[Etiological characterization of invasive non-typhoid Salmonella strains in Guangdong Province from 2018 to 2022].

Objective: To understand the serotype distribution, drug resistance and molecular characterization of invasive non-typhoid Salmonella (iNTS) in Guangdong Province from 2018 to 2022 and provide scientific evidence for the prevention and treatment of blood flow infection caused by Salmonella. Methods: Serological identification, antimicrobial susceptibility testing, multilocus sequence typing (MLST), and whole genome sequencing were performed on Salmonella isolated from blood and stool samples in Guangdong from 2018 to 2022. Simultaneously, annotated the sequencing results for drug resistance genes and virulence factors by a microbial gene annotation system. Results: The 136 iNTS strains were divided into 25 serotypes, and Salmonella enteritidis accounted for 38.24% (52/136). The OR of other iNTS serotypes were calculated with Salmonella typhimurium as the control. The OR values of Oreninburg, Rysson, and Pomona serotypes were the highest, which were 423.50, 352.92, and 211.75, respectively. The drug resistance rate of iNTS was 0.74%-66.91%, which was lower than that of non-iNTS (3.90%-77.21%). The main iNTS of drug resistance were ampicillin and tetracycline, with resistance rates of 66.91% (91/136) and 50.00% (68/136), respectively, while the resistance rates to ciprofloxacin (5.88%,8/136), ceftazidime (5.88%,8/136), gentamicin (5.13%,7/136) and cefoxitin (0.74%, 1/136) were relatively low. iNTS carried a variety of drug-resistance genes and virulence factors, but no standard virulence factor distribution has been found. MLST cluster analysis showed that iNTS was divided into 26 sequence types, and ST11 accounted for 38.24% (52/136). Conclusions: The iNTS strains in Guangdong were dominated by Salmonella enteritidis, of which three serotypes, Oreninburg, Rison, and Pomona, may be associated with a higher risk of invasive infection during 2018 to 2022. iNTS was sensitive to clinical first-line therapeutic drugs (cephalosporins and fluoroquinolones), with highly diverse sequences and clear phylogenetic branches. ST11 was the local dominant clone group.

Diagnosis of spinal dural arteriovenous fistula: a multimodal MRI assessment strategy.

AIM: To identify more specific screening indicators at magnetic resonance imaging (MRI) for the diagnosis of spinal dural arteriovenous fistulas (SDAVFs) and to determine an efficient diagnostic strategy. MATERIALS AND METHODS: This retrospective study analysed clinical and imaging data of patients diagnosed with SDAVF and alternative myelopathy who underwent conventional MRI examinations. Additionally, three-dimensional (3D) T2-weighted sampling perfection with application-optimised contrasts using different flip-angle evolutions (3D-T2-SPACE) and contrast-enhanced magnetic resonance angiography (CE-MRA) data from patients with SDAVF were compared with digital subtraction angiography (DSA) data. RESULTS: The age of onset, perimedullary flow voids (PFV), distribution of lesions, syringomyelia, degree of spinal oedema, and cauda equina disorder (CED) were factors that showed statistically significance in the identification of SDAVF with alternative myelopathy. After controlling for age, gender, PFV, degree of spinal cord swelling, and syringomyelia, the multivariable ordinal logistic regression model showed that the CED sign (OR = 32.46; 95% confidence interval [CI]: 2.47-427.15; p=0.008) was an independent predictor for SDAVF. The diagnostic model constructed using the PFV and CED signs had better diagnostic performance, with an area under the curve of 0.957 (p<0.001), maximum Youden index of 0.844, sensitivity of 92.9%, and specificity of 91.5%. Both 3D-T2-SPACE (77.8%) and CE-MRA (83.3%) sequences had good localisation values for SDAVF. Combining the two imaging examinations had better diagnostic accuracy than that of DSA. CONCLUSION: CED and PFV on conventional MRI were specific indicators for the diagnosis of SDAVF. To compensate for the lack of fistula localisation on conventional MRI, 3D-T2-SPACE and CE-MRA can be used. Together they complement each other and have good diagnostic potential.

