Assessment of toxicity of a biosurfactant from Candida sphaerica UCP 0995 cultivated with industrial residues in a bioreactor

Background: The aim of the present study was to propose a low-cost method for the production of a biosurfactant by the yeast Candida sphaerica and assess its toxicity and phytotoxicity. The medium was formulated with distilled water supplemented with residue from a soy oil refinery (5%) and corn steep liquor (2.5%) as substrates. These two products were the sources of carbon and nitrogen as well as mineral elements to encourage the growth of the microorganism and production of a biosurfactant. Results: The isolated biosurfactant yield was 6.364 g/l. The biosurfactant exhibited an excellent ability to reduce surface tension (26 mN/m) and demonstrated no toxicity against seeds of Brassica oleracea , Chicoria intybus and Solanum gilo or the micro crustacean Artemia salina employed as a bioindicator. The biosurfactant exhibited no antimicrobial activity against the fungi and bacteria tested. Conclusions: The promising results obtained in this study indicate the feasibility of producing biosurfactants from powerful non-toxic organic residues and their application in the bioremediation of contaminated soil and water

Partitioning and extraction protease from Aspergillus tamarii URM4634 using PEG-citrate aqueous two-phase systems

PEG-citrate Aqueous Two-Phase Systems (ATPS) were used to recover and partially purify protease from Aspergillus tamarii URM4634 produced by Solid State Fermentation. Experiments were performed according to a 24-full factorial design using PEG molar mass (MPEG), PEG concentration (CPEG), citrate concentration (CCIT) and pH as independent variables; and purification factor (PF), partition coefficient (K) and activity yield (Y) as responses. Protease showed high activity in the PEG-rich phase, also MPEG and CCIT were shown to exert positive effects on all responses. The highest purification factor (3.95) was obtained using MPEG=8000 g/mol, 24% (w/w) CPEG, 20% (w/w) CCIT at pH 8.0. Consequently, the selected ATPS proved to be efficient and can be used as a first step for pre-purification of protease from solid state fermented of A. tamarii URM4634

Pigments Production, Growth Kinetics, and Bioenergetic Patterns in Dunaliella tertiolecta (Chlorophyta) in Response to Different Culture Media

This work dealt with the study of growth parameters, pigments production, and bioenergetic aspects of the microalga Dunaliella tertiolecta in different culture media. For this purpose, cultures were carried out in Erlenmeyer flasks containing F/2 medium, Bold\u2019s Basal medium, or an alternative medium made up of the same constituents of the Bold\u2019s Basal medium dissolved in natural seawater instead of distilled water. D. tertiolecta reached the highest dry cell concentration (Xmax = 1223 mgDM L 121), specific growth rate (\ub5max = 0.535 d 121), cell productivity (PX = 102 mgDM L 121 d 121), and photosynthetic efficiency (PE = 14.54%) in the alternative medium, while the highest contents of carotenoids (52.0 mg\ub7g 121) and chlorophyll (108.0 mg\ub7g 121) in the biomass were obtained in Bold\u2019s Basal medium. As for the bioenergetic parameters, the biomass yield on Gibbs energy dissipation was higher and comparable in both seawater-based media. However, the F/2 medium led to the highest values of moles of photons absorbed to produce 1 C-mol of biomass (nPh), total Gibbs energy absorbed by the photosynthesis (\u394Ga) and released heat (Q), as well as the lowest cell concentration, thus proving to be the least suitable medium for D. tertiolecta growth. On the other hand, the highest values of molar development of O2 and consumption of H+ and H2O were obtained in the alternative medium, which also ensured the best kinetic parameters, thereby allowing for the best energy exploitation for cell growth. These results demonstrate that composition of culture medium for microalgae cultivation has different effects on pigments production, growth kinetics, and bioenergetics parameters, which should be taken into consideration for any use of biomass, including as raw material for biofuels production