A metabolic model of Lipomyces starkeyi for predicting lipogenesis potential from diverse low-cost substrates.

BACKGROUND: Lipomyces starkeyi has been widely regarded as a promising oleaginous yeast with broad industrial application prospects because of its wide substrate spectrum, good adaption to fermentation inhibitors, excellent fatty acid composition for high-quality biodiesel, and negligible lipid remobilization. However, the currently low experimental lipid yield of L. starkeyi prohibits its commercial success. Metabolic model is extremely valuable to comprehend the complex biochemical processes and provide great guidance for strain modification to facilitate the lipid biosynthesis. RESULTS: A small-scale metabolic model of L. starkeyi NRRL Y-11557 was constructed based on the genome annotation information. The theoretical lipid yields of glucose, cellobiose, xylose, glycerol, and acetic acid were calculated according to the flux balance analysis (FBA). The optimal flux distribution of the lipid synthesis showed that pentose phosphate pathway (PPP) independently met the necessity of NADPH for lipid synthesis, resulting in the relatively low lipid yields. Several targets (NADP-dependent oxidoreductases) beneficial for oleaginicity of L. starkeyi with significantly higher theoretical lipid yields were compared and elucidated. The combined utilization of acetic acid and other carbon sources and a hypothetical reverse ß-oxidation (RBO) pathway showed outstanding potential for improving the theoretical lipid yield. CONCLUSIONS: The lipid biosynthesis potential of L. starkeyi can be significantly improved through appropriate modification of metabolic network, as well as combined utilization of carbon sources according to the metabolic model. The prediction and analysis provide valuable guidance to improve lipid production from various low-cost substrates.

Efficient conversion of chitin-derived carbon sources into microbial lipid by the oleaginous yeast Cutaneotrichosporon oleaginosum.

Chitin represents the second most abundant biomass after lignocelluloses in the biosphere. It can be depolymerized into either N-acetylglucosamine (GlcNAc) or glucosamine (GlcN) and acetate by different degradation strategies. However, these chitin-derived carbon sources have been scarcely compared for lipid production. Here, GlcNAc was found superior to GlcN or acetate for lipid accumulation by Cutaneotrichosporon oleaginosum. The lipid accumulation potential of these carbon sources was calculated based on a small scale metabolic model of C. oleaginosum. Co-fermentation of GlcN and acetate under phosphate limitation rendered improved lipid production. GlcN and acetate were assimilated simultaneously. The highest lipid titer and yield of 10.1 g/L and 0.25 g/g, respectively, was reached when GlcNAc was used under phosphate limitation. The fatty acids composition of the lipid samples showed similarities to vegetable oils, demonstrating the suitability in biodiesel industry. This study provides profitable guidance for the design of chitin-to-lipids routes.

Deficiency of ß-Glucosidase Beneficial for the Simultaneous Saccharification and Lipid Production by the Oleaginous Yeast Lipomyces starkeyi.

It is inevitably for cellobiose to be co-generated during enzymatic hydrolysis of cellulose, especially when the cellulase is lack of ß-glucosidase activity. In the present study, cellobiose was found superior to glucose for cell growth by L. starkeyi, regardless of the sugar concentrations. Glucose was assimilated preferentially when cellobiose and glucose were co-fermented. Deficiency of ß-glucosidase was observed to be beneficial for the simultaneous saccharification and lipid production (SSLP). High lipid titer and cellulose conversion of 9.1 g/L and 92.4%, respectively, were achieved when cellulase with low ß-glucosidase activity was supplemented. The SSLP achieved higher lipid titer of 9.5 g/L when a pre-hydrolysis process was introduced. The glucosidase generated by L. starkeyi was primarily cell-bound, which contributed significantly to the cellobiose utilization and the high lipid production. These results provided a novel scheme for enhanced lipid production from lignocellulosic biomass with reduced enzyme usage, which is believed to facilitate the design of a more cost-effective lignocellulose-to-lipid route.

Phosphate removal combined with acetate supplementation enhances lipid production from water hyacinth by Cutaneotrichosporon oleaginosum.