Global taxonomic, functional, and phylogenetic diversity of bees in apple orchards.

An essential prerequisite to safeguard pollinator species is characterisation of the multifaceted diversity of crop pollinators and identification of the drivers of pollinator community changes across biogeographical gradients. The extent to which intensive agriculture is associated with the homogenisation of biological communities at large spatial scales remains poorly understood. In this study, we investigated diversity drivers for 644 bee species/morphospecies in 177 commercial apple orchards across 33 countries and four global biogeographical biomes. Our findings reveal significant taxonomic dissimilarity among biogeographical zones. Interestingly, despite this dissimilarity, species from different zones share similar higher-level phylogenetic groups and similar ecological and behavioural traits (i.e. functional traits), likely due to habitat filtering caused by perennial monoculture systems managed intensively for crop production. Honey bee species dominated orchard communities, while other managed/manageable and wild species were collected in lower numbers. Moreover, the presence of herbaceous, uncultivated open areas and organic management practices were associated with increased wild bee diversity. Overall, our study sheds light on the importance of large-scale analyses contributing to the emerging fields of functional and phylogenetic diversity, which can be related to ecosystem function to promote biodiversity as a key asset in agroecosystems in the face of global change pressures.

Fetal vitamin D concentration and growth, adiposity and neurodevelopment during infancy.

BACKGROUND/OBJECTIVES: To determine the association between cord blood 25-hydroxyvitamin D (25(OH)D) concentration with growth, adiposity and neurodevelopment during infancy. SUBJECTS/METHODS: Serum 25(OH)D was measured in cord blood by the liquid chromatography tandem mass spectrometry (LC-MS/MS) from the Shanghai's "Allergy and Obesity Cohort study" (n = 1244). Weight, length, head circumference, and body mass index (BMI) z-scores for age were calculated based on World Health Organization Standard (at 6 months, 1 years, and 2 years). Neurodevelopment was measured at 2 years using Ages and Stages Questionnaire. Generalized estimating equation and multivariable logistic regression model were exploited to examine associations between fetal 25(OH)D concentration and offspring outcomes. RESULTS: The median of the 25(OH)D concentration in cord blood was 22.4 ng/ml (interquartile range, 27.3-8.6). Infants born in winter had lower 25(OH)D concentration. 25(OH)D deficiency was not associated with weight z-score (mean difference, 0.07; 95% confidence internal (CI), -0.09 to 0.23), length z-score (mean difference, 0.01; 95% CI, -0.19 to 0.21), head circumference z-score (mean difference, -0.06; 95% CI, -0.27 to 0.15) and BMI z-score (mean difference, 0.09; 95% CI, -0.07 to 0.25) or neurodevelopment during infancy, adjusting for sex, socio-economic position, pre-pregnancy maternal BMI, and maternal and neonatal characteristics. The associations did not vary by gender. A sensitivity analysis of available case analysis showed virtually the same results. CONCLUSIONS: Fetal vitamin D concentration was not associated with growth, adiposity or neurodevelopment during infancy. The role of vitamin D concentration and its mechanistic pathway in the early origins of adiposity needs to be clarified.

Value of two-cycle docetaxel, cisplatin, and 5-fluorouracil induction chemotherapy in hypopharyngeal carcinoma.

