Sleep disturbances and semen quality in an Italian cross sectional study

Introduction

In order to obtain information about the relationship between sleep disturbances and sperm parameters, we analyzed data from a study conducted in a Italian Fertility Clinic, in men of couples seeking help for infertility.

Patients and methods

Male partners with or without a medical history of reproductive organ diseases (cryptorchidism, varicocele, orchitis, testicular torsion) were eligible for the study. There were 382 men evaluated from May 2014 to November 2016, all of whom completed a self-administered questionnaire on general lifestyle habits. Then all men underwent semen analysis. A total of 382 men aged 26 to 67 years (median age 39 year interquartile range 37–42) were recruited.

Main results

A total of 46.3% reported having sleep disturbances. In multivariate analysis, in absence of reproductive organ diseases, semen volume was lower in patients with difficulty in initiating sleep (2.0 ml, IQR 1.5–3.0 vs 3.0 ml, IQR 2.0–3.3, p = .01), whereas in presence of reproductive organ diseases motility A was lower in patients with early morning awakening (25.0%, IQR 15.0–35.0 vs. 40.0%, IQR 30.0–50.0, p = .001). In overweight men, semen volume was lower in patients with difficulty in initiating sleep (2.0 ml, IQR 1.5–3.0 vs 3.0 ml, IQR 2.0–3.0, p = .03). Moreover, among current smokers, patients with difficulty in initiating sleep had semen volume lower (1.5 ml, IQR 1.5–2.5 vs 3.0 ml, IQR 2.0–3.5, p = .0003) and sperm concentration higher (40 millions/ml, IQR 15–60 vs 10 millions/ml, IQR 5–50 p = .03) but total sperm count was not significant different.

Conclusion

Further studies are necessary to elucidate the relationship between sleep quality and semen parameters, which may have important public health implication.

     

Genotyping and Persistence of <Emphasis Type="Italic">Candida albicans</Emphasis> from Pregnant Women with Vulvovaginal Candidiasis

Objective

To study Candida albicans genotypes using RAPD and their susceptibility to fluconazole in healthy pregnant women and in vulvovaginal candidiasis (VVC) patients after topical treatment with clotrimazole.

Methods

Vaginal swabs were collected at t = 0 and t = 1 (1 month later) in pregnant women (control group, n = 33), and before (t = 0), at 1 month (t = 1) and at 2 months (t = 2) after clotrimazole treatment in pregnant women with VVC.

Results

Candida albicans was isolated in 30% of healthy pregnant women and 80% of patients with VVC. A high genetic heterogeneity was observed in C. albicans genotypes between individuals. In patients with VVC, topical antifungal treatment with clotrimazole was clinically effective, but only in a 62% C. albicans was eradicated. In patients in which C. albicans was not eradicated, this microorganism persisted for 1 or 2 months after the antifungal treatment. The persistent colonies were not associated with a specific genotype, but they were associated with higher MICs in comparison with colonies isolated from the control group.

Conclusions

Therapy with topical clotrimazole, despite a good clinical outcome, could not eradicate completely C. albicans allowing the persistence of genotypes, with higher MICs to fluconazole. More studies with higher number of patients are needed to validate this preliminary finding.

     

Left ventricular outflow tract velocity time integral outperforms ejection fraction and Doppler-derived cardiac output for predicting outcomes in a select advanced heart failure cohort

Background

Left ventricular outflow tract velocity time integral (LVOT VTI) is a measure of cardiac systolic function and cardiac output. Heart failure patients with low cardiac output are known to have poor cardiovascular outcomes. Thus, extremely low LVOT VTI may predict heart failure patients at highest risk for mortality.

Methods

Patients with heart failure and extremely low LVOT VTI were identified from a single-center database. Baseline characteristics and heart failure related clinical outcomes (death, LVAD) were obtained at 12 months. Correlation between clinical endpoints and the following variables were analyzed: ejection fraction (EF), pulmonary artery systolic pressure (PASP), NYHA class, renal function, Doppler cardiac output (CO), and LVOT VTI.

