A short review on SSF - an interesting process option for ethanol production from lignocellulosic feedstocks

Simultaneous saccharification and fermentation (SSF) is one process option for production of ethanol from lignocellulose. The principal benefits of performing the enzymatic hydrolysis together with the fermentation, instead of in a separate step after the hydrolysis, are the reduced end-product inhibition of the enzymatic hydrolysis, and the reduced investment costs. The principal drawbacks, on the other hand, are the need to find favorable conditions (e.g. temperature and pH) for both the enzymatic hydrolysis and the fermentation and the difficulty to recycle the fermenting organism and the enzymes. To satisfy the first requirement, the temperature is normally kept below 37 degrees C, whereas the difficulty to recycle the yeast makes it beneficial to operate with a low yeast concentration and at a high solid loading. In this review, we make a brief overview of recent experimental work and development of SSF using lignocellulosic feedstocks. Significant progress has been made with respect to increasing the substrate loading, decreasing the yeast concentration and co-fermentation of both hexoses and pentoses during SSF. Presently, an SSF process for e.g. wheat straw hydrolyzate can be expected to give final ethanol concentrations close to 40 g L-1 with a yield based on total hexoses and pentoses higher than 70%.

Metabolic effects of furaldehydes and impacts on biotechnological processes

There is a growing awareness that lignocellulose will be a major raw material for production of both fuel and chemicals in the coming decades--most likely through various fermentation routes. Considerable attention has been given to the problem of finding efficient means of separating the major constituents in lignocellulose (i.e., lignin, hemicellulose, and cellulose) and to efficiently hydrolyze the carbohydrate parts into sugars. In these processes, by-products will inevitably form to some extent, and these will have to be dealt with in the ensuing microbial processes. One group of compounds in this category is the furaldehydes. 2-Furaldehyde (furfural) and substituted 2-furaldehydes--most importantly 5-hydroxymethyl-2-furaldehyde--are the dominant inhibitory compounds found in lignocellulosic hydrolyzates. The furaldehydes are known to have biological effects and act as inhibitors in fermentation processes. The effects of these compounds will therefore have to be considered in the design of biotechnological processes using lignocellulose. In this short review, we take a look at known metabolic effects, as well as strategies to overcome problems in biotechnological applications caused by furaldehydes.

Modeling simultaneous glucose and xylose uptake in Saccharomyces cerevisiae from kinetics and gene expression of sugar transporters

A kinetic model for glucose and xylose co-substrate uptake in Saccharomyces cerevisiae is presented. The model couples the enzyme kinetics with the glucose-dependent genetic expression of the individual transport proteins. This novel approach implies several options for optimizing the co-substrate utilization. Interestingly, the simulations predict a maximum xylose uptake rate at a glucose concentration >0 g/L, which suggests that the genetic expressions of the considered transport proteins are of importance when optimizing the xylose uptake. This was also evident in fed-batch simulations, where a distinct optimal glucose addition rate >0 g/L x h was found. Strategies for improving the co-substrate utilization by genetic engineering of the transport systems are furthermore suggested based on simulations.

Carbon fluxes of xylose-consuming Saccharomyces cerevisiae strains are affected differently by NADH and NADPH usage in HMF reduction

Industrial Saccharomyces cerevisiae strains able to utilize xylose have been constructed by overexpression of XYL1 and XYL2 genes encoding the NADPH-preferring xylose reductase (XR) and the NAD(+)-dependent xylitol dehydrogenase (XDH), respectively, from Pichia stipitis. However, the use of different co-factors by XR and XDH leads to NAD(+) deficiency followed by xylitol excretion and reduced product yield. The furaldehydes 5-hydroxymethyl-furfural (HMF) and furfural inhibit yeast metabolism, prolong the lag phase, and reduce the ethanol productivity. Recently, genes encoding furaldehyde reductases were identified and their overexpression was shown to improve S. cerevisiae growth and fermentation rate in HMF containing media and in lignocellulosic hydrolysate. In the current study, we constructed a xylose-consuming S. cerevisiae strain using the XR/XDH pathway from P. stipitis. Then, the genes encoding the NADH- and the NADPH-dependent HMF reductases, ADH1-S110P-Y295C and ADH6, respectively, were individually overexpressed in this background. The performance of these strains, which differed in their co-factor usage for HMF reduction, was evaluated under anaerobic conditions in batch fermentation in absence or in presence of HMF. In anaerobic continuous culture, carbon fluxes were obtained for simultaneous xylose consumption and HMF reduction. Our results show that the co-factor used for HMF reduction primarily influenced formation of products other than ethanol, and that NADH-dependent HMF reduction influenced product formation more than NADPH-dependent HMF reduction. In particular, NADH-dependent HMF reduction contributed to carbon conservation so that biomass was produced at the expense of xylitol and glycerol formation.