BACKGROUND: Microbial lipids derived from various lignocellulosic feedstocks have emerged as a promising candidate for the biodiesel industry and a potential substitute for high value-added fats. However, lignocellulosic biomass, especially herbaceous biomass, such as water hyacinth, contains high concentrations of nitrogenous components. These compounds impede microbial lipid production, as lipid biosynthesis is commonly induced by imposing a nutrient deficiency, especially nitrogen starvation. Novel strategies and bioprocesses are pivotal for promoting lipid production from nitrogen-rich biomass. RESULTS: Here a combined strategy of phosphate removal and acetate supplementation was described for enhanced microbial lipid production on water hyacinth hydrolysates by Cutaneotrichosporon oleaginosum (formerly Cryptococcus curvatus). Lipid production was significantly improved, when the phosphorus limitation and sugars/acetate co-utilization strategies were used separately. In this case, acetate and glucose were consumed simultaneously. Lipid production was observed by the combination of phosphate removal with acetate supplementation. Lipid titer, content, and yield were determined to be 7.3 g/L, 59.7% and 10.1 g/100 g raw water hyacinth, respectively. These data were increased by 4.2, 4.6, and 4.3 times, respectively, compared to those from the unprocessed hydrolysates. The fatty acid compositions of the resulting lipids bear a marked resemblance to those of rapeseed oil, indicating their applicability to the biodiesel industry. CONCLUSIONS: The combination of phosphate removal and acetate supplementation was successful in significantly enhancing microbial lipid production. This strategy offers a valuable solution for nitrogen-rich lignocellulosic feedstocks utilization, which should foster more economical nitrogen-rich biomass-to-lipid bioprocesses.

Efficacy of cognitive behavioural therapy with medication for patients with obsessive-compulsive disorder: A multicentre randomised controlled trial in China.

BACKGROUND: Meta-analyses support the efficacy of cognitive behavioural therapy (CBT) for obsessive-compulsive disorder (OCD) in Western cultures. However, there are no adequately powered multicentre studies in China. This study aimed to compare the effectiveness of treatment with CBT combined with medication and medication alone in OCD patients in China. METHODS: OCD patients (N = 167) were recruited from outpatient clinics at three large tertiary psychiatric hospitals and one general hospital in China. Participants were randomly allocated to receive either CBT combined with medication (n = 92) or medication alone (n = 75) for a 24-week treatment period. Participants' symptoms and social functioning were assessed using the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS), Hamilton Anxiety Rating Scale (HAM-A), Global Assessment of Functioning (GAF) and Clinical Global Impression Scale for Severity (CGI-S) at 0, 4, 8, 12 and 24 weeks, and the effectiveness of the two treatments compared using linear mixed-effects models. RESULTS: At 24 weeks, both groups showed large within-group effects in all measures. Significantly more patients receiving combined therapy than medication alone had a decrease in symptom severity of at least 35% (based on Y-BOCS total score). The CGI-S and GAF scores decreased in both groups, and significant differences were found between the groups. LIMITATIONS: Study limitations included lack of consideration of medication types and dosages, and the absence of a CBT-only arm. CONCLUSIONS: CBT combined with medication may be effective in alleviating symptoms and social functioning impairment associated with OCD, and is more effective than medication alone in China, particularly for the treatment of compulsive behaviours.

A two-stage process facilitating microbial lipid production from N-acetylglucosamine by Cryptococcus curvatus cultured under non-sterile conditions.

N-acetylglucosamine (GlcNAc), the monomeric constituent of chitin, is rarely studied for lipid production by oleaginous species. This study demonstrated that Cryptococcus curvatus had a great capacity to convert GlcNAc into lipid with high yield using a two-stage production process. Optimal inoculum age and inoculation size strongly improved the two-stage lipid production efficiency. More interestingly, this process rendered superior lipid production under non-sterile condition. The acetate liberated from GlcNAc was consumed timely, while the NH4+ released was rarely assimilated. Lipid titre, lipid content and lipid yield reached 9.9 g/L, 56.9% and 0.23 g/g, respectively, which were significantly higher than those from the conventional process where cell growth and lipid accumulation were coupled. The resulting lipid samples had similar fatty acid compositional profiles to those of vegetable oil, suggesting their potential for biodiesel production. These findings strongly supported the two-stage process as an attractive strategy for better techno-economics of the chitin-to-biodiesel routes.

An intronic CYP46A1 polymorphism is associated with Alzheimer disease in a Chinese Han population.

Excess cholesterol is removed from the brain via hydroxylation mediated by cholesterol 24S-hydroxylase (CYP46), which is a mechanism of maintaining cholesterol homeostasis in the brain. The CYP46A1 gene has been suggested as a genetic risk factor for sporadic late-onset Alzheimer's disease (AD). In this report, we analyzed an intronic CYP46A1 single nucleotide polymorphism (SNP) in 508 sporadic AD patients and 549 controls in a Chinese Han population. Our results indicated that the distribution of CYP46A1 SNP rs754203 genotypes was significantly different in AD patients compared to controls (χ(2) = 6.59, P = 0.037). The frequency of at least one of CYP46A1 T allele (C/T or T/T) was higher in AD patients compared to controls (χ(2) = 6.58, P = 0.01). The age- and sex-adjusted odds ratio for the risk of AD in carriers of CYP46A1 T allele (C/T + T/T) was 1.69 (95 % confidence interval, 1.12-2.56). We conclude that this intronic polymorphism in CYP46A1 gene is associated with AD in a Chinese Han population, and the CYP46A1 T allele might be a risk factor for AD.

