Abstract Conventional production of instant coffee is based on solubilisation of polysaccharides present in roasted coffee. Higher process temperatures increase the solubilisation yield, but also lead to carbohydrate degradation and formation of undesirable volatile compounds. Enzymatic hydrolysis of roasted coffee is an alternative to minimize carbohydrate degradation. In this work, products obtained from thermal and enzymatic processes were compared in terms of carbohydrates and volatiles composition. Roasted coffee was extracted with water at 125 °C, and spent coffee was processed by thermal (180 °C) or enzymatic hydrolysis. Enzymatic hydrolysis experiments were carried out at 50 °C using the commercial enzyme preparations Powercell (Prozyn), Galactomannanase (HBI-Enzymes), and Ultraflo XL (Novozymes). These formulations were previously selected from eleven different commercial enzyme preparations, and their main enzymatic activities included cellulase, galactomannanase, galactanase, and β-glucanase. Enzymatic hydrolysis yield was 18% (dry basis), similar to the extraction yield at 125 °C (20%), but lower than the thermal hydrolysis yield at 180 °C (28%). Instant coffee produced by enzymatic hydrolysis had a low content of undesirable volatile compounds and 21% (w/w) of total carbohydrates. These results point to the enzymatic process as a feasible alternative for instant coffee production, with benefits including improved quality as well as reduced energy consumption.

Abstract The performance of an in-situ capacitance sensor for on-line monitoring of biomass concentration was evaluated for some of the most important microorganisms in the biotechnology industry: Escherichia coli, Saccharomyces cerevisiae, Pichia pastoris and Bacillus megaterium. A total of 33 batch and fed-batch cultures were carried out in a bench-scale bioreactor and biomass formation trends were followed by dielectric measurements during the growth phase as well as the induction phase, for 5 recombinant E. coli strains. Permittivity measurements and viable cellular concentrations presented a linear correlation for all the studied conditions. In addition, the permittivity signal was further used for inference of the cellular growth rate. The estimated specific growth rates mirrored the main trends of the metabolic states of the different cells and they can be further used for setting-up control strategies in fed-batch cultures.

High cell density cultivations of recombinant E. coli have been increasingly used for the production of heterologous proteins. However, it is a challenge to maintain these cultivations within the desired conditions, given that some variables such as dissolved oxygen concentration (DOC) and feed flow rate are difficult to control. This paper describes the software SUPERSYS_HCDC, a tool developed to supervise fed-batch cultures of rE. coli with biomass concentrations up to 150 gDCW/L and cell productivities up to 9 gDCW.L-1.h-1. The tool includes automatic control of the DOC by integrated action of the stirrer speed as well as of the air and oxygen flow rates; automatic start-up of the feed flow of fresh medium (system based on a neural network committee); and automatic slowdown of feeding when oxygen consumption exceeds the maximum capacity of the oxygen supply.

This work reports the influence of different culture preservation methods on the production of penicillin G acylase (PGA) by Bacillus megaterium ATCC 14945. The initial stock culture, presenting PGA activity of 97 IU l-1, was preserved for two years using different procedures: monthly subculturing and storage in refrigerator (S), freeze-drying using skim milk 10%, plus inositol 5% as cryoprotectors (L1), freeze-drying using sucrose 7%, plus peptone 7% (L2), and freezing with glycerol 10% (F). After cultivations at standard operational conditions, different values of enzyme activity were obtained: 56 IU l-1 for monthly subculturing (S), 15-41 IU l-1 for freeze-dried cells and frozen spores. All the tested methods have failed in preserving the PGA expression. Among all tested cultures, S presented the highest specific activity, and was used to prepare a standard inoculum in cryovials (-50ºC, frozen spores in a 20% glycerol solution). By cultivation of this inoculum under different conditions, it was found that PGA activity raised to 128 IU l-1 when 0.4 g l-1 of salts was added to the medium.