Controlled pilot development unit-scale fed-batch cultivation of yeast on spruce hydrolysates

Yeast production on hydrolysate is a likely process solution in large-scale ethanol production from lignocellulose. The hydrolysate will be available on site, and the yeast has furthermore been shown to acquire an increased inhibitor tolerance when cultivated on hydrolysate. However, due to over-flow metabolism and inhibition, efficient yeast production on hydrolysate can only be achieved by well-controlled substrate addition. In the present work, a method was developed for controlled addition of hydrolysate to PDU (process development unit)-scale aerobic fed-batch cultivations of Saccharomyces cerevisiae TMB 3000. A feed rate control strategy, which maintains the ethanol concentration at a low constant level, was adapted to process-like conditions. The ethanol concentration was obtained from on-line measurements of the ethanol mole fraction in the exhaust gas. A computer model of the system was developed to optimize control performance. Productivities, biomass yields, and byproduct formation were evaluated. The feed rate control worked satisfactorily and maintained the ethanol concentration close to the setpoint during the cultivations. Biomass yields of 0.45 g/g were obtained on added hexoses during cultivation on hydrolysate and of 0.49 g/g during cultivation on a synthetic medium with glucose as the carbon source. Exponential growth was achieved with a specific growth rate of 0.18 h(-1) during cultivation on hydrolysate and 0.22 h(-1) during cultivation on glucose

Mass Transport of Lignin in Confined Pores

A crucial step in the chemical delignification of wood is the transport of lignin fragments into free liquor; this step is believed to be the rate-limiting step. This study has investigated the diffusion of kraft lignin molecules through model cellulose membranes of various pore sizes (1-200 nm) by diffusion cells, where the lignin molecules diffuse from donor to acceptor cells through a membrane, where diffusion rate increases by pore size. UV-vis spectra of the donor solutions showed greater absorbance at higher wavelengths (similar to 450 nm), which was probably induced by scattering due to presence of large molecules/clusters, while acceptor samples passed through small pore membranes did not. The UV-vis spectra of acceptor solutions show a characteristic peak at around 350 nm, which corresponds to ionized conjugated molecules: indicating that a chemical fractionation has occurred. Size exclusion chromatography (SEC) showed a difference in the molecular weight (M-w) distribution between lignin from the donor and acceptor chambers. The results show that small pore sizes enable the diffusion of small individual molecules and hinder the transport of large lignin molecules or possible lignin clusters. This study provides more detail in understanding the mass transfer events of pulping processes

The circumstances of migrant families raising children with disabilities in five European countries: Updating knowledge and pursuing new research

In 2017, specialists in several fields (health, education, and social work) from five European countries (France, Georgia, Italy, Norway, and Switzerland) established a network to jointly pursue studies on migration and disability. An initial workshop provided an opportunity to discuss their previous individual work and to develop a comparative research project. This article presents the key aspects of the discussion and the resulting plans for collaborative study. First, migrant children with disabilities remain statistically invisible in some countries. Separate policies and systems address their needs as migrants and their needs as persons with disabilities. Second, in all countries covered by the research network, there is an important gap between legal norms and the circumstances of migrant families raising children with disabilities. The same holds true for collaboration between public agencies, or between those agencies and NGOs (serving persons with disabilities, migrants, and/or national minorities). Further comparative and cross-disciplinary study must focus on increasing the social participation of children with disabilities and their families through social, educational, and health interventions within an intercultural context

Effect of alkalinity on the diffusion of solvent-fractionated lignin through cellulose membranes

Mass transport of liberated lignin fragments from pits and fiber walls into black liquor is considered a determining step in the delignification process. However, our current understanding of the diffusion of lignin through cellulose and the influential parameter on this process is very limited. A comprehensive and detailed study of lignin mass transport through cellulosic materials is, therefore, of great importance. In this study, diffusion cell methodology is implemented to systematically investigate the transport of fractionated kraft lignin molecules through model cellulose membranes. Pulping is a complex process and lignin is very heterogenous material therefore to perform a more detailed study on lignin diffusion, we included an additional solvent fractionation step. One of the benefits of this method is that the setup can be adjusted to various experimental conditions allowing the complex chemical reactions occurring during pulping, which would affect the mass transfer of lignin, to be avoided. Here, the effects of the alkalinity of the aqueous solution and molecular weight of the kraft lignin molecules on their diffusion were investigated. Additionally,\ua0NMR spectroscopy, size exclusion chromatography, and UV/Vis spectroscopy were used to characterize the starting material and the molecules that passed through the membrane. Lignin molecules detected in the acceptor chamber of the diffusion cells had lower molecular weights, indicating a size fractionation between the donor and acceptor chamber. UV/Vis showed higher concentrations of ionized conjugated kraft lignin molecules in the acceptor chamber, which is a sign of chemical fractionation. This study suggests that the diffusion of lignin through small cellulose pores can be enhanced by decreasing the average molecular weight of the diffusing kraft lignin molecules and increasing alkalinity