Lack of association of neprilysin gene polymorphisms with Alzheimer's disease in a southern Chinese community.

BACKGROUND: Increasing evidence suggests that neprilysin (NEP) may be the major degrading enzyme of amyloid beta (Abeta) in the brain and the NEP gene has been proposed as a candidate gene for Alzheimer's disease (AD). Association results between the NEP gene and AD are still preliminary. This study investigates the effect of the polymorphisms of -204G/C and 159C/T in the NEP gene on the development of sporadic Alzheimer's disease (SAD) in a southern Chinese community. METHOD: 236 sporadic late-onset AD patients were recruited from Guangzhou Psychiatric Hospital in southern China, and 332 healthy elderly controls were enrolled from three old age homes in suburban Guangzhou. NEP and ApoE genotype were determined by PCR-RFLP. RESULTS: No differences in genotypic and allelic frequencies of -204G/C and 159C/T polymorphisms in NEP were found between AD and control group (for -204G/C genotype: chi2 = 2.34, P > 0.05; for allele: chi2 = 2.31, P > 0.05; for 159C/T genotype: chi2 = 1.34, P > 0.05; for allele: chi2 = 0.88, P > 0.05). Neither was any difference found in genotypic and allelic frequency when stratified by sex or by ApoE epsilon4 allele (P > 0.05). CONCLUSIONS: Our results suggest that -204G/C and 159C/T polymorphisms of the NEP gene may not be associated with SAD. Moreover, both sex and ApoE epsilon4 allele do not affect the distribution of NEP gene polymorphisms.

Genetic association between low-density lipoprotein receptor-related protein gene polymorphisms and Alzheimer's disease in Chinese Han population.

Alzheimer's disease (AD) is the most common neurodegenerative disorders in the elderly. Low-density lipoprotein receptor-related protein (LRP), as a receptor of apolipoprotein E (APOE), APP, and alpha2 macroglobulin (alpha2-M), keeps the balance between degeneration and production of beta-amyloid protein (Abeta) clearance. Its gene had been defined as a candidate gene for AD, but the results were not universal. Total 496 AD patients and 478 controls were recruited in Chinese Han population and real-time PCR was used to detect the polymorphism of LRP C766T. Multiple logistic regression, Chi-square test and survival analysis were performed to explore the association. The distribution of LRP genotypes and alleles was significantly different between cases and controls, and T allele could reduce the risk for developing AD (OR of CT genotype: 0.57; 95% CI: 0.38-0.85, rho=0.003; OR of T allele: 0.57; 95% CI: 0.39-0.83, rho=0.003). TT genotype carriers had 5 years later for developing AD compared with CC genotype carriers, but survival analysis did not conform this (LRP TT vs. CT and CC log rank chi(2)=2.71, rho=0.26). The distribution of LRP C766T genotypes and alleles was different among different severity stratified by MMSE yet (rho=0.26). Our data suggested that the polymorphism of LRP C766T was strongly associated with AD and T allele might be a protective factor for AD in Chinese Han population.

Lack of association between the BDNF gene Val66Met polymorphism and Alzheimer disease in a Chinese Han population.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by excessive neuronal loss in specific regions of the brain. Among the areas most severely affected are the basal forebrain cholinergic neurons and their projection regions, the hippocampus and the cortex. Several lines of evidence have made brain-derived neurotrophic factor (BDNF) an important candidate gene conferring risk for AD. Recently, several reports investigated the association between a single nucleotide polymorphism (Val66Met, rs6265) of the BDNF gene and AD but yielded ambiguous results. To figure out the association of this single nucleotide polymorphism in the BDNF gene with sporadic AD in a Chinese Han population, we analyzed 513 patients with AD and 575 controls for the genetic association studies. Our results indicated that the distribution of the BDNF genotypes and alleles did not differ significantly. Similar results were observed when the AD and control groups were stratified by age/age at onset and sex. Our data also showed that in the Chinese Han population, the frequencies of the BDNF Met allele (46.5%) and Val allele (53.5%) were significantly different from ethnic groups from Italy, Japan and the USA. The present data revealed no significant effect of the genotypes on the age at onset for developing AD, and no significant association between the genotypes and the severity of the disease.

Gln192Arg polymorphism in paraoxonase 1 gene is associated with Alzheimer disease in a Chinese Han ethnic population.

