Double T-junction microfluidic and conventional dripping systems for Bacillus subtilis immobilization in calcium alginate microparticles for lipase production.

Bacillus subtilis immobilization in calcium alginate microparticles was investigated using two techniques: droplet microfluidics-based in T-junction geometry composed with a double droplet generation system and conventional dripping system. Alginate microparticles produced by microfluidic technology presented an average size of 68.35 µm with low polydispersity and immobilization efficiency around 86%. The cell response was evaluated in batch cultivation for 24 h, viewing lipase production compared to free cells. In this study, the batch cultivation with immobilized cells in alginate microparticles presented lipase production about 2.4 and 1.7 times higher than cultivation with cells immobilized cells by conventional technique and free cells cultivations. According to the results, this main novelty of the double T junction technique is an innovative contribution as a tool for cell immobilization on a laboratory scale, since the cultivation of immobilized cells in microparticles of small size and low polydispersity favors cell growth and increases the productivity of important metabolites of industrial biotechnology.

Interaction of 4-ethylphenol, pH, sucrose and ethanol on the growth and fermentation capacity of the industrial strain of Saccharomyces cerevisiae PE-2.

Volatile phenols such as 4-ethylphenol are produced from hydroxycinnamic acids by Dekkera bruxellensis, an important yeast contaminating alcoholic fermentations. 4-ethylphenol results from the decarboxylation and reduction of p-coumaric acid, a compound found in sugarcane musts. In wine, volatile phenols are responsible by sensorial alterations whereas in the context of bioethanol fermentation, little is known about their effects on the main yeast, Saccharomyces cerevisiae. Here we evaluated the interaction of 4-ethylphenol and pH, sucrose and ethanol on the growth and fermentation capacity of the industrial strain of S. cerevisiae PE-2. A central compound rotational design was utilized to evaluate the effect of 4-ethylphenol, pH, ethanol and sucrose concentration on the yeast maximum specific growth rate (µmax) in microplate experiments in YPS medium (Yeast extract-Peptone-Sucrose), at 30 °C. Following, single-cycle fermentations in YPS medium, pH 4.5, 17% sucrose, at 30 °C, with 4-ethylphenol in concentrations of 10 and 20 mg L-1 being added at the start or after 4 h of fermentation, were carried out. 4-ethylphenol affected µmax of S. cerevisiae in situations that resemble the conditions of industrial bioethanol production, especially the low pH of the fermentation medium and the high ethanol concentration because of the anaerobic sucrose uptake. The addition of 4-ethylphenol on fermentation resulted in significant effect on the cell yeast concentration, pH and alcohol production, with significant decrease from 86% to the range of 65-74% in the fermentative efficiency. The industrial yeast S. cerevisiae PE-2 growth and fermentative capacity were affected by the presence of 4-ethylphenol, a metabolite produced by D. bruxellensis, which may contribute to explain the impact of this yeast on bioethanol industrial production.

Phycocyanin Production by Aphanothece microscopica Nägeli in Synthetic Medium Supplemented with Sugarcane Vinasse.

This study focused on the evaluation of mixotrophic and heterotrophic production of phycocyanin by A. microscopica, analysis of kinetic parameters, the effect of freezing and thawing on phycocyanin yield, and nutrient removal during heterotrophic growth. During mixotrophic growth, maximum phycocyanin yield (1.50 mgphycocyanin g-1biomass) was obtained after 12 h, while the heterotrophic cultivation yielded 1.39 mgphycocyanin g-1biomass. The mixotrophic cultivation of A. microscopica showed maximum specific growth rate of 0.025 h-1, against 0.010 h-1 for the photoautotrophic cultivation, and 0.08 h-1 in heterotrophic conditions. The mixotrophic cultivation had a specific rate of phycocyanin production of 9.86 mgphycocyanin mgbiomass-1 h-1, while the photoautotrophic had 2.81 mgphycocyanin mgbiomass-1 h-1, and the heterotrophic, 49.18 mgphycocyanin mgbiomass-1 h-1. Carbon and nitrogen contents present in sugarcane vinasse were decreased in 16.69 and 15.97%, respectively, after 6 h of heterotrophic growth. Thus, it was shown that the mixotrophic production of phycocyanin by Aphanothece microscopica Nägeli in BG11 medium supplemented with vinasse is feasible.

Effects of feedstock and co-culture of Lactobacillus fermentum and wild Saccharomyces cerevisiae strain during fuel ethanol fermentation by the industrial yeast strain PE-2.

Even though contamination by bacteria and wild yeasts are frequently observed during fuel ethanol fermentation, our knowledge regarding the effects of both contaminants together is very limited, especially considering that the must composition can vary from exclusively sugarcane juice to a mixture of molasses and juice, affecting the microbial development. Here we studied the effects of the feedstock (sugarcane juice and molasses) and the co-culture of Lactobacillus fermentum and a wild Saccharomyces cerevisiae strain (rough colony and pseudohyphae) in single and multiple-batch fermentation trials with an industrial strain of S. cerevisiae (PE-2) as starter yeast. The results indicate that in multiple-cycle batch system, the feedstock had a minor impact on the fermentation than in single-cycle batch system, however the rough yeast contamination was more harmful than the bacterial contamination in multiple-cycle batch fermentation. The inoculation of both contaminants did not potentiate the detrimental effect in any substrate. The residual sugar concentration in the fermented broth had a higher concentration of fructose than glucose for all fermentations, but in the presence of the rough yeast, the discrepancy between fructose and glucose concentrations were markedly higher, especially in molasses. The biggest problem associated with incomplete fermentation seemed to be the lower consumption rate of sugar and the reduced fructose preference of the rough yeast rather than the lower invertase activity. Lower ethanol production, acetate production and higher residual sugar concentration are characteristics strongly associated with the rough yeast strain and they were not potentiated with the inoculation of L. fermentum.

Microfluidic tools toward industrial biotechnology.

Microfluidics is a technology that operates with small amounts of fluids and makes possible the investigation of cells, enzymes, and biomolecules and encapsulation of biocatalysts in a greater variety of conditions than permitted using conventional methods. This review discusses technological possibilities that can be applied in the field of industrial biotechnology, presenting the principal definitions and fundamental aspects of microfluidic parameters to better understand advanced approaches. Specifically, concentration gradient generators, droplet-based microfluidics, and microbioreactors are explored as useful tools that can contribute to industrial biotechnology. These tools present potential applications, inclusive as commercial platforms to optimizing in bioprocesses development as screening cells, encapsulating biocatalysts, and determining critical kinetic parameters. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1372-1389, 2016.