Results

Study cohort consisted of 100 patients. At the 12-month follow up period, 30 events (28 deaths, 2 LVADs) were identified. Occurrence of death and LVAD implantation was statistically associated with a lower LVOT VTI (p = 0.039) but not EF (p = 0.169) or CO (p = 0.217). In multivariate analysis, LVOT VTI (p = 0.003) remained statistically significant, other significant variables were age (p = 0.033) and PASP (p = 0.022). Survival analysis by LVOT VTI tertile demonstrated an unadjusted hazard ratio of 4.755 (CI 1.576-14.348, p = 0.006) for combined LVAD and mortality at one year.

Conclusions

Extremely low LVOT VTI strongly predicts adverse outcomes and identifies patients who may benefit most from advanced heart failure therapies.

     

Spondylodiskitis and endocarditis due to <Emphasis Type="Italic">Streptococcus gordonii</Emphasis>

Background

Streptococcus gordonii is an infrequent cause of infective endocarditis (IE); associated spondylodiskitis has not yet been described in the literature.

Purpose

We describe 2 patients who presented with new-onset, severe back pain; blood cultures revealed S. gordonii bacteremia, which led to the diagnosis of spondylodiskitis and IE. We review our 2-decade experience with S. gordonii bacteremia to describe the clinical and epidemiological characteristics of these patients.

Results

In our hospital over the last 20 years (1998–2017), a total of 15 patients with S. gordonii bacteremia were diagnosed, including 11 men and 4 women, and the mean age was 65 ± 22 (range 23–95). The most common diagnosis was IE (9 patients), spondylodiskitis (the presented 2 patients, who in addition were diagnosed with endocarditis), necrotizing fasciitis (1), sternitis (1), septic arthritis (1) and pneumonia (1). The 11 patients with IE were treated with penicillin ± gentamicin, or ceftriaxone for 6 weeks, 5 required valve surgery and 10/11 (91%) attained complete cure. The 2 patients with diskitis required 2–3 months of intravenous antibiotics to achieve complete cure.

Conclusion

Spondylodiskitis was the presenting symptom of 2/11 (18%) patients with S. gordonii endocarditis. Spondylodiskitis should probably be looked for in patients diagnosed with S. gordonii endocarditis and back pain as duration of antibiotic treatment to achieve complete cure may be considerably longer.

     

Improved production of carotenoid-free welan gum in a genetic-engineered <Emphasis Type="Italic">Alcaligenes</Emphasis> sp. ATCC31555

Objective

To improve the production of welan gum and obtain a carotenoid-free strain while reducing the fermentation and post-treatment costs.

Results

The vitreoscilla globin (vgb) gene combined with the β-galactosidase (lacZ) promoter was inserted into the phytoene synthase (crtB) gene region of the chromosome in Alcaligenes sp. ATCC31555. When the recombinant strain was grown in a 5 l fermentor, welan gum was produced at 24 ± 0.4 g l^?1 compared to 21 g ± 0.4 g l^?1 in the wild type. Furthermore, the carotenoid-free welan gum produced using Alcaligenes sp. ATCC31555 VHb strain was less expensive with improved properties.

Conclusions

Alcaligenes sp. ATCC31555 VHb strain was a better neutral welan-producing strain with a higher production than the wild-type strain.

     

Association between the blood concentrations of ammonia and carnitine/amino acid of schizophrenic patients treated with valproic acid

Background

Administration of valproic acid (VPA) is complicated with approximately 0.9% of patients developing hyperammonemia, but the pathogenesis of this adverse effect remains to be clarified. The aim of the present study was to search for mechanisms associated with VPA-induced hyperammonemia in the light of changes in serum amino acids concentrations associated with the urea cycle of schizophrenic patients.