BACKGROUND: Oxidative stress such as low-density lipoprotein (LDL) oxidation is thought to be an important mechanism in Alzheimer's disease (AD). Paraoxonase 1 (PON1), an enzyme located on high-density lipoprotein, can prevent LDL from oxidation to some extent. It is also a potent cholinesterase inhibitor and an arylesterase, combating organophosphate poisoning and metabolization of environmental neurotoxins which might be responsible for neurodegeneration with aging. We evaluated the association of Gln192Arg polymorphism in the PON1 gene with AD in a Chinese Han ethnic population. METHODS: Patients and age-matched controls were recruited from outpatient clinics and a population-based epidemiological survey, respectively. Gln192Arg polymorphism in the PON1 gene was detected by allele-specific PCR technique in 521 patients with AD and 578 healthy controls. RESULTS: The presence of at least one of PON1 R alleles (Q/R or R/R) was lower in AD patients than in the controls (82.7% vs 87.4%; chi(2) = 4.68, P = 0.03). PON1 gene R allele frequency was lower in AD patients than in the controls (60.7% vs 64.7%; chi(2) = 3.85, P = 0.05). One-way ANOVA showed that PON1 genotype had no effect on the age of onset for developing AD. Logistic regression analysis demonstrated the age and sex-adjusted odds ratio (OR) for the risk of AD in PON1 of PON1 R allele carriers was 0.71 (P = 0.044, 95% CI, 0.51 - 0.99). CONCLUSION: Our results indicate that Gln192Arg polymorphism in the PON1 gene is associated with AD, and PON1 R allele might be a protective factor for AD in a Chinese Han ethnic population.

[Paraoxonase 1 gene Gln192Arg polymorphism in and Alzheimer disease].

OBJECTIVE: The aim of this study was to evaluate the association of Gln192Arg polymorphism in paraoxonase 1 (PON1) gene with Alzheimer's disease (AD) in Chinese Han population. METHODS: Gln192Arg polymorphism in PON1 gene was detected with real-time PCR (RT-PCR) technique in 521 patients with AD and 578 healthy controls. RESULTS: The presence of at least one of PON1 R allele (Q/R or R/R) was lower in AD patients as compared with the controls (82.7% vs 87.4%; chi(2) = 4.68, P = 0.03). PON1 gene R allele frequency was lower in AD patients as compared with the controls (60.7% vs 64.7%; chi(2) = 3.85, P = 0.05). One-Way ANOVA showed that PON1 genotype had no effect on the age of onset of AD. Logistic regression analysis demonstrated that the age and sex-adjusted OR for the risk of AD in PON1 R allele carriers was 0.71 (P = 0.044, 95% CI = 0.51 - 0.99). CONCLUSION: Our results indicate that Gln192Arg polymorphism in PON1 gene is associated with AD and PON1 R allele might be a protective factor for AD in Chinese Han population.

The Fas gene A-670G polymorphism is not associated with sporadic Alzheimer disease in a Chinese Han population.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterized by excessive neuronal loss, intracellular neurofibrillary tangles and extracellular deposition of amyloid beta-peptide (Abeta). The Fas antigen is a cell surface receptor-mediating cell apoptosis. Several lines of evidence have made Fas/Fas ligand induced apoptosis play an important role in the pathogenesis of AD. Moreover, the Fas gene is located on chromosome 10q24.1, a region of linkage to late-onset AD. Several reports have investigated the association between a single nucleotide polymorphism (SNP) that is located at position -670 of Fas gene and AD, but yielded ambiguous results. To figure out the association of this SNP with sporadic AD in Chinese Han population, we have analyzed 509 patients with AD and 561 controls for the genetic association studies. Our results indicate that the distribution of the Fas genotypes (chi(2) = 0.66, P = 0.72) and alleles (chi(2) = 0.70, P = 0.40) did not differ significantly. The similar results were observed when AD and control groups were stratified by age/age at onset and sex (P > 0.10). The present data revealed no significant effect of the genotypes on the age of onset for developing AD, and no significant association between the genotypes and the severity of the disease.

[Gln192Arg polymorphism of the paraoxonase-1 gene is not associated with Alzheimer's disease in Chinese].

OBJECTIVE: To explore the relationship between paraoxonase-1 (PON1) gene Gln192Arg polymorphism and sporadic Alzheimer's disease (AD) in Chinese. METHODS: A total of 165 AD patients and 174 age-matched control subjects were enrolled in this study for examination of PON1 Gln192Arg and apolipoprotein E gene polymorphisms using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). RESULTS: The distribution of PON1 allelic and genotypic frequencies did not significantly differ between AD patients and the control subjects, even after the stratification by ApoE-epsilon4 status. CONCLUSION: Gln192Arg polymorphism of the PON1 gene is not associated with sporadic AD in Chinese.