Various studies have investigated laryngeal function and survival after induction chemotherapy in hypopharyngeal carcinoma, but potential factors to help predict response rates after induction chemotherapy remain unknown. This retro- spective study evaluated which factors are related to an ineffective response to two-cycle docetaxel, cisplatin, and 5-fluoro- uracil (TPF) induction chemotherapy in hypopharyngeal carcinoma to determine potential candidates for this treatment in clinical practice. From Jan 2005 to Dec 2015, 81 patients diagnosed with hypopharyngeal squamous cell carcinoma based on a pathological examination were analyzed. They were administered two-cycle TPF induction chemotherapy, and magnetic resonance imaging was performed before and after induction chemotherapy. The mean survival time was 5.7 years (95% confidence interval, 5.1-6.2 years). The 1, 3, 5 and 6-year survival rates were 98.8%, 80.1%, 64.5%, and 54.2%, respectively. TPF induction chemotherapy was well tolerated; the main adverse effects resolved with symptomatic treatment. A response to TPF induction chemotherapy was associated with lymph node size, tumor grade, invasion region, T stage, and primary tumor. The following issues were significantly associated with an increasing non-response rate to two-cycle induction chemotherapy: increasing lymph node size, moderately differentiated squamous cell carcinoma, invasion of the esophagus along with the thyroid cartilage, and primary tumor in the piriform sinus. Lymph nodes of ≥2.15 cm, moderately differenti- ated tumor grade, or thyroid cartilage invasion were the best cutoff values for patients who did not respond to induction chemotherapy. However, the initial cancer site, cancer stage, and degree of cancer differentiation were not closely related to the efficacy of induction chemotherapy.

[Predictive value of cardiac magnetic resonance-derived parameters on the improvement of left ventricular function in patients with acute viral myocarditis].

Objective: To evaluate the predictive value of cardiac magnetic resonance (CMR)-derived parameters on the improvement of left ventricular function in patients with acute viral myocarditis. Methods: Forty patients, who referred for acute viral myocarditis in our hospital from September 2011 to September 2015, were prospectively enrolled in this study.All patients were examined by CMR during hospitalization for acute viral myocarditis (baseline) and after 12 months.The CMR sequences include: two dimension steady state free precession, 2D SSFP; triple inversion recovery, triple IR; early gadolinium enhancement; phase sensitive inversion recovery turbo field echo, PSIR TFE. Results: Thirty out of 40 patients with susceptive acute viral myocarditis met the CMR criteria of acute viral myocarditis (Lake Louise Criteria) (LL+ ) and the other 10 patients did not meet the diagnostic criteria (LL-). Left ventricular ejection fraction (LVEF) values were significantly lower in LL+ group than in LL- group at baseline and at 12 months after discharge (P<0.01 or 0.05, respectively). The baseline left ventricular end-systolic volume index (LVESVI) was significantly higher in LL+ group than in LL- group (P<0.05) and was similar between the groups at 12 months follow up.Left ventricular end-diastolic volume index (LVEDVI )was similar between the two groups at baseline and at 12 months follow up.LVEF was significantly higher during 12 months follow up compared to baseline in LL+ group and remained unchanged in LL- group during the two time points.LVESVI and LVEDVI remained unchanged at baseline and during 12 months follow up both in LL+ and LL- groups (P>0.05). Results showed that LL+ , edema ratio (ER) positive and global relative enhancement (gRE) positive were associated with significant increase of LVEF at 12 months follow up.However, LL-, ER negative, gRE negative, late gadolinium enhancement(LGE) negative and LGE positive linked with unchanged LVEF at 12 months follow up (P>0.05). Patients were further divided into LVEF increase (ΔLVEF≥5%) group and non LVEF increase group (ΔLVEF<5%), the results of Chi-square test showed that LL+ and ER positive were related to the improvement of LVEF (P<0.05), while gRE and LGE were not associated with improvement of cardiac function (P>0.05). Multiple linear regression analysis, using ER, gRE and LGE as independent variables and LVEF as dependent variables, showed that the presence of myocardial edema was the strongest independent predictor of an increase in LVEF at follow up (full model: non-standardized coefficient 0.445, P=0.043; reduced model: non-standardized coefficient 0.442, P=0.12). Conclusion: Cardiac magnetic resonance imaging monitoring is valuable to observe the cardiac function and morphology changes in patients with acute viral myocarditis, and myocardial edema imaging is the most powerful parameter to predict the improvement of LVEF in this patient cohort.

[Pulmonary vein isolation for atrial fibrillation : Findings from long-term follow-up]. / Pulmonalvenenisolation bei Vorhofflimmern : Erkenntnisse aus klinischen Langzeitdaten.