Prefermentation improves xylose utilization in simultaneous saccharification and co-fermentation of pretreated spruce

BACKGROUND

Simultaneous saccharification and fermentation (SSF) is a promising process option for ethanol production from lignocellulosic materials. However, both the overall ethanol yield and the final ethanol concentration in the fermentation broth must be high. Hence, almost complete conversion of both hexoses and pentoses must be achieved in SSF at a high solid content. A principal difficulty is to obtain an efficient pentose uptake in the presence of high glucose and inhibitor concentrations. Initial glucose present in pretreated spruce decreases the xylose utilization by yeast, due to competitive inhibition of sugar transport. In the current work, prefermentation was studied as a possible means to overcome the problem of competitive inhibition. The free hexoses, initially present in the slurry, were in these experiments fermented before adding the enzymes, thereby lowering the glucose concentration.

RESULTS

This work shows that a high degree of xylose conversion and high ethanol yields can be achieved in SSF of pretreated spruce with a xylose fermenting strain of Saccharomyces cerevisiae (TMB3400) at 7% and 10% water insoluble solids (WIS). Prefermentation and fed-batch operation, both separately and in combination, improved xylose utilization. Up to 77% xylose utilization and 85% of theoretical ethanol yield (based on total sugars), giving a final ethanol concentration of 45 g L-1, were obtained in fed-batch SSF at 10% WIS when prefermentation was applied.

CONCLUSION

Clearly, the mode of fermentation has a high impact on the xylose conversion by yeast in SSF. Prefermentation enhances xylose uptake most likely because of the reduced transport inhibition, in both batch and fed-batch operation. The process significance of this will be even greater for xylose-rich feedstocks.

A prospective study on self-assessed mental well-being and work capacity as determinants of all-cause sickness absence

PURPOSE

The aim of the present study was to estimate whether self-assessed mental well-being and work capacity determines future sickness absence (SA).

METHODS

A questionnaire was sent to employed individuals (n = 6,140), aged 19-64 years, who were registered as sick-listed with a new sick-leave spell in 2008. The response rate was 54 %. In this study we included individuals with a single sick-leave spell in 2008 (n = 2,502). The WHO (Ten) Well-Being Index and four dimensions of self-assessed work capacity (knowledge, mental, collaborative, physical) were used as determinants. Future sickness absence was identified through national register in 2009. Outcome was defined as no sickness benefit compensated days (no SBCD) and at least one sickness benefit compensated day (SBCD). Logistic regression analyses were used to estimate odds ratios (OR) with 95 % confidence intervals (CI) for the likelihood of SBCD.

RESULTS

In 2009, 28 % of the women and 22 % of the men had SBCD; the median was 59 and 66 benefit days, respectively. Individuals with low mental well-being had higher odds for SBCD with OR 1.29 (95 % CI 1.01-1.65) in the fully adjusted model. Participants reporting low work capacity in relation to knowledge (OR 1.55, 95 % CI 1.13-2.13), collaborative (OR 1.36, 95 % CI 1.03-1.79) and physical (OR 1.50, 95 % CI 1.22-1.86) demands at work had higher odds for SBCD after adjustments for all covariates; no relation was demonstrated with mental work capacity (OR 0.99, 95 % CI 0.76-1.27).

CONCLUSION

Mental well-being and work capacity emerged as determinants of future SA. Screening in health care could facilitate early identification of persons in need of interventions to prevent future SA.

Natural filling cystometry in small boys with posterior urethral valves: unstable valve bladders become stable during sleep

PURPOSE

Our aim was to demonstrate the voiding pattern in small boys with posterior urethral valves during the day and night.

