, by comparison with the control without any MF application. The highest POD activity was achieved when MFs were applied throughout the culture (36.31 U mg-1) and POD productivity of 0.72 U mg-1 h-1. MF application throughout cultivation proved to be a promising strategy since all responses increased, i.e., GSH concentration, GSH productivity, POD activity, and POD productivity increased 113.7 %, 113 %, 20.4 %, and 28.6 %, respectively. This study is one of the first to consider MFs as a viable and low-cost alternative to produce GSH and POD in bioprocesses.

Update on the application of magnetic fields to microalgal cultures.

Several studies have shown that any magnetic field (MF) applied to microalgae modifies its cultivation conditions and may favor biomolecule production since it interacts with the microorganisms and affect their growth. As a result, there are changes in concentrations and compositions of biomass and biomolecules. This review aims at updating MF applications to microalga cultures that were reported by studies conducted in the last 5 years. It shows the main studies that reached positive results of carbohydrate, lipid, protein and pigment production. Effects of MFs may be positive, negative or null, depending on some factors, such as intensity, exposure time, physiological state of cells and application devices. Therefore, this review details cultivation conditions used for reaching high concentration of biomolecules, explains the action of MFs on microalgae and describes their applicability to the biorefinery concept.

Differential Effects of Atrazine on Chlorophyceae Species and Association with Morphology, Photosynthesis, Chlorophyll Content, and Glutathione-S-Transferase Activity.

Atrazine is a herbicide widely used in the control of weeds in crops such as corn, sugar cane, and sorghum. It is often found in aquatic environments, where it can potentially endanger nontarget organisms such as microalgae. The present study evaluated atrazine toxicity to seven different species of Chlorophyceae and the tolerance of the species to the herbicide was related to morphological, photosynthetic, chlorophyll-a content and the activity of the glutathione-S-transferase enzyme (GST). The comparison of median effect concentration (EC50) values for growth inhibition indicates higher toxicity of atrazine for Pseudopediastrum boryanum and Desmodesmus communis, intermediate toxicity for Ankistrodesmus densus, Chlamydomonas puliminiorfes, and Raphidocelis subcapitata, and lower toxicity for Kirchneriella lunaris and Ankistrodesmus falcatus (EC50: 38, 42, 66, 103, 248, 1004, and 1585 µg L-1 atrazine, respectively). Principal component analysis (PCA) with algal characteristics suggested that the atrazine-sensitive algae P. boryanum and D. communis were positively associated with photosynthetic levels and negatively associated with GST activity and chlorophyll-a concentration. The PCA also suggested that the atrazine-tolerant algae A. falcatus and K. lunaris were positively associated with morphological parameters, where the larger the cell size, the more tolerant. Although it is difficult to associate a single characteristic of algae as the key factor determining the tolerance to atrazine, results presented in this work indicate that the cell area, the photosynthetic parameters (mainly saturating irradiance), chlorophyll-a content, and the biotransformation by GST in combination may be potential predictors for the differential tolerance of Chlorophyceae species to the herbicide. Environ Toxicol Chem 2022;41:1675-1685. © 2022 SETAC.

Glutathione S-transferase activity in aquatic macrophytes and halophytes and biotransformation potential for biocides.

Glutathione S-transferase (GST) participates in the biotransformation of many xenobiotics including biocides. Its activity in plants is generally associated with their phytoremediation capabilities. Biocides have been used in agriculture and antifouling paints and they represent risks for the aquatic environment. The present study aimed to: (1) evaluate the basal GST activity in roots, stems, and leaves from thirteen plants (eleven aquatic macrophytes and two halophytes) collected at South Brazil wetlands; (2) estimate the biotransformation potential of Nothoscordum gracile for five biocides using competitive kinetic assays with 1-chloro-2,4-dinitrobenzene (CDNB), a typical GST substrate. The N. gracile, Spartina alterniflora and Cakile maritima presented the highest GST activities among the tested plants. The Lineweaver-Burk plot obtained from the GST competitive kinetic assays confirmed that the biocides chlorothalonil, 4,5-dichloro-N-octyl-3(2H)-isothiazolone (DCOIT), dichlofluanid, and diuron, but not irgarol, compete with the substrate CDNB for GST. Chlorothalonil and DCOIT showed the lowest IC20 values (11.1 and 10.6 µM, respectively), followed by dichlofluanid (38.6 µM) and diuron (353.1 µM). The inhibition of GST-CDNB activity by 100 nM biocide was higher for chlorothalonil, DCOIT, and dichlofluanid (46.5, 49.0, and 45.1%, respectively) than for diuron (6.5%) and irgarol (2.2%). The present study indicates plant species that have significant GST activity and could be potentially used for phytoremediation. The competitive kinetic tests suggest that among the five biocides that were tested, chlorothalonil, DCOIT, and dichlofluanid are probably preferred for biotransformation via GST in plant.

Increased lipid synthesis in the culture of Chlorella homosphaera with magnetic fields application.

This study aimed to investigate the influence of different intensities (15, 30 and 60 mT) and exposure times (1 h d-1, 24 h d-1) of magnetic fields (MF) on the stimulation of lipid synthesis by the microalga Chlorella homosphaera. The growth and biochemical characterization of protein, carbohydrate and lipid content were determined. Biomass concentration increased by 20.6% (30 mT, 1 h d-1) and 12.4% (60 mT, 1 h d-1) in the presence of MF. However, biomass decreased by 33.0% (15 mT, 1 h d-1) in relation to control cultivation (CC). The stress caused by the MF application stimulated lipid synthesis and biomass production. In all evaluated conditions, MF application showed a positive effect on lipid production; the application of 60 mT or 30 mT for 1 h d-1 increased lipid productivity by 108.4% and 135.1%, respectively. MF application with ferrite magnets was thus efficient to stimulate lipid synthesis.