Method

Blood samples (10 mL) were obtained from 37 schizophrenic patients receiving VPA for the prevention of violent behaviors in the morning after overnight fast. Blood concentrations of ammonia, VPA, free carnitine, acyl-carnitine, and 40 amino acids including glutamate and citrulline were measured for each patient. Univariate and multivariate regression analyses were performed to identify amino acids or concomitantly administered drugs that were associated with variability in the blood concentrations of ammonia.

Result

The blood ammonia level was positively correlated with the serum glutamate concentration (r = 0.44, p < 0.01) but negatively correlated with glutamine (r = ?0.41, p = 0.01), citrulline (r = ?0.42, p = 0.01), and glycine concentrations (r = ?0.54, p < 0.01). It was also revealed that the concomitant administration of the mood stabilizers (p = 0.04) risperidone (p = 0.03) and blonanserin (p < 0.01) was positively associated with the elevation of the blood ammonia level.

Conclusion

We hypothisized that VPA would elevate the blood ammonia level of schizophrenic patients. The observed changes in serum amino acids are compatible with urea cycle dysfunction, possibly due to reduced carbamoyl-phosphate synthase 1 (CPS1) activity. We conclude that VPA should be prudently prescribed to schizophrenic patients, particularly those receiving mood stabilizers or certain antipsychotics.

     

Expression,purification and characterization of a thermostable leucine dehydrogenase from the halophilic thermophile <Emphasis Type="Italic">Laceyella sacchari</Emphasis>

Objective

A potential thermotolerant l-leucine dehydrogenase from Laceyella sacchari (Ls-LeuDH) was over-expressed in E. coli, purified and characterized.

Results

Ls-LeuDH had excellent thermostability with a specific activity of 183 U/mg at pH 10.5 and 25 °C. It retained a high activity in 200 mM carbonate buffer from pH 9.5 to 11. The optimal temperature for Ls-LeuDH was 60 °C.

Conclusion

It is the first time that a thermostable and highly active LeuDH originating from L. sacchari has been characterized. It may be useful for medical and pharmaceutical applications.

     

High intensity smoking cessation interventions: Cardiac patients of low socioeconomic status and low intention to quit profit most

Background

Without assistance, smokers being admitted to the hospital for coronary heart disease often return to regular smoking within a year.

Objective

This study assessed the 12-month effectiveness of a telephone and a face-to-face counselling intervention on smoking abstinence among cardiac patients. Differential effects for subgroups varying in their socioeconomic status and intention to quit smoking were also studied.

Methods

A randomised controlled trial was used. During hospital stay, smokers hospitalised for coronary heart disease were assigned to usual care (n = 245), telephone counselling (n = 223) or face-to-face counselling (n = 157). Eligible patients were allocated to an intervention counselling group and received nicotine patches. After 12 months, self-reported continued abstinence was assessed and biochemically verified in quitters. Effects on smoking abstinence were tested using multilevel logistic regression analyses applying the intention-to-treat approach.

Results

Compared with usual care, differential effects of telephone and face-to-face counselling on continued abstinence were found in patients with a low socioeconomic status and in patients with a low quit intention. For these patients, telephone counselling increased the likelihood of abstinence threefold (OR = 3.10, 95?% CI 1.32–7.31, p = 0.01), whereas face-to-face counselling increased this likelihood fivefold (OR = 5.30, 95?% CI 2.13–13.17, p < 0.001). Considering the total sample, the interventions did not result in stronger effects than usual care.

Conclusion

Post-discharge telephone and face-to-face counselling interventions increased smoking abstinence rates at 12 months compared with usual care among cardiac patients of low socioeconomic status and low quit intentions. The present study indicates that patients of high socioeconomic status and high quit motivation require different cessation approaches.

