Maria Alice Zarur Coelho

Optimization and Modeling of Laccase Production by Trametes versicolor in a Bioreactor Using Statistical Experimental Design

Experimental design and response surface methodologies were applied to optimize laccase production by Trametes versicolor in a bioreactor. The effects of three factors, initial glucose concentration (0 and 9 g/L), agitation (100 and 180 rpm), and pH (3.0 and 5.0), were evaluated to identify the significant effects and its interactions in the laccase production. The pH of the medium was found to be the most important factor, followed by initial glucose concentration and the interaction of both factors. Agitation did not seem to play an important role in laccase production, nor did the interaction agitation x medium pH and agitation x initial glucose concentration. Response surface analysis showed that an initial glucose concentration of 11 g/L and pH controlled at 5.2 were the optimal conditions for laccase production by T. versicolor. Under these conditions, the predicted value for laccase activity was >10,000 U/L, which is in good agreement with the laccase activity obtained experimentally (11,403 U/L). In addition, a mathematical model for the bioprocess was developed. It is shown that it provides a good description of the experimental profile observed, and that it is capable of predicting biomass growth based on secondary process variables.

Decolorization of Dyes from textile wastewater by Trametes versicolor

The white rot fungus Trametes versicolor was applied to the decolourisation of three synthetic textile dyes in the presence and absence of glucose. Different initial dye concentrations were tested and approximately 97% decolourisation was achieved. It was found that fungal metabolism induced by the glucose as well as the pH play an important role in the decolourisation process. This treatment was also applied to a real wastewater from a textile industry-dyeing sector leading to 92% decolourisation.

Biosurfactants from Yeasts: Characteristics, Production and Application

Biosurfactants are surface-active compounds from biological sources, usually extracellular, produced by bacteria, yeast or fungi. Research on biological surfactant production has grown significantly due to the advantages they present over synthetic compounds such as biodegradability, low toxicity, diversity of applications and functionality under extreme conditions. Although the majority of microbial surfactants have been reported in bacteria, the pathogenic nature of some producers restricts the wide application of these compounds. A growing number of aspects related to the production of biosurfactants from yeasts have been the topic of research during the last decade. Given the industrial importance of yeasts and their potential to biosurfactant production, the goal of this chapter is to review the biosurfactants identified up to present, focusing the relevant parameters that influence biosurfactant production by yeasts and its characteristics, revealing the potential of application of such compounds in the industrial field and presenting some directions for the future development of this area, taking into account the production costs.

Cell surface characterization of Yarrowia lipolytica IMUFRJ 50682

In the present work, the surface characteristics of a wild‐type strain of Yarrowia lipolytica (IMUFRJ50682) were investigated. Six different methods to characterize cell surfaces—adhesion to polystyrene; hydrophobic interaction chromatography (HIC); microbial adhesion to solvents (MATS) test; zeta potential; microbial adhesion to hydrocarbons (MATH) test; and contact angle measurement (CAM)—were employed to explain the cell surface behaviour of Y. lipolytica (IMUFRJ50682). This Y. lipolytica strain presents significant differences at the cell surface compared with another Y. lipolytica strain (W29) previously reported in the literature. The main difference is related to the higher cell adhesion to non‐polar solvents. The proteins present on the cell wall of Y. lipolytica IMUFRJ50682 seem to play an important role in these particular surface characteristics because of the consistent reduction of this yeast hydrophobic character after the action of pronase on its cell wall. Copyright

Factorial Design to Optimize Biosurfactant Production by Yarrowia lipolytica

In order to improve biosurfactant production by Yarrowia lipolytica IMUFRJ 50682, a factorial design was carried out. A 24 full factorial design was used to investigate the effects of nitrogen sources (urea, ammonium sulfate, yeast extract, and peptone) on maximum variation of surface tension (ΔST) and emulsification index (EI). The best results (67.7% of EI and 20.9 mN m−1 of ΔST) were obtained in a medium composed of 10 g 1−1 of ammonium sulfate and 0.5 g 1−1 of yeast extract. Then, the effects of carbon sources (glycerol, hexadecane, olive oil, and glucose) were evaluated. The most favorable medium for biosurfactant production was composed of both glucose (4% w/v) and glycerol (2% w/v), which provided an EI of 81.3% and a ΔST of 19.5 mN m−1. The experimental design optimization enhanced ΔEI by 110.7% and ΔST by 108.1% in relation to the standard process.

Produção de biossurfactante por levedura

Biosurfactants are molecules extracellularly produced by bacteria, yeast and fungi that have significant interfacial activity properties. This review focuses on relevant parameters that influence biosurfactant production by yeasts. Many works have investigated the optimization of yeast biosurfactant production, mainly within the last decade, revealing that the potential of such microorganisms is not well explored in the industrial field. The main points to increase the process viability lays on the reduction of the production costs and enhancement of biosynthesis efficiency through optimization the culture conditions (carbon and nitrogen source, pH, aeration, speed agitation) and the selection of inexpensive medium components.

