Effects of Hydrocarbon Additions on Gas-liquid Mass Transfer Coefficients in Biphasic Bioreactors

Silva, Teresa Lopes da,Calado, Vitor,Silva, Nadia,Mendes, Rui L.,Alves, Sebastiao S.,Vasconcelos, Jorge M.T.,Reis, Alberto The Korean Society for Biotechnology and Bioengine 2006 Biotechnology and Bioprocess Engineering Vol.11 No.3

The effects of aliphatic hydrocarbons (n-hexadecane and n-dodecane) on the volumetric oxygen mass transfer coefficient $(k_L\;a)$ were studied in flat alveolar airlift reactor and continuous stirred tank reactors (CSTRs). In the flat alveolar airlift reactor, high aeration rates (>2vvm) were required in order to obtain efficient organic-aqueous phase dispersion and reliable $k_La$ measurements. Addition of 1% (v/v) n-hexadecane or n-dodecane increased the $k_La$ 1.55- and 1.33-fold, respectively, compared to the control (superficial velocity: $25.8{\times}10^{-3}m/s$, sparger orifice diameter: 0.5 mm). Analysis of the gas-liquid interfacial area a and the liquid film mass transfer coefficient $k_L$ suggests that the observed $k_La$ increase was a function of the media's liquid film mass transfer. Addition of 1% (v/v) n-hexadecane or n-dodecane to analogous setups using CSTRs led to a $k_La$ increase by a factor of 1.68 and 1.36, respectively (superficial velocity: $2.1{\times}10^{-3}m/s$, stirring rate: 250 rpm). These results propose that low-concentration addition of oxygen-vectors to aerobic microbial cultures has additional benefit relative to incubation in purely aqueous media.

Multi-parameter Flow Cytometry as a Tool to Monitor Heterotrophic Microalgal Batch Fermentations for Oil Production Towards Biodiesel

Teresa Lopes da Silva,Carla Amarelo Santos,Alberto Reis 한국생물공학회 2009 Biotechnology and Bioprocess Engineering Vol.14 No.3

Multi-parameter flow cytometry was used to monitor cell intrinsic light scatter, viability, and lipid content of Chlorella protothecoides cells grown in shake flasks. Changes in the right angle light scatter (RALS) and forward angle light scatter (FALS) were detected during the microalgal growth, which were attributed to the different microalgal cell cycle stages. The proportion of cells not stained with PI (cells with intact cytoplasmic membrane) was high (> 90%) during the microalgal growth, even in the latter stationary phase, suggesting that the microalgal cells built-up storage materials which allowed them to survive under nutrient starvation, maintaining their cytoplasmic membranes intact. A high correlation between the Nile Red fluorescence intensity measured by flow cytometry and total lipid content assayed by the traditional lipid extraction method was found for this microalga, making this method a suitable and quick technique for the screening of microalgal strains for lipid production, optimization of biofuel production bioprocesses, and scale-up studies. The highest oil content (~28% w/w dry cell weight, estimated by flow cytometry) was observed in the latter stationary phase. In addition, C.protothecoides oil also depicted the adequate fatty acid methyl ester composition for biodiesel purposes at this growth phase, suggesting that the microalgal oil produced during the latter stationary phase could be an adequate substitute for diesel fuel. Medium growth optimization for enhancement of microalgal oil production is now in progress, using the multi-parameter approach Multi-parameter flow cytometry was used to monitor cell intrinsic light scatter, viability, and lipid content of Chlorella protothecoides cells grown in shake flasks. Changes in the right angle light scatter (RALS) and forward angle light scatter (FALS) were detected during the microalgal growth, which were attributed to the different microalgal cell cycle stages. The proportion of cells not stained with PI (cells with intact cytoplasmic membrane) was high (> 90%) during the microalgal growth, even in the latter stationary phase, suggesting that the microalgal cells built-up storage materials which allowed them to survive under nutrient starvation, maintaining their cytoplasmic membranes intact. A high correlation between the Nile Red fluorescence intensity measured by flow cytometry and total lipid content assayed by the traditional lipid extraction method was found for this microalga, making this method a suitable and quick technique for the screening of microalgal strains for lipid production, optimization of biofuel production bioprocesses, and scale-up studies. The highest oil content (~28% w/w dry cell weight, estimated by flow cytometry) was observed in the latter stationary phase. In addition, C.protothecoides oil also depicted the adequate fatty acid methyl ester composition for biodiesel purposes at this growth phase, suggesting that the microalgal oil produced during the latter stationary phase could be an adequate substitute for diesel fuel. Medium growth optimization for enhancement of microalgal oil production is now in progress, using the multi-parameter approach