Atrial fibrillation is by far the most common cardiac arrhythmia in humans. The incidence of atrial fibrillation increases with age and will increase even more in the future due to the demographic changes in the population. Therefore, this arrhythmia will have a growing clinical and socioeconomic impact. Although there are established pharmaceutical treatment options, atrial fibrillation is one of the major causes of stroke, heart failure and cardiovascular morbidity and mortality. The latest guidelines recommend the invasive procedure of circumferential pulmonary vein isolation (PVI) as an effective treatment of paroxysmal and persistent atrial fibrillation. This article summarizes the current long-term follow-up data after PVI.

[Innovative techniques in atrial fibrillation therapy]. / Innovative Verfahren der Vorhofflimmertherapie.

Pulmonary vein isolation (PVI) is the established cornerstone in most catheter-based ablation treatment strategies for atrial fibrillation (AF); however, it is still a challenge to create contiguous, transmural and permanent ablation lesions using radiofrequency current in combination with three-dimensional mapping systems. To overcome these limitations, innovative spiral mapping and ablation catheters as well as balloon-based ablation catheters incorporating alternative energy sources, such as cryoenergy and laser were developed and evaluated and have proved their potential for safe and clinically effective PVI. In addition, novel ablation strategies, such as identification and ablation of AF-inducing foci and/or AF-perpetuating rotors using either endocardial or epicardial mapping systems were introduced and are currently under clinical evaluation. The identification and modulation of atrial ganglionic plexi (GP) and, therefore, of the autonomous nervous system is another additive ablation approach which requires further clinical evaluation.

[Syncope : epidemiology, definition, classification, pathophysiology and prognosis]. / Synkope : Epidemiologie, Definition, Klassifikation, Pathophysiologie und Prognose.

Syncope is a common clinical issue. Around 40 % of the total population experience syncope during their lifetime. Serious injuries and reduced quality of life are often observed after syncope. Furthermore, in some cases syncope can be associated with an unfavorable prognosis. Due to the complex etiology and pathophysiology, syncope provides challenges for doctors both in private and in clinical practices. This review is based on the latest European guidelines for syncope which were formulated by internists, neurologists, emergency physicians and cardiologists and gives an overview of the current epidemiology, definition, classification, pathophysiology and prognosis of syncope.

Trends in overweight and obesity among rural preschool children in southeast China from 1998 to 2005.

OBJECTIVE: To examine the trends in prevalence of overweight and obesity, as well as the impact of stunting on overweight/obesity, among rural children aged <60 months in southeast China between 1998 and 2005. STUDY DESIGN: Data from the population-based Child Health Care Surveillance System (CHCSS) from eight counties in southeast China were used. Overweight and obesity were defined as weight-for-height/length z score >2 and >3 standard deviations (SDs), respectively, and stunting was defined as height/length-for-age z score <-2 SD, in accordance with the 2006 World Health Organization growth standard. METHODS: A total of 550,693 clinic visit records of 280,931 children from the CHCSS, collected between 1998 and 2005, were included in the analysis. The age- and sex-adjusted prevalence rates of overweight, obesity and stunting were estimated for each year, and the trends over time were examined. The impact of stunting on overweight/obesity was determined using multiple logistic regression analysis. RESULTS: The prevalence of overweight increased from 3.7% in 1998 to 3.9% in 2005 (P < 0.001), but no increase in the prevalence of obesity was observed (0.5% in 1998 and 0.6% in 2005; P > 0.05). The prevalence of obesity increased significantly in 2005 compared with 1998 among boys aged ≥24 months, but was similar between 1998 and 2005 for girls aged ≥12 months. The prevalence of stunting decreased from 3.9% in 1998 to 1.6% in 2005 (P < 0.001). There was a positive association between stunting and overweight/obesity in both 1998 and 2005, although the association was attenuated in 2005. CONCLUSION: There was a small increase in the prevalence of overweight among rural preschool children in southeast China from 1998 to 2005. The prevalence of obesity remained stable. However, the prevalence of stunting decreased and its positive influence on overweight/obesity was weaker in 2005.

