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Multi‐enzyme reaction systems have become an interesting option to avoid transformation and purification steps in productive reactor‐based systems; when carried out in a single vessel, they are termed one‐pot systems. This novel work aims to model and simulate the behavior of a one‐pot heterogeneous catalysis system in a batch‐stirred bioreactor and in a continuous stirred bioreactor with co‐immobilized enzymes to determine the compromise operation temperature that maximizes the volumetric productivity, considering thermal decay of the biocatalyst. The production of fructose from lactose is considered a case study, using co‐immobilized β ${\beta }$ ‐galactosidase (β ${\beta }$ ‐gal) and glucose‐isomerase (GI) in a spherical particle. A diffusion and reaction mathematical model was used to calculate the effectiveness factor for every reaction species considering the thermal decay of both enzymes. Simulations in both batch and continuous operation were done at temperatures ranging from 40 to 60 °C, for initial enzyme activity load ratios ranging from 0.1 to 0.9 IUGI IUβ-gal-1 ${_{{\rm{{\rm \beta} }}{\kern 1pt} {\rm{ - gal}}{\kern 1pt} }^{ - 1} }$. Resulting effectiveness factors were close to one, indicating no significant limitations on reaction rates due to internal diffusional constraints. In both cases, temperature exerted a more substantial effect than the initial enzyme activity load ratio, showing different scenarios of high volumetric productivity (batch) or amount of produced fructose (continuous). [ABSTRACT FROM AUTHOR]

BACKGROUND Butanol is a versatile chemical that can be used as fuel, solvent or intermediate in chemical synthesis. Several strategies have been used to increase the availability of reducing power in Clostridium sp. with the aim of maximizing the production of butanol, the use of electron carriers being one of the most effective. Moreover, electrons from an external power source can be transferred to cells through electron carriers such neutral red, or directly reducing NAD+. From a previous metabolic analysis, we hypothesized that adding butyrate to the culture medium and using an external electron source as a co‐reducing agent, along with glucose‐derived reducing power (electro‐fermentation), would result in an increase in the specific butanol productivity. RESULTS: Butyrate caused a decrease in the maximum concentration of butanol reached at the concentration used (6 g L−1). The supplementation of neutral red to the culture medium by itself and along with electro‐fermentation were effective in stimulating the production of butanol. The mean specific rate of butanol production obtained for electro‐fermentation in medium supplemented with butyrate and neutral red was 307% and 156% higher than that recorded using medium supplemented with butyrate, or butyrate and neutral red, respectively, this value being even 113% higher than that recorded for the non‐supplemented medium. CONCLUSIONS: The presence of butyrate and absence of neutral red in the electro‐fermentation were detrimental for the microorganism. The electro‐fermentation in medium supplemented with neutral red led to an increase in both volumetric and specific productivities of butanol. © 2021 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

Shelling's model and its different versions predict that segregation is the unique stable equilibrium. However, cities around the world show different levels of intermingle, and it is very uncommon to observe fully segregated urban patterns even when segregation is high. We argue that individuals do not take into account only their neighbours characteristics for making a location decision. In particular, if residential segregation generates ghettos of low-skilled labourers, the societal level of production would diminish and, consequently, individuals’ level of consumption too, affecting all society members’ well-being. When agents care about the impact of segregation on their own consumptions, we prove that the set of system's equilibria can be one containing states of residential integration. Besides, using simulations, we compare the aggregated utility related to these equilibria with the maximum level of aggregated utility. [ABSTRACT FROM AUTHOR]