Renewable resources for biosurfactant production by yarrowia lipolytica

In this work, the production of a biosurfactant synthesized by Yarrowia lipolytica using different renewable resources as carbon source was investigated. Crude glycerol, a biodiesel co-product, and clarified cashew apple juice (CCAJ), an agroindustrial residue, were applied as feedstocks for the microbial surfactant synthesis. The microorganism was able to grow and produce biosurfactant on CCAJ and crude glycerol, achieving maximum emulsification indexes of 68.0% and 70.2% and maximum variations in surface tension of 18.0 mN.m-1and 22.0 mN.m-1, respectively. Different organic solvents (acetone, ethyl acetate and chloroform - methanol) were tested for biosurfactant extraction. Maximum biosurfactant recovery was obtained with chloroform - methanol (1:1), reaching 6.9 g.L-1for experiments using CCAJ and 7.9 g.L-1for media containing crude glycerol as carbon source.The results herein obtained indicate that CCAJ and the co-product of biodiesel production are appropriate raw materials for biosurfactant production by Y. lipolytica.

State observers for a biological wastewater nitrogen removal process in a sequential batch reactor

Biological removal of nitrogen is a two-step process: aerobic autotrophic microorganisms oxidize ammoniacal nitrogen to nitrate, and the nitrate is further reduced to elementary nitrogen by heterotrophic microorganisms under anoxic condition with concomitant organic carbon removal. Several state variables are involved which render process monitoring a demanding task, as in most biotechnological processes, measurement of primary variables such as microorganism, carbon and nitrogen concentrations is either difficult or expensive. An alternative is to use a process model of reduced order for on-line inference of state variables based on secondary process measurements, e.g. pH and redox potential. In this work, two modeling approaches were investigated: a generic reduced order model based on the generally accepted IAWQ No. 1 Model [M. Henze, C.P.L., Grady, W., Gujer, G.V.R., Marais, T., Matsuo, Water Res. 21 (5) (1987) 505-515]-generic model (GM), and a reduced order model specially validated with the data acquired from a benchscale sequential batch reactor (SBR) specific model (SM). Model inaccuracies and measurement errors were compensated for with a Kalman filter structure to develop two state observers: one built with GM, the generic observer (GO), and another based on SM, the specific observer (SO). State variables estimated by GM, SM, GO and SO were compared to experimental data from the SBR unit. GM gave the worst performance while SM predictions presented some model to data mismatch. GO and SO, on the other hand, were both in very good agreement with experimental data showing that filters add robustness against model errors, which reduces the modeling effort while assuring adequate inference of process variables.

Assessment of the impact of salinity and irradiance on the combined carbon dioxide sequestration and carotenoids production by Dunaliella salina: A mathematical model

Current anthropogenic activities have been causing a significant increase in the atmospheric concentration of CO2 over the past 60 years. To mitigate the consequent global warming problem, efficient technological solutions, based on economical and technical grounds, are required. In this work, microalgae are studied as important biological systems of CO2 fixation into organic compounds through photosynthesis. These microorganisms are potential sources of a wide variety of interesting chemical compounds, which can be used for commercial purposes, reducing the cost of CO2 capture and sequestration. Specifically, Dunaliella salina culture was studied aiming at the impact evaluation of operational conditions over cellular growth and carotenoid production associated with the CO2 sequestration on focus. The main experimental parameters investigated were salinity and irradiance conditions. The experimental results supported the development of a descriptive mathematical model of the process. Based on the proposed model, a sensitivity analysis was carried out to investigate the operational conditions that maximize CO2 consumption and carotenoid production, in order to guide further development of technological routes for CO2 capture through microalgae. A preliminary cost estimation of CO2 sequestration combined to carotenoids production for a 200 MW power plant is presented, based on the growth rates achieved in this study. Biotechnol. Bioeng. 2009;102: 425–435.

Deposition of Yarrowia lipolytica on plasma prepared teflonlike thin films

Abstract The adhesion of Yarrowia lipolytic a to teflonlike thin films deposited by plasma on polycarbonate substrates was investigated through a series of tests in order to develop a substrate for strong and selective adhesion of Yarrowia lipolytica cells. Teflonlike thin films were prepared using atmospheric pressure surface barrier discharge with mixtures of octafluorocyclobutane (C4F8) and nitrogen as plasma gas. A variety of plasma gas feedrates and different deposition times were studied. The films were characterised by Fourier transform infrared and contact angle measurements using the sessile drop technique. Total surface energy and its components were calculated using the acid base theory. Attachment of the yeast cells was assessed by optical and scanning electron microscopy. The optimal deposition conditions for cell adhesion were determined using standard adhesion tests.