     

Exaggerated envy and guilt measured by economic games in Japanese women with anorexia nervosa

Background

Anorexia nervosa (AN) patients are assumed to express high levels of guilt and envy. Ultimatum game (UG) is a standard behavioral task that focuses on interpersonal behavior when splitting a sum of money between two players. UG studies consistently demonstrate that people tend to decrease their inequity in outcomes, one explanation being that economically irrational decision-making may partly arise from the emotions guilt and envy. We assumed that AN patients would perform excessively fair in UG, reflecting high guilt and envy.

Methods

We utilized UG to investigate the characteristics of guilt and envy among 24 Japanese AN patients and 22 age-matched healthy controls (HC). The relation between the outcome of UG and decision strategy confirmed by post-experimental questionnaires was analyzed.

Results

As proposer, AN offered a larger amount to the responder compared with HC (p?=?0.002) while, on the other hand, as responder, AN demanded much higher allocation to accept the offer compared with HC (p?=?0.026). Regarding the strategy as responder, AN put more emphasis on fairness and less emphasis on monetary reward compared with HC (p?=?0.046, p?=?0.042, respectively).

Conclusions

The results indicate that Japanese AN patients demonstrate strong preference for fairness, with high guilt and high envy. High sensitivity to guilt and envy of AN patients can affect not only their own behavior concerning eating attitude and body shape, but also decision-making in interpersonal situations. Behavioral experimental settings among social situations will enable us to evaluate and help actual decision-making in the real life of patients.

     

Evaluation of extracorporeal shock wave therapy for refractory angina pectoris with quantitative analysis using cardiac magnetic resonance imaging: a short communication

Aims

There is a continuing search for new treatment options in patients who suffer from refractory angina pectoris to improve quality of life. Several studies have recently demonstrated promising results by stimulating angiogenesis using extracorporeal shockwave therapy in these patients. The purpose of this study is to quantitatively analyse the effect of extracorporeal shockwave therapy on myocardial perfusion in patients with refractory angina pectoris.

Methods

We included 15 patients with NYHA class 3–4 of whom 8 patients underwent baseline and follow-up cardiac magnetic resonance imaging (CMR). All patients received 9 shockwave treatments of their ischaemic zone over a period of 3 months.

Results

Quantitative analysis of myocardial perfusion using CMR revealed no significant improvement of myocardial perfusion after treatment (0.80 ± 0.22 vs 0.76 ± 0.31; p = 0.42). However, the total group of 15 patients did experience a significant improvement in NYHA class (p = 0.034) and reduction of nitroglycerin use (p = 0.012).

Conclusion

Although treatment with extracorporeal shockwave was associated with an improvement in NYHA class, we could not observe an improvement in myocardial ischaemic zone and perfusion with CMR. To unravel the exact mechanisms of shockwave treatment, more in vitro and animal studies as well as larger (placebo-controlled) studies are required.

     

Introducing transcatheter aortic valve implantation with a new generation prosthesis: Institutional learning curve and effects on acute outcomes

Objectives

We present our single-centre experience with the direct flow medical (DFM) trans-catheter aortic valve implantation (TAVI) prosthesis addressing the impact of learning curve upon outcomes.

Background

The DFM has been recently introduced for TAVI. The prosthesis presents original design and implantation features.

Methods

Patients were divided into three groups according to the chronological implantation sequence that reflected technical skills acquisition of the entire team.

Results

Group I included the first 20 patients (early learning phase), group II the second 20 patients (proctoring to other members of the team), and group III the following 93 patients (technique consolidation). Differences in baseline and procedural variables were analysed. Nonparametric correlation and linear regression were used to identify changes according to institutional cumulative experience. There was a significant correlation between catheterisation time and institutional experience (rho = ?0.4; p < 0.0001) confirmed at linear regression (beta = ?0.2; p = 0.001; CI: ?0.3?–??0.08). Moreover, there was lower rate of valve retrieval in group III (15% vs. 20% vs. 10%; p = 0.5). No intra-procedural mortality was reported and improved early safety (at 30 days) was observed (80% vs. 85% vs. 87.1; p = 0.7). At hospital discharge, valve haemodynamic performance was satisfactory with only mild regurgitation in 10% (I), 20% (II), and 9.7% (III) (p = 0.8).

