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.

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

Effect of medium or high concentrations of in-office dental bleaching gel on the human pulp response in the mandibular incisors

Roderjan Douglas Augusto,Stanislawczuk Rodrigo,Soares Diana Gabriela,de Souza Costa Carlos Alberto,Favoreto Michael Willian,Reis Alessandra,Loguercio Alessandro D. 대한치과보존학회 2023 Restorative Dentistry & Endodontics Vol.48 No.2

Objectives The present study evaluated the pulp response of human mandibular incisors subjected to in-office dental bleaching using gels with medium or high concentrations of hydrogen peroxide (HP). Materials and Methods The following groups were compared: 35% HP (HP35; n = 5) or 20% HP (HP20; n = 4). In the control group (CONT; n = 2), no dental bleaching was performed. The color change (CC) was registered at baseline and after 2 days using the Vita Classical shade guide. Tooth sensitivity (TS) was also recorded for 2 days post-bleaching. The teeth were extracted 2 days after the clinical procedure and subjected to histological analysis. The CC and overall scores for histological evaluation were evaluated by the Kruskal-Wallis and Mann-Whitney tests. The percentage of patients with TS was evaluated by the Fisher exact test (α = 0.05). Results The CC and TS of the HP35 group were significantly higher than those of the CONT group (p < 0.05) and the HP20 group showed an intermediate response, without significant differences from either the HP35 or CONT group (p > 0.05). In both experimental groups, the coronal pulp tissue exhibited partial necrosis associated with tertiary dentin deposition. Overall, the subjacent pulp tissue exhibited a mild inflammatory response. Conclusions In-office bleaching therapies using bleaching gels with 20% or 35% HP caused similar pulp damage to the mandibular incisors, characterized by partial necrosis, tertiary dentin deposition, and mild inflammation. Objectives The present study evaluated the pulp response of human mandibular incisors subjected to in-office dental bleaching using gels with medium or high concentrations of hydrogen peroxide (HP). Materials and Methods The following groups were compared: 35% HP (HP35; n = 5) or 20% HP (HP20; n = 4). In the control group (CONT; n = 2), no dental bleaching was performed. The color change (CC) was registered at baseline and after 2 days using the Vita Classical shade guide. Tooth sensitivity (TS) was also recorded for 2 days post-bleaching. The teeth were extracted 2 days after the clinical procedure and subjected to histological analysis. The CC and overall scores for histological evaluation were evaluated by the Kruskal-Wallis and Mann-Whitney tests. The percentage of patients with TS was evaluated by the Fisher exact test (α = 0.05). Results The CC and TS of the HP35 group were significantly higher than those of the CONT group (p < 0.05) and the HP20 group showed an intermediate response, without significant differences from either the HP35 or CONT group (p > 0.05). In both experimental groups, the coronal pulp tissue exhibited partial necrosis associated with tertiary dentin deposition. Overall, the subjacent pulp tissue exhibited a mild inflammatory response. Conclusions In-office bleaching therapies using bleaching gels with 20% or 35% HP caused similar pulp damage to the mandibular incisors, characterized by partial necrosis, tertiary dentin deposition, and mild inflammation.

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.