MATERIALS AND METHODS

Long-term natural filling and standard cystometry was performed in 16 boys 1.4 to 6 years old (mean age 3.4) in whom posterior urethral valves were diagnosed in infancy. The boys were divided into 2 groups according to whether they had day incontinence.

RESULTS

All boys had instability in the daytime but at night bladders were mainly stable. Voiding frequency during the day was high at a mean of 1.7 and 0.5 voidings per hour in the day incontinent and day continent groups, respectively, compared to 0.1 voiding per hour at night in both groups. Voiding detrusor pressure was higher and functional bladder capacity was lower during the day than at night in both groups.

CONCLUSIONS

Natural filling cystometry revealed pronounced instability during the day and stable bladders at night. This difference between day and night is an important factor contributing to frequent small voidings during the day, dry nights and high bladder volume in the morning.

Managerial preventions of common mental disorders and the association with stigmatizing attitudes

Background

Common mental disorders (CMDs) are an extensive problem in the society and attributed to stigma. Prevention of CMD at work is advocated but few studies have investigated what kind of preventive actions managers take. We investigated managers’ attitudes to depression and two managerial preventive actions (MPA): ‘reviewing assignments and the work situation’ (MPA-review) and ‘taking initiative to talk about depression and anxiety at the workplace’ (MPA-talk). We hypothesized that managers’ negative attitudes towards depression would be negatively associated with both MPAs.

Methods

An on-line survey was sent in 2017 to 4737 managers, answer rate 71% (n = 3358), of which 2 899 were included in this study. Negative attitudes were measured through the 12-item instrument “Managerial stigma towards employee depression” (scores 12-72), a cut-off at the 3rd quartile was used as an indicator for having negative attitudes. MPAs were measured with two single questions. Negative attitudes to depression were analyzed in relation to MPA-review and MPA-talk using binary logistic regression analysis with adjustments for sex, education, managerial experience and training, lived experiences of CMD, work organizational context and general preventive actions in the organization towards CMD.

Results

The proportion of managers with negative attitudes to depression was 20%, performing MPA-review and MPA-talk was 50% and 57% respectively. Adjusted for all co-variates, managers with negative attitudes towards employees with depression were less likely to do both MPA-review (OR 0.71; 95% CI, 0.57-0.89) and MPA-talk (OR 0.53; 95% CI, 0.42-0.66).

Conclusions

Managers with negative attitudes to depression were less likely to take actions to prevent CMD among their employees which confirmed the study hypotheses. The study suggests that initiatives to reduce stigma among managers could be a way forward to prevent CMD at work.

Key messages

• Stigma to depression hampers managers’ prevention of CMD and needs to be addressed.

• To increase managers prevention of CMD, managerial training to reduce stigma towards depression is essential.

Managers’ experience-based understanding of capacity to work in workers with common mental disorders

Background

The capacity to work among workers with common mental disorders (CMD) is important to understand but scarcely explored from a manager perspective, even though their views could add essential knowledge. The aim of this study was to explore and describe managers' experience-based understanding of capacity to work in individuals with CMD.

Methods

This qualitative focus group study used inductive manifest content analysis as analytic technique. First-line managers with experiences of employees with CMDs were recruited via organizations and networks. Eight focus group interviews with altogether 31 participants were performed.

Results

The analysis resulted in five categories of managers' experience-based understanding of occupational functioning in workers with CMDs: (1) The capacity to mentally focus on work tasks decreases or disappears, with negative consequences for work output. (2) The capacity to commit to continuous and coherent tasks changes, making tasks that span over longer periods of time difficult. (3) The capacity to independently adapt to the needs of the situation decreases, causing the worker to need more guidance and instructions than usual. (4) The capacity to keep up professional appearances is reduced, meaning that the worker struggle with the professional role. Finally, (5) the ability to interact socially and professionally decreases, which potentially causes conflicts at the workplace.

Conclusions

This study shows managers' experience-based understanding of CMDs in workers as severe changes and reductions of employees' capacities needed for occupational functioning. These findings add to the understanding of the construction of the capacity at the workplace. A deeper understanding of reduced work capacity is also needed to adapt workplaces and our findings can facilitate work accommodations for employees with CMDs.