Effects of Hydrocarbon Additions on Gas-liquid Mass Transfer Coefficients in Biphasic Bioreactors

Alberto Reis,Teresa Lopes da Silva,Vitor Calado,Nadia Silva,Rui L. Mendes,Sebastiao S. Alves,Jorge M. T. Vasconcelos 한국생물공학회 2006 Biotechnology and Bioprocess Engineering Vol.11 No.3

The effects of aliphatic hydrocarbons (n-hexadecane and n-dodecane) on the volumetric oxygen mass transfer coefficient (kLa) were studied in flat alveolar airlift reactor and continuous stirred tank reactors (CSTRs). In the flat alveolar airlift reactor, high aeration rates (>2 vvm) were required in order to obtain efficient organic-aqueous phase dispersion and reliable kLa measurements. Addition of 1% (v/v) n-hexadecane or n-dodecane increased the kLa 1.55- and 1.33-fold, respectively, compared to the control (superficial velocity: 25.8 × 10-3 m/s, sparger orifice diameter: 0.5 mm). Analysis of the gas-liquid interfacial area a and the liquid film mass transfer coefficient kL suggests that the observed kLa increase was a function of the media’s liquid film mass transfer. Addition of 1% (v/v) n-hexadecane or n-dodecane to analogous setups using CSTRs led to a kLa increase by a factor of 1.68 and 1.36, respectively (superficial velocity: 2.1 × 10-3 m/s, stirring rate: 250 rpm). These results propose that low-concentration addition of oxygen-vectors to aerobic microbial cultures has additional benefit relative to incubation in purely aqueous media.

Are home-based exercises effective to reduce blood pressure in hypertensive adults? A systematic review

Gabriel Dias Rodrigues,Ligia Soares Lima,Nicole Cristine Simões da Silva,Paula Gomes Lopes Telles,Teresa Mell da Mota Silva Rocha,Victor Quintella de Aragão Porto,Viviane Veloso Cardoso,Pedro Paulo da 대한고혈압학회 2022 Clinical Hypertension Vol.28 No.-

Sedentarism and chronic non-communicable diseases have been a worldwide health problem that is drastically exacerbated by the COVID-19 pandemic social impacts. Home-based exercises are widely encouraged during social isolation to counterbalance the physical inactive impacts. Although, in the context of hypertension, are home-based exercises effective in blood pressure controlling? Our objective is to conduct a systematic review of high-quality controlled trials comparing the possible effects of different types of home-based exercises in hypertensive patients. The literature search was carried out in three scientific databases: Medline, Europe PMC, and Lilacs. Articles were included following three criteria: analyzing the effect of home-based exercise programs on blood pressure in treated and untreated hypertensive patients; exercises must perform at home and on the frequency, intensity, time, and type (FITT) principle, and the articles were published in English. From the qualitative analysis of 27 original trials screened through 451 identified studies, the main results are the following: 1) both endurance, isometric strength, and respiratory home-based exercise programs were efficient to decrease blood pressure in hypertensive patients; 2) differences in methodological approaches regarding FITT components, distinct blood pressure values at baseline and specific underlying mechanisms must be considered as a potential bias of each home-based interventions. In conclusion, endurance, isometric strength, and breathing home-based programs seems to be effective to reduce blood pressure in hypertensive patients. However, further randomized controlled trials and mechanistic studies must be performing to guide evidence-based recommendations of home-based exercises as antihypertensive therapy.