Distant metastasis in triple-negative breast cancer.

Triple-negative breast cancer (TNBC) relapses more frequently than hormone receptor-positive subtypes and is often associated with poor outcomes. This retrospective study reviewed the pattern of distant metastasis with regard to survival in patients with TNBC. A total of 205 TNBC patients were analyzed. TNBC patients with lung metastases had the longest median post-metastatic OS (with 95% confidence interval) of 16.6 (10.3-22.9) months, followed by the bone, 16.3 (11.7-20.8) months, the liver, 8.9 (3.5-14.4) months, the pleura, 7.5 (2.8-12.3) months, and the brain, 4.3 (0.6-8.0) months. Kaplan-Meier plots indicated that TNBC patients with metastatic spread to brain, liver, and pleural had poorer post-metastatic OS rate than patients with lung metastases (p = 0.001, 0.004, and 0.029, respectively). Moreover, brain and liver metastases correlated significantly with poorer post-metastatic OS as compared to bone metastasis (p = 0.004 and 0.011, respectively). Route of first metastasis correlated significantly with survival of TNBC patients with brain metastases being the poorest survival indicator, followed by metastases to liver, pleura, bone, and lung.

Association between short sleep duration and the risk of sensitization to food and aero allergens in rural Chinese adolescents.

BACKGROUND: Both long and short sleep duration have been associated with obesity, cardiovascular disease, and diabetes. However, there have been no previous studies investigating the potential relationship between altered sleep duration and allergen sensitization. OBJECTIVE: To explore the association between sleep duration and sensitization to food and aeroallergens. METHODS: This study includes 1534 rural Chinese adolescent twins aged 12-21 years who completed standard sleep questionnaires and skin prick tests (SPTs) to nine food and five aeroallergens. Total sleep time was defined as the interval from bedtime to wake-up time minus sleep latency. Sensitization was defined as having at least one positive SPT. RESULTS: Compared with individuals with the highest (third) tertile of sleep duration, those who slept less were more likely to be sensitized to any food allergen with odds ratios (ORs) of 1.9 [95% confidence interval (CI): 1.3-2.7] and 1.4 (95% CI: 1.0-1.9) for the first and second tertiles (trend test P(trend)=3×10(-4)), respectively. The corresponding ORs for sensitization to any aeroallergen were 1.5 (95% CI: 1.1-2.0) and 1.3 (95% CI: 1.0-1.7) (P(trend)=8×10(-3)). These associations were independent of percent body fat. In addition, we observed a significant dose-response association between the number of positive SPTs and percentage of shortest sleep duration (first tertile) (P(trend)=1×10(-3)). CONCLUSIONS AND CLINICAL RELEVANCE: In this sample of relatively lean rural Chinese adolescents, we found that short sleep duration was associated with increasing risk of sensitization to food and aeroallergens, independent of percent body fat. Longitudinal studies are needed to further determine the temporal and causal relationships. If short sleep duration indeed is one of the risk factors for allergic sensitization, the global burden of allergic diseases could be dramatically reduced by providing appropriate guidance on sleep duration for youth.

Cord blood immune biomarkers in small for gestational age births.

Fetal growth restriction is a risk factor for development of adulthood diseases, but the biological mechanism of this association remains unknown. Limited biomarkers have been studied in settings of preterm birth and maternal inflammation, but the relationship between a wide range of immune biomarkers and fetal growth has not been studied. The hypothesis of this study was that fetal growth restriction is associated with altered immune biomarker levels. We examined the relationship between small for gestational age (SGA) status and 27 umbilical cord blood immune biomarkers. This study was part of a large-scale cohort study of preterm birth and low birth weight conducted at Boston Medical Center, an inner city, predominantly minority patient population. Growth status was determined based on birth weight standardized to an internal reference. There were 74 SGA births and 319 appropriate for age (AGA) births with complete clinical and biomarker data. Adjusting for covariates and using AGA as reference, SGA births had lower levels of log IL-1ß (ng/l; ß -0.38, 95% CI -0.57, -0.19, P < 0.01), log BDNF (ß -0.29, 95% CI -0.55, -0.03, P < 0.05) and log NT-3 (ß -0.46, 95% CI -0.77, -0.15, P < 0.01). No associations were found between other biomarkers and SGA. In conclusion, three biomarkers were selectively associated with SGA status. Our results provide information that could be used to guide additional studied aimed at determining mechanisms that contribute to fetal growth.