Key messages

This study adds a manager perspective to the increasing knowledge about how capacity to work is influenced by CMD. This study shows that managers experience that CMD in workers severely change and reduce employees’ capacities needed for occupational functioning.

Recognition of bladder instability on voiding cystourethrography in infants with urinary tract infection

PURPOSE

We evaluate voiding cystourethrography as a method for identifying bladder instability in infants.

MATERIALS AND METHODS

Cystometry was combined with voiding cystourethrography in 79 male and 64 female infants with first time urinary tract infection. Bladder wall irregularity, elongation of bladder shape, and filling of the posterior urethra were transient radiological signs occurring during bladder filling and were considered to reflect bladder instability. A pediatric radiologist looked for these signs on all 480 films exposed during bladder filling. The results were correlated to simultaneous detrusor pressure recordings. The analysis was repeated independently by a urologist to evaluate the reliability of the radiological signs used.

RESULTS

The sensitivity and specificity were both 90% in the evaluation of radiological signs of bladder instability. Filling of the posterior urethra was the least frequently reported radiological sign, which was seen at 53% of unstable contractions. However, when this sign was reported, instability was usually correctly detected (85%). Evaluation accuracy had improved with increasing numbers of noted signs per film. This accuracy had included 29%, 67% and 91% of unstable contractions that were correctly diagnosed when 1, 2 or 3 signs were noted, respectively. The number of noted signs was positively related to the strength of the unstable detrusor contraction. Urologist evaluations had similar results to the radiologist, although the sensitivity was somewhat lower (79% and 90%, respectively).

CONCLUSIONS

Unstable detrusor contractions could be identified in infants by evaluation of radiological signs on voiding cystourethrography. Findings of bladder wall irregularity, elongation of bladder shape and filling of the posterior urethra indicated unstable detrusor contraction. The more such findings are observed, the stronger the indication.

Managers’ sick-leave recommendations for employees with common mental disorders – a vignette study

Background

To better understand the initial phases of employee sickness absence due to common mental disorders (CMD), this study explores managers' recommendation for sick leave to a CMD-labelled video vignette case. The aim was to investigate the associations between sick leave recommendation and 1) managers' experience of persons with CMD, and 2) managers' previous recommendation of sick leave for employees with CMD, and 3) managers' attitudes toward employees with CMD.

Methods

An online survey was sent in 2017 to 4,737 Swedish managers, aged 20-65 years (71% participated, n = 3,358). The survey included two randomized video vignettes, one female and one male. The vignettes were two minutes long. For aims 1 and 3 a study sample consisting of 2714 managers were used. For the second aim a sub-sample (n = 1740) was used due to the design of the survey questions.

Results

The bi-variate analysis showed that personal experience of CMD was associated with managers' recommendation of employee sick leave. In the adjusted regression model, it became insignificant (p = 0.056). Having previous experience of recommending sick leave to one employee (OR 3.7, 95% C.I. 2.90-4.73), and to several employees (OR 7.1, 95% C.I. 4.27-11.82), were associated with recommending sick leave, adjusted for gender, level of education, years of managerial experience, and having had management training on CMDs. Finally, there was no significant association (p = 0.071) between negative attitudes towards employee depression and managers' recommendation of employee sick leave to the vignette case.

Conclusions

The likelihood of a manager recommending sick leave after watching a CMD-labelled video vignette was higher if the manager had previously experienced this situation in real life. We consider this study being important as a first study looking into managers' attitudes and personal experience and recommendations of sick leave.

Key messages

The odds for recommending sick leave to a video vignette case was higher if managers had this experience. This study highlights the importance of including managerial behaviors to understand the sick leave process for employees with CMD.

Managers’ sick-leave recommendations - a video vignette study on common mental disorders

Background

Sick leave due to common mental disorders (CMD) in Sweden is higher among women than men. Since the Swedish labor market is highly sex segregated a contributing factor might be managers’ attitudes towards CMD and sick leave. This video vignette study tests three hypotheses on managerś sex and recommendation for sick leave. The hypotheses are: (1) there is an association between negative attitudes towards CMDs and recommending sick leave, and (2) there is an association between educational level and recommending sick leave, and (3) there is an association between workplace factors and managerś recommendation of sick leave.