The Importance of Being Psychologically Empowered: Buffering the Negative Effects of Employee Perceptions of Leader-Member Exchange Differentiation

Although differentiated relationships among leaders and their followers are fundamental to Leader-Member Exchange (LMX) theory, research provides limited knowledge about whether employees’ responses to individual perceptions of LMX differentiation are uniform. In a field study, we examined whether individual-level psychological empowerment buffers the negative relationship between perceived LMX differentiation and job satisfaction, and found that the negative relationship is strongest under low employee psychological empowerment conditions, as compared to high psychological empowerment. Furthermore, in a multi-wave field study and an experiment, we extended these initial findings by investigating employees’ perceptions of supervisory fairness as a mediator of this moderated relationship. We found that the indirect effect between perceived LMX differentiation and job satisfaction, through supervisory fairness perceptions, is strongest under low employee psychological empowerment, as compared to high psychological empowerment. Collectively, our findings showcase the importance of psychological empowerment as a tool for employees to use to counteract the negative effect of perceived differentiated contexts

Does culture matter? The effects of acculturation on workplace relationships

In spite of immigrants’ growing role in the workforce of the United States and other developed countries, organizational communication research about the experience of immigrant employees in the host culture is still very limited. Drawing on the bidimensional acculturation theory, the purpose of this study was to investigate the association of acculturation of immigrant employees with three types of workplace relationships: leader–member exchange (LMX), coworker, and mentoring relationship. Based on a survey of immigrant employees in a U.S. Midwestern city, the study reveals that the two dimensions of acculturation, adjustment to one’s host culture and retention of one’s original culture, are differentially related to the three types of workplace relationships. Both theoretical and practical implications of these findings are discussed in the study

Critique and Review of Leader-Member Exchange Theory: Issues of Agreement, Consensus, and Excellence

The relationship quality that develops between leaders and those designated as followers is of longstanding interest to researchers and practitioners. The purpose of the present article is to review the more recent developments in the field of leader-member exchange (LMX) theory to identify specific issues related to leader-member agreement and follower consensus that have potentially important theoretical and practical implications. We introduce the concept of LMX excellence, which involves high-quality LMX, high leader-member agreement as well as high group consensus in LMX quality. We outline how leaders and followers' behaviour as well as context can enhance or hinder the development of LMX excellence and conclude with an overview of the practical and theoretical implications as well as future research needs

Leader-member exchange (LMX) differentiation and work outcomes:conceptual clarification and critical review

According to Leader-member Exchange (LMX) theory, leaders develop different quality relationships with followers in their team (termed LMX differentiation). An important theoretical question concerns how different LMX relationships within a team affect followers’ work outcomes. This paper provides a critical review of the concept of LMX differentiation. We propose that the LMX differentiation process leads to patterns of LMX relationships that can be captured by three properties (central tendency, variation, and relative position). We describe a taxonomy illustrating the different ways these properties have been conceptualized and measured. We identify two approaches to LMX differentiation as being a ‘perspective of the team’ (that are shared amongst team members) or a ‘perspective of the follower’ (subjective perceptions unique to each follower). These perspectives lead to different types of measures that predict different outcomes at the individual and team levels. We describe theoretical models employed to explain the effects of LMX differentiation (justice, social comparison and social identity theories). Generally, the lower the within-team variation in LMX or the more a team member’s LMX is higher than the mean team LMX, the better are the work outcomes, but many moderators condition these effects. Finally, we identify some key areas for future research

Willing and able: action-state orientation and the relation between procedural justice and employee cooperation

Existing justice theory explains why fair procedures motivate employees to adopt cooperative goals, but it fails to explain how employees strive towards these goals. We study self-regulatory abilities that underlie goal striving; abilities that should thus affect employees’ display of cooperative behavior in response to procedural justice. Building on action control theory, we argue that employees who display effective self-regulatory strategies (action oriented employees) display relatively strong cooperative behavioral responses to fair procedures. A multisource field study and a laboratory experiment support this prediction. A subsequent experiment addresses the process underlying this effect by explicitly showing that action orientation facilitates attainment of the cooperative goals that people adopt in response to fair procedures, thus facilitating the display of actual cooperative behavior. This goal striving approach better integrates research on the relationship between procedural justice and employee cooperation in the self-regulation and the work motivation literature. It also offers organizations a new perspective on making procedural justice effective in stimulating employee cooperation by suggesting factors that help employees reach their adopted goals