Menstrual cycle lengths and bone mineral density: a cross-sectional, population-based study in rural Chinese women ages 30-49 years.

INTRODUCTION: The menstrual cycle involves periodic fluctuations in estrogen and progesterone levels. Longer cycles have been associated with longer follicular phase, delayed estrogen peak and a lower mean oestradiol level of the entire cycle. METHODS: We hypothesized that prolonged menstrual cycle length is associated with decreased bone mineral density (BMD) in a population of pre- and perimenopausal women. This population-based cross-sectional study was conducted in rural Anhui province, China. It includes 4,771 women, aged 30 to 49 years, who did not smoke or drink alcohol, and did not use oral contraceptives or breastfeed during the previous year. Dual-energy X-ray absorptionometry (DEXA) BMD measurements were taken at four skeletal sites: whole body, total hip, femoral neck and lumbar spine. Menstrual cycle characteristics (polymenorrhea, short normal, long normal, oligomenorrhea, 90-day amenorrhea, irregular cycle) in the prior year were assessed by questionnaire. RESULTS: Prolonged menstrual cycle was consistently associated with decreased BMD at whole body, total hip, and femoral neck in both age 30-39, and age 40-49 stratum (p(trend)<0.05). Prolonged menstrual cycle was also associated with decreased lumbar spine BMD for women aged 40-49 (p(trend)<0.05). Among women with normal cycles aged 30-39, menstrual cycle length in the previous year was inversely associated with whole-body BMD (p<0.05). Women with 90-day amenorrhea had significantly lower mean total hip and femoral neck BMD relative to women with short normal cycles in the 30-39 age group; and had significantly lower whole body and total hip BMD relative to short normal cycles in the 40-49 age group. BMD in polymenorrheic women did not differ from BMD in women with short normal cycles at any of the skeletal sites. CONCLUSIONS: We conclude that prolonged menstrual cycle length is associated with decreased BMD in pre- and perimenopausal women in this population.

Serum DDT, age at menarche, and abnormal menstrual cycle length.

BACKGROUND: Although dichlorodiphenyl trichloroethane (DDT) exposure is known to affect human endocrine function, few previous studies have investigated the effects of DDT exposure on age at menarche or menstrual cycle length. METHODS: A cross sectional study was conducted to study the effects of DDT exposure on age at menarche and menstrual cycle length among 466 newly married, nulliparous female Chinese textile workers aged 20-34 years enrolled between 1996 and 1998. Serum was analysed for DDT and its major metabolites. Multivariate linear regression was used to estimate DDT exposure effects on age at menarche and multivariate logistic regression was used to estimate DDT exposure effects on odds of experiencing short or long cycles. RESULTS: Relative to those in the lowest DDT quartile, the adjusted mean age at menarche was younger in those in the fourth quartile (-1.11 years). Modeled as a continuous variable, a 10 ng/g increase in serum DDT concentration was associated with an adjusted reduction in age at menarche of 0.20 years. Relative to those in the lowest DDT quartile, odds of any short cycle (<21 days) in the previous year were higher for those in the fourth quartile (odds ratio = 2.78; 95% CI 1.07 to 7.14). There were no associations between serum DDT concentrations and odds of experiencing a long cycle (>40 days). CONCLUSION: Results suggest that DDT exposure was associated with earlier age at menarche and increased risk of experiencing a shortened menstrual cycle.

Regulation of CO on heterocyst differentiation and nitrate uptake in the cyanobacterium Anabaena sp. PCC 7120.