Methods

The study sample consisted of 2703 Swedish managers, female (34%) and male (66%). The online survey included a randomized female and male video vignette played by actors and specifically designed for the study. Associations were investigated by means of logistic regression. The covariates were attitudes towards depression, educational level, labor sector, size of company, proportion of women/men at the workplace, and sex of the person in the video vignette.

Results

The bi-variate crude analysis showed an OR of 1.28 (95% C.I. 1.08-1.51) for female vs. male managers’ recommendation of employee sick leave to the video vignette. Negative attitudes towards CMD did not add to the model, whereas educational level did, OR 1.34 (95% C.I. 1.13-1.59). The final, fully adjusted model showed an OR of 1.39 (95% C.I. 1.16-1.66) for female vs. male managers’ recommendation of employee sick leave.

Conclusions

The likelihood of a manager recommending sick leave after watching a CMD-labelled video vignette was slightly higher for female managers compared to male, and it remained in the final adjusted model. The results resonate with the registered sick leave and the sex segregation among managers and industries in the Swedish labor market.

Key messages

Which managers make which work accommodations for employees with common mental disorders?

Background

Work accommodations (WAs) can promote employees' decreased work capacity and work participation. However, little is known about how managers make WAs for employees with common mental disorders (CMD). The aim was to investigate managerial determinants for making WAs for employees with CMD.

Methods

An online survey was sent to 4,737 Swedish managers, aged 20-65 years (response rate 71%). Only managers who stated having had employees with CMD in the last two years responded to questions on WAs, and were included in this study (n = 1779). The 15 WAs in the survey were condensed to seven WA types using principal component analysis. We calculated odd ratios (95% confidence intervals) for the association of person- (n = 5), knowledge- (n = 2) and work-related (n = 10) determinants in relation to WA types with multivariate logistic regression, adjusting for managers' personal experience of CMD, medical training, treating people with CMD, type of industry and organizational size.

Results

Greater confidence in how to support employees with CMD was associated with five different WA types, the strongest OR was found for changes in working conditions (OR 1.87 95% CI 1.48 - 2.38). Female manager was associated with three WA types, the strongest OR was found for changes in working conditions (OR 2.09 95% CI 1.60 - 2.73). Managerial training including knowledge about how to support employees with CMD was associated with four WA types, and the strongest OR was found for accommodating work tasks (OR 1.76 95% CI 1.35 -2.28). Only work sector was associated with more than two WA types, where managers in the private sector were less likely to make three WA types.

Conclusions

Greater confident in how to support these employees, being female, managerial CMD-training and working in the public sector were associated with making WAs more often. The findings suggest directions for training managers in making WAs in order to support and improve work capacity of employees with CMD.

Key messages

Managers’ confidence in and knowledge about how to support employees with CMD were essential in order to make work accommodations. Work-related factors were less associated than expected. Training managers to accommodate the work of employees with CMD might be effective.

Determinants of managerial preventive actions in relation to common mental disorders at work

Background

Managers may prevent Common Mental Disorders (CMDs) among their subordinates due to their authority to influence the work environment. Yet, their perspective has received only limited attention in research. This study aims to increase managers’ capacity to contribute to the prevention of CMDs by exploring the determinants of two managerial preventive actions: ’reviewing assignments and the work situation’ (MPA-review) and ’taking initiative to talk about depression and anxiety at work’ (MPA-talk).

Methods

An online survey was sent to 4,737 Swedish managers, aged 20-65 years (71% participated, n = 3,358) in 2017, of which 2,921 were included as they answered the MPA-items. Ten possible determinants of MPAs, comprising person-, work-, and competence-related characteristics of managers were related to performing MPAs (yes or no). Bivariate and multivariate binary logistic regression was performed to test associations (OR with 95% CI) between each determinant and MPAs. We have adjusted for experience-related characteristics of managers and company size.

Results

50% of managers initiated MPA-review and 57% MPA-talk. Managers had a higher odds to initiate respectively MPA-review and MPA-talk when being female (OR 1.42, 95% CI 1.17-1.73; OR 1.33, 95% CI 1.08-1.64), working in organizations offering lectures on CMDs (OR 1.36, 95% CI 1.01-1.83; OR 1.84, 95% CI 1.30-2.60) or stress counselling (OR 1.79, 95% 1.46-2.20; OR 1.53, 95% CI 1.22-1.91), having responsibility for the work environment (OR 1.42, 95% CI 1.15-1.74; OR 1.44, 95% CI 1.16-1.79), or having had received training on CMDs (OR 1.56, 95% CI 1.27-1.93; OR 1.61, 95% CI 1.28-2.03).