Conclusions

DFM adequate sizing and implantation can be achieved after the early learning phases. A significant reduction in catheterisation time is reported after the first 20 patients. Results remain satisfactory during the proctoring and technical consolidation phase.

     

Diagnosis of takotsubo cardiomyopathy is increasing over time in patients presenting as ST-elevation myocardial infarction

Background

Takotsubo cardiomyopathy often presents with the clinical signs of ST-elevation myocardial infarction (STEMI). The increase in scientific publications addressing this relatively rare condition may result in higher awareness and diagnosis of takotsubo cardiomyopathy.

Aim

To assess the observed prevalence per year of takotsubo cardiomyopathy in a large registry of patients with STEMI, during a 12-year inclusion period.

Method

All patients presenting with STEMI at a large regional cardiology clinic were entered into a database (n = 8,413, mean age 63 ± 13 years). Takotsubo cardiomyopathy was diagnosed in 42 patients (0.5?%). Years of evaluation were defined as ‘early years’ (January 2002 to December 2007; n = 4350) and ‘later years’ (January 2008 to December 2013). Multivariable analyses were performed to adjust for differences in demographical and clinical variables.

Results

In later years, the age of STEMI patients was slightly higher (64 ± 13 vs. 63 ± 13 years, p < 0.001), with more patients with clinical symptoms of shock (10 vs. 7?%, p < 0.001) or a history of percutaneous coronary intervention or hypertension (10 vs. 8?%, p = 0.001 and 37 vs. 34?%, p < 0.001). Smoking and a positive family history were less often observed during later years (39 vs. 46?%, p < 0.001 and 37 vs. 42?% p < 0.001). Patients with takotsubo cardiomyopathy were more often female (81 vs. 27?%, p = 0.001). Takotsubo cardiomyopathy was more often diagnosed in the later period (0.7 vs. 0.3?%, OR 2.4, 95?% CI 1.2–4.6, p = 0.009). The higher prevalence of takotsubo cardiomyopathy in recent years remained significant after adjustment for differences in patient characteristics (OR 2.1, 95?% CI 1.1–4.3).

Conclusion

Takotsubo cardiomyopathy is currently more often diagnosed in patients with STEMI compared with in earlier years. This is probably due to the increased scientific and clinical awareness among doctors, but the prevalence is still low.

     

Clinical and economic impact of the introduction of a nucleic acid amplification assay for <Emphasis Type="Italic">Clostridium difficile</Emphasis>

Background

The clinical outcomes and cost implications of a diagnostic shift from an EIA- to PCR-based assay for Clostridium difficile infection (CDI) have not been completely described in the literature.

Methods

The impact of the PCR-based assay on the incidence and duration of CDI therapy was compared to the EIA assay for patients with a negative CDI diagnostic result. Secondary clinical and economic outcomes were also evaluated. Independent predictors of receipt of antibiotic therapy were assessed via logistic regression.

Results

141 EIA and 140 PCR patients were included. Significantly more patients were started or continued on anti-CDI antibiotic therapy after a known negative assay result in the EIA group (26 patients vs. 8 patients, P = 0.002). Duration of antibiotic therapy after a known negative result was significantly shorter in the PCR group (1 vs. 4 days, P = 0.029) and a 23% reduction in the number of tests obtained per patient was observed (1.41 ± 0.86 vs. 1.82 ± 1.35, P = 0.007). The over fourfold difference in per-test cost of the EIA assay ($8.33 vs. $42.86, P < 0.0001) was offset by the overall medication costs required for the increased treatment in the EIA group ($546.60 vs. $188.96, P = 0.191). Utilization of the EIA-based CDI assay was associated with increased odds of CDI treatment after a negative test (aOR 4.71, 95% CI 1.93–11.46, P = 0.001).