AIMS: The aim of the present investigation was to study the effects of different inorganic carbon and nitrogen sources on nitrate uptake and heterocyst differentiation in the culture of cyanobacterium Anabaena sp. PCC 7120. METHODS AND RESULTS: Anabaena was cultivated in media BG11 containing combined nitrogen and supplementary NaHCO3 or CO2. Cell growth, heterocyst differentiation, nitrate reductase (NR, EC 1.7.7.2), glucose-6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49) and NO uptake were analysed. The cells cultivated in BG11(0) medium with aeration were taken as reference. Experimental results showed that the differentiation frequency of heterocysts when the cells were cultivated with elevated CO2 was higher than that of the cells grown with air or bicarbonate. Heterocysts appeared unexpectedly when CO2 was introduced into the medium containing nitrate. However, no heterocysts emerged when CO2 was added to medium containing NH or urea, or when NaHCO3 was supplied to the medium with nitrate. Both nitrate uptake rate and nitrate reduction enzyme activity were depressed by the supplement of CO2 to the culture. The activity of G6PDH was enhanced with the increase in heterocyst differentiation frequency. CONCLUSION: CO2 might compete with NO for energy and electrons in the uptake process and CO2 appears favoured. This led to a high intracellular C/N ratio and a relative N limitation. So the process of heterocyst differentiation was activated to supplement nitrogen uptake. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provided an attractive possibility to form more heterocysts by rapid growth of Anabaena cells cultivated in the medium containing nitrate in order to increase nitrogen fixation and hydrogen production.

[Studies on the growth characteristics of Spirulina cells under batch and continuous conditions].

The research paper focused mainly on the growth characteristics of Spirulina cells under batch and continuous conditions. It was found that the Richards and Exponential decay model could well express the relationships between the concentration of the cell, carbon in the medium and culture time respectively. The maximum cell growth rate and the cell yield coefficient against carbon under batch culture was 0.371 g/d/L and 3.439 g/gC respectively. The concentration of cell and that of carbon in the reactor increased and decreased with the dilution rate respectively under the continuous culture condition. The maximum cell growth rate and the optimum dilution rate was 0.362 g/d/L and 0.45/d respectively. The cell yield against carbon under continuous culture condition was 2.050 g/gC. The cell growth rate of batch culture was larger than that of continuous one when the cell concentration was relatively low, but it will be smaller than that of continuous culture when the cell concentration became high.

[Culture medium optimization and primary kinetics analysis for nisin production].

Response surface methodology was used to optimize a medium for nisin production of Lactococcus lactis. In the first optimization step the influence of sucrose, soybean peptone, yeast extract, potassium dihydrogen phosphate, sodium chloride, and magnesium sulfur on nisin production was evaluated using a fractional factorial design. Potassium dihydrogen phosphate influenced nisin production positively while soybean peptone affected nisin production negatively. The other components had no significant effect on nisin production. The path of steepest ascent was used to approach the optimal region of the medium composition. In the third step the optimal concentrations of KH2PO4 and soybean peptone were determined by a central composite design and response surface analysis. The optimized medium allowed nisin production to be increased from 1074 IU/mL to 2150 IU/mL. The kinetic analysis showed that nisin production fashion at optimized and non-optimized media was not changed and maintained partially growth-associated. But the specific growth rates and the specific nisin production rates for the strain at the optimized medium were bigger than the ones at the non-optimized medium after the cells entered the middle of exponential phase.

Optimization of conditions for bacteriocin extraction in PEG/salt aqueous two-phase systems using statistical experimental designs.

The bacteriocin nisin was extracted in PEG/salt aqueous two-phase systems (ATPS) using the property that the systems can extract hydrophobic proteins. The concentrations of the phase-forming components, PEG 4000 and Na(2)SO(4), were optimized for nisin recovery by means of statistical experimental designs, and it was found that they strongly influenced nisin recovery. The optimal composition of ATPS was found to be 15.99% (w/w) PEG 4000 and 15.85% (w/w) Na(2)SO(4) (pH 2), and the optimal ATPS allowed an 11.60% increase of nisin recovery compared to the standard method of nisin assay.