Conclusions

Managers report taking more actions to prevent CMDs in their workforce when they are female, have received training on CMDs or work in organisations where CMD preventive measures have been implemented.

Key messages

Organizations could invest in company-wide preventive measures and training to enable MPAs. Managerial education should include information on CMDs in order to improve managers’ preventive capacity.

Managers’ prevention and self-confidence in supporting employees with common mental disorders

Background

Despite managers’ responsibility for work environment and employee health few studies have investigated managers’ actions to prevent common mental disorders (CMD). Concerning prevention of CMD, qualitative studies report managers feeling unconfident. We investigated managers’ self-confidence in supporting employees with CMD and two managerial preventive actions (MPA): ‘reviewing assignments and the work situation’ (MPA-review) and ‘taking initiative to talk about depression and anxiety at the workplace’ (MPA-talk). We hypothesized that managers’ self-confidence in supporting employees with CMD would be positively associated with both MPAs.

Methods

An on-line survey was sent in 2017 to 4737 managers, answer rate 71% (n = 3358), of which 2 899 were included in this study. Both independent and dependent variables were measured through single questions. Self-confidence in supporting employees with CMD was analyzed in relation to MPA-review and MPA-talk using binary logistic regression analysis adjusted for sex, education, managerial experience and training, lived experiences of CMD, work organizational context and general preventive actions in the organization towards CMD.

Results

The proportion of managers with higher self-confidence in supporting employees with CMD was 48.9%, performing MPA-review and MPA-talk was 50% and 57% respectively. Adjusted for all co-variates, managers with higher self-confidence in supporting employees with CMDs were more likely to do both MPA-review (OR 1.57; 95% CI, 1.31-1.87) and MPA-talk (OR 2.06; 95% CI, 1.71-2.25).

Conclusions

The study hypotheses were confirmed. Managers with more self-confidence in supporting employees with CMD were more likely to take actions to prevent CMD, particularly regarding initiating talks about CMD with subordinates. The study suggests it is important to strengthen managers self-confidence in supporting employees with CMD to increase their preventive actions towards CMD.

Key messages

• Managers’ self-confidence in supporting employees with CMD is vital for workplace prevention.

• To strengthen managers’ self-confidence in supporting employees with CMD is essential.

Gender differences in managers’ attitudes toward depressed employees: a cross-sectional study

Background

Depression is known to carry negative attitudes within society and organisations. In the workplace, managers are responsible for the psycho-social work environment and attitudes to depression will likely affect that environment. The few studies performed among managers have found that female, more educated and managers working in the public sector were less likely to report negative attitudes. However, these studies did not take organization characteristics into account. The aim was to investigate the association between gender and negative attitudes toward employees with depression controlling for individual and organisational factors.

Methods

A cross-sectional web-survey was sent to 4737 Swedish managers, aged 20-65 years in 2017, response rate 71%; We included those answering the “Managerial stigma toward employee depression” instrument, n = 2663 (901 women, 1762 men), consisting of 12 items tapping negative attitudes towards depression. The 3rd quartile was used as a cut-off. Multivariate logistic regression analyses on attitudes towards depression were performed (95% CI) to generate odds ratios (OR) adjusted for co-variates (individual and organisational characteristics).

Results

Male managers were more likely to report negative attitudes compared to female managers (OR 1.64, 95% CI 1.28 - 2.10) irrelevant of individual (age, education, current workplace management experience, lifetime experience in management, managerial position) or organisational (work sector, staff gender composition, presence of staff members with Common Mental Disorders) characteristics.

Conclusions

A gender difference in reporting negative attitudes was appraised regardless any of the co-variates included. To manage depression within the workplace, companies should also address managers’ attitudes towards depression.

Key messages

Important to heed managers’ attitudes to CMDs and their impact on RTW processes. Gender-tailored approach in managers’ training is suggested for awareness and knowledge on mental health.