Effect of fermentation on the physicochemical characteristics and sensory quality of Arabica coffee.

This work aims to assess the physicochemical characteristics and final sensory quality of Yellow Catuai IAC 62 Arabica coffee fermented with Saccharomyces cerevisiae. For such a purpose, a Composite Central Rotational Design (CCRD) was performed to investigate how fermentation time,temperature and pH conditions, moisture content and concentration of sugars and organic acids affect its sensory quality on two different roast levels in accordance with Specialty Coffee Association (SCA) protocols. It was found that fructose concentration decreased from 12 g/L to around 5 g/L during fermentation, regardless of temperature condition. Furthermore, longer fermentation times and higher temperatures have lowered sucrose and glucose concentrations from 4 to 2 g/L and 7 g/L to zero, respectively. Glycerol concentration was higher as time and temperature increased, and optimal conditions ranged at temperatures between 24 °C and 32 °C from 35 to 45 h of fermentation time. pH decreased as fermentation time elapsed, but there was a more significant reduction due to higher temperatures, starting at around pH 5 and, lower than 4 under extreme conditions. Contents of organic acids such as acetic, propionic, succinic, and lactic acids, were measured at the final stage of each fermentation process under studied conditions. It was observed that coffee samples achieved final scores ranging from 81 to 85 (SCA score), even in longer times and extreme temperature conditions, thus all samples have been classified as specialty coffees. This work described the initial step towards parameterizing fermentation processes, given that the response variables of temperature and fermentation time, were optimal and enhanced the sensory quality of coffee as beverage. Saccharomyces cerevisiae, a commercial product which has already been made available for producers, can ensure an increase in the sensory quality of coffee.

Immobilization of ß-galactosidase from Bacillus licheniformis for application in the dairy industry.

The food industry has developed a wide range of products with reduced lactose to allow people with intolerance to consume dairy products. Although ß-galactosidase has extensive applications in the food, pharma, and biotechnology industries, the enzymes are high-cost catalysts, and their use makes the process costly. Immobilization is a viable strategy for enzyme retention inside a reactor, allowing its reuse and application in continuous processes. Here, we studied the immobilization of ß-galactosidase from Bacillus licheniformis in ion exchange resin. A central composite rotational design (CCRD) was proposed to evaluate the immobilization process in relation to three immobilization solution variables: offered enzyme activity, ionic strength, and pH. The conditions that maximized the response were offered enzyme activity of 953 U, 40 mM ionic strength, and pH 4.0. Subsequently, experiments were performed to provide additional stabilization for biocatalyst, using a buffer solution pH 9.0 at 25 °C for 24 h, and crosslinking with different concentrations of glutaraldehyde. The stabilization step drastically impacted the activity of the immobilized enzyme, and the reticulation with different concentrations of glutaraldehyde showed significant influence on the activity of the immobilized enzyme. In spite of substantially affecting the initial activity of the immobilized enzyme, higher reagent concentrations (3.5 g L-1) were effective for maintaining stability related to the number of cycles of the enzyme immobilized. The ß-galactosidase from Bacillus licheniformis immobilized in Duolite A568 is a promising technique to produce reduced or lactose-free dairy products, as it allows reuse of the biocatalyst, decreasing operational costs.Key Points• Immobilization of ß-galactosidase from Bacillus licheniformis in batch reactor• Influence of buffer pH and ionic concentration and offered enzyme activity on immobilization• Influence of glutaraldehyde on operational stability.

High Gravity and Very High Gravity Fermentation of Sugarcane Molasses by Flocculating Saccharomyces cerevisiae: Experimental Investigation and Kinetic Modeling.

Substantial progress has been made in ethanol fermentation technology under high gravity (HG) and very high gravity (VHG), which offer environmental and economic benefits. HG and VHG processes increase the productivity of ethanol, reduce distillation costs, and enable higher yields. The aim of the present study was to evaluate the use of sugarcane molasses as the medium component along with flocculating yeasts for fermentation in a fed-batch process employing this promising technology. We evaluated fed-batch fermentation, HG, and VHG involving a molasses-based medium with high concentrations of reducing sugars (209, 222, and 250 g/L). Fermentation of 222 g/L of total reducing sugars achieved 89.45% efficiency, with a final ethanol concentration of 104.4 g/L, whereas the highest productivity (2.98 g/(L.h)) was achieved with the fermentation of 209 g/L of total reducing sugars. The ethanol concentration achieved with the fermentation of 222 g/L of total reducing sugars was close to the value obtained for P'max (105.35 g/L). The kinetic model provided a good fit to the experimental data regarding the fermentation of 222 g/L. The results revealed that sugarcane molasses and flocculating yeasts can be efficiently used in HG fermentation to reduce the costs of the process and achieve high ethanol titers.

Lipases: sources, immobilization methods, and industrial applications.

Enzymes are natural catalysts highly specific to the substrate type and operate under mild conditions of temperature, pressure, and pH with high conversion rates, which makes them more efficient than conventional chemical catalysts. The enzymes can be obtained from various sources, animal, vegetable, and microbiological. Lipases are very versatile enzymes, and this has aroused the interest of the industries. However, the great problem of the use of soluble lipases is the high cost of acquisition, low operational stability, and difficulties of recovery, and reuse. Enzymatic immobilization has been suggested as an alternative to reduce the limitations of soluble enzymes, increasing their stability and facilitating recovery, and reuse, significantly reducing the cost of processes involving the use of enzymes. This review presents a discussion on the different immobilization methods for lipase, as well as the challenges of use lipases immobilized on the industrial scale.

Alcoholic fermentation with flocculant Saccharomyces cerevisiae in fed-batch process.

Studies have been conducted on selecting yeast strains for use in fermentation for ethanol production to improve the performance of industrial plants and decrease production costs. In this paper, we study alcoholic fermentation in a fed-batch process using a Saccharomyces cerevisiae yeast strain with flocculant characteristics. Central composite design (CCD) was used to determine the optimal combination of the variables involved, with the sucrose concentration of 170 g/L, a cellular concentration in the inoculum of 40% (v/v), and a filling time of 6 h, which resulted in a 92.20% yield relative to the theoretical maximum yield, a productivity of 6.01 g/L h and a residual sucrose concentration of 44.33 g/L. With some changes in the process such as recirculation of medium during the fermentation process and increase in cellular concentration in the inoculum after use of the CCD was possible to reduce the residual sucrose concentration to 2.8 g/L in 9 h of fermentation and increase yield and productivity for 92.75% and 9.26 g/L h, respectively. A model was developed to describe the inhibition of alcoholic fermentation kinetics by the substrate and the product. The maximum specific growth rate was 0.103 h(-1), with K(I) and K(s) values of 109.86 and 30.24 g/L, respectively. The experimental results from the fed-batch reactor show a good fit with the proposed model, resulting in a maximum growth rate of 0.080 h(-1).