Conclusion

The transition from an EIA to PCR-based assay for diagnosing CDI resulted in a significant decrease in the number of patients treated and the duration of treatment in response to a negative test result. This significant decrease in treatment resulted in decreased costs offsetting the utilization of a more expensive molecular test for patients with a negative CDI diagnostic result.

     

Increased riboflavin production by knockout of 6-phosphofructokinase I and blocking the Entner–Doudoroff pathway in <Emphasis Type="Italic">Escherichia coli</Emphasis>

Objectives

To construct an Escherichia coli strain capable of producing riboflavin with high titer and yield.

Results

A low copy number plasmid pLS01 containing a riboflavin operon under the control of a constitutive promoter was constructed and introduced into Escherichia coli MG1655. Subsequently, the pfkA, edd and ead genes were disrupted, and the resulting strain LS02T produced 667 mg riboflavin/l in MSY medium supplied with 10 g glucose/l in flask cultivation. In a fed-batch process, riboflavin production of the strain reached 10.4 g/l with a yield of 56.8 mg riboflavin/g glucose.

Conclusion

To our knowledge, this is the first report of engineered E. coli strains that can produce more than 10 g riboflavin/l in fed-batch cultivation, indicating that E. coli has potential for riboflavin production.

     

Contribution of direct electron transfer mechanisms to overall electron transfer in microbial fuel cells utilising <Emphasis Type="Italic">Shewanella oneidensis</Emphasis> as biocatalyst

Objectives

To investigate the contribution of direct electron transfer mechanisms to electricity production in microbial fuel cells by physically retaining Shewanella oneidensis cells close to or away from the anode electrode.

Results

A maximum power output of 114 ± 6 mWm^?2 was obtained when cells were retained close to the anode using a dialysis membrane. This was 3.5 times more than when the cells were separated away from the anode. Without the membrane the maximum power output was 129 ± 6 mWm^?2. The direct mechanisms of electron transfer contributed significantly to overall electron transfer from S. oneidensis to electrodes, a result that was corroborated by another experiment where S. oneidensis cells were entrapped in alginate gels.

Conclusion

S. oneidensis transfers electrons primarily by direct electron transfer as opposed to mediated electron transfer.

     

<Emphasis Type="Italic">Streptococcus pyogenes</Emphasis>-purpura fulminans as an invasive form of group A streptococcal infection

Background

Streptococcus pyogenes is an uncommon pathogen of purpura fulminans, and the pathogenesis of S. pyogenes-purpura fulminans remains unclear because of paucity of cases. We reported a pediatric case of S. pyogenes-purpura fulminans with literature review of the disease.

Case presentation

A 3-year-old boy showed limping, lethargy and acral gangrene within 24 h. A diagnosis of S. pyogenes-purpura fulminans was made for bacterial isolation from throat and peripheral blood. Intensive therapy led to a survival with amputation of the left distal metatarsal bone, and normal development. The isolated M12 carried no mutation of csrS/R or rgg. Thrombophilia or immunodeficiency was excluded.

Discussion

Twelve-reported cases (9 pediatric and 3 elderly) of S. pyogenes-purpura fulminans started with shock and coagulopathy. Five patients age <?8 years had no underlying disease and survived. One youngest and two immunocompromised patients died.

Conclusion

Streptococcus pyogenes-acute infectious purpura fulminans is a distinctive rare form of aggressive GAS infections.

     

A prospective observational cohort study in primary care practices to identify factors associated with treatment failure in <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> skin and soft tissue infections

Background

The incidence of outpatient visits for skin and soft tissue infections (SSTIs) has substantially increased over the last decade. The emergence of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has made the management of S. aureus SSTIs complex and challenging. The objective of this study was to identify risk factors contributing to treatment failures associated with community-associated S. aureus skin and soft tissue infections SSTIs.

Methods

This was a prospective, observational study among 14 primary care clinics within the South Texas Ambulatory Research Network. The primary outcome was treatment failure within 90 days of the initial visit. Univariate associations between the explanatory variables and treatment failure were examined. A generalized linear mixed-effect model was developed to identify independent risk factors associated with treatment failure.

Results

Overall, 21% (22/106) patients with S. aureus SSTIs experienced treatment failure. The occurrence of treatment failure was similar among patients with methicillin-resistant S. aureus and those with methicillin-susceptible S. aureus SSTIs (19 vs. 24%; p = 0.70). Independent predictors of treatment failure among cases with S. aureus SSTIs was a duration of infection of ≥7 days prior to initial visit [aOR, 6.02 (95% CI 1.74–19.61)] and a lesion diameter size ≥5 cm [5.25 (1.58–17.20)].

Conclusions

Predictors for treatment failure included a duration of infection for ≥7 days prior to the initial visit and a wound diameter of ≥5 cm. A heightened awareness of these risk factors could help direct targeted interventions in high-risk populations.

     

Does centrifugation matter? Centrifugal force and spinning time alter the plasma metabolome

Background

Centrifugation is an indispensable procedure for plasma sample preparation, but applied conditions can vary between labs.

Aim

Determine whether routinely used plasma centrifugation protocols (1500×g 10 min; 3000×g 5 min) influence non-targeted metabolomic analyses.

Methods

Nuclear magnetic resonance spectroscopy (NMR) and High Resolution Mass Spectrometry (HRMS) data were evaluated with sparse partial least squares discriminant analyses and compared with cell count measurements.

Results

Besides significant differences in platelet count, we identified substantial alterations in NMR and HRMS data related to the different centrifugation protocols.

Conclusion

Already minor differences in plasma centrifugation can significantly influence metabolomic patterns and potentially bias metabolomics studies.

     

Degradation of carbazole,dibenzothiophene and polyaromatic hydrocarbons by recombinant <Emphasis Type="Italic">Rhodococcus</Emphasis> sp.

Objectives

With the view of designing a single biocatalyst for biorefining, carbazole dioxygenase was cloned from Pseudomonas sp. and expressed in Rhodococcus sp.

Results

The recombinant, IGTS8, degraded both carbazole and dibenzothiophene at 400 mg/l in 24 h. Maximum carbazole degradation was in 1:1 (v/v) hexadecane/aqueous phase. Anthracene, phenanthrene, pyrene, fluoranthene and fluorine were also degraded without affecting the aliphatic component.

Conclusions

Recombinant Rhodococcus sp. IGTS8 can function as a single biocatalyst for removing major contaminants of fossil fuels viz. dibenzothiophene, carbazole and polyaromatic compounds.

     

Expression of a high sweetness and heat-resistant mutant of sweet-tasting protein,monellin, in <Emphasis Type="Italic">Pichia pastoris</Emphasis> with a constitutive GAPDH promoter and modified <Emphasis Type="Italic">N</Emphasis>-terminus

Objectives

To improve the stability and sweetness of the sweet-tasting protein, monellin, by using site-directed mutagenesis and a Pichia pastoris expression system with a GAPDH constitutive promoter.

Results

Both wild-type and E2 N mutant of single-chain monellin gene were cloned into the PGAPZαA vector and expressed in Pichia pastoris. The majority of the secreted recombinant protein, at 0.15 g/l supernatant, was monellin. This was purified by Sephadex G50 chromatography. The sweetness threshold of wild-type and E2 N were 30 μg/ml and 20 μg/ml, respectively. Compared with the proteins expressed in Escherichia coli, the thermostability of both proteins was improved. The N-terminal sequence is determinative for the sweetness of the proteins expressed in yeast strains.

Conclusions

Site-directed mutagenesis, modification of the N-terminus of monellin, and without the need of methanol induction in P. pastoris expression system, indicate the possibility for large-scale production of this sweet-tasting protein.