Study on the mechanism of sodium ion inhibiting citric acid fermentation in Aspergillus niger.

Excessive sodium significantly inhibits citric acid fermentation by Aspergillus niger during the recycling of citric acid wastewater. This study aimed to elucidate the inhibition mechanism at the interface of physiology and transcriptomics. The results showed that excessive sodium caused a 22.3 % increase in oxalic acid secretion and a 147.6 % increase in H+-ATPase activity at the 4 h fermentation compared to the control. Meanwhile, a 13.1 % reduction in energy charge level and a 15.2 % decline in NADH content were found, which implied the effects on carbon metabolism and redox balance. In addition, transcriptomic analysis revealed that excessive sodium altered the gene expression profiles related to ATPase, hydrolase, and oxidoreductase, as well as pathways like glyoxylate metabolism, and transmembrane transport. These findings gained insights into the metabolic regulation of A. niger response to environmental stress and provided theoretical guidance for the construction of sodium-tolerant A. niger for industrial application.

Application of a Salt-Resistant In Situ Cross-Linked Terpolymer Gel for the Daqing Oilfield.

Pubei Block, which is a subdivision of Daqing Oilfield, presents a challenging environment for conformance control due to its high temperature (average 80 °C) and salinity (13,451 mg/L), making it difficult for the polyacrylamide-based gel to maintain the necessary gel strength. To address this issue, this study aims to evaluate the feasibility of using a terpolymer in situ gel system that provides greater temperature and salinity resistance and pore adaptation. The terpolymer used here consists of acrylamide, acrylamido-2-methylpropane sulfonic acid, and N,N'-dimethylacrylamide. We determined that a formula with a hydrolysis degree of 15.15%, a polymer concentration of 600 mg/L, and a polymer-cross-linker ratio of 2.8 yields the greatest gel strength. The hydrodynamic radius of the gel was found to be 0.39 µm, indicating no conflict with the pore and pore-throat sizes determined by the CT scan. In the core-scale evaluation, the gel treatment improved oil recovery by 19.88%, of which 9.23% was through gelant injection and 10.65% through post water injection. A pilot test began in 2019 and has continued for 36 months until now. Within this period, the oil recovery factor increased by 9.82%. The number is likely to keep going up until the water cut (so far 87.4%) reaches the economic limit.

Production of butanol from distillers' grain waste by a new aerotolerant strain of Clostridium beijerinckii LY-5.

A new aerotolerant strain of Clostridium beijerinckii LY-5 was isolated from the pit mud of the Chinese Baijiu-making process for butanol production. Plackett-Burman design and artificial neural network were used to optimize the fermentation medium and a total of 13.54 ± 0.22 g/L butanol and 19.91 ± 0.52 g/L ABE were attained under aerotolerant condition. Moreover, distillers' grain waste (DGW), the main by-product in the Baijiu production process, was utilized as potential substrate for butanol production. DGW was hydrolyzed by α-amylase and glucoamylase and then fermented after a detoxifying process of overliming. Butanol and ABE concentrations were 9.02 ± 0.18 and 9.57 ± 0.19 g/L with the yield of 0.21 and 0.23 g/g sugar, respectively. The higher ratio of butanol to ABE might be caused by the inhibitors in DGW medium affecting the metabolic pathways of C. beijerinckii LY-5 and approximately 1.48 ± 0.04 g/L isopropanol was found at the end of fermentation. This work highlights the feasibility of using DGW as a promising feedstock for butanol production by a new aerotolerant strain of C. beijerinckii LY-5, with benefit to the environment.

Full recycling of citric acid wastewater through anaerobic digestion, air-stripping and pH control.

Anaerobic digestion effluent (ADE) from the anaerobic digestion treatment of citric acid wastewater can be reused as a potential substitute for process water in the citric acid fermentation. However, excessive sodium contained in ADE significantly decreases citric acid production. In this paper, the inhibition mechanism of sodium on citric acid fermentation was investigated. We demonstrated that excessive sodium did not increase oxidative stress for Aspergillus niger, but reduced the pH of the medium significantly over the period 4-24 h, which led to lower activities of glucoamylase and isomaltase secreted by A. niger, with a decrease of available sugar concentration and citric acid production. ADE was pretreated by air-stripping prior to recycle and 18 g/L calcium carbonate was added at the start of fermentation to control the pH of the medium. The inhibition caused by ADE was completely alleviated and citric acid production substantially increased from 118.6 g/L to 141.4 g/L, comparable to the fermentation with deionized water (141.2 g/L). This novel process could decrease wastewater discharges and fresh water consumption in the citric acid industry, with benefit to the environment.

Higher prevalence of sexual transmitted diseases and correlates of genital warts among heterosexual males attending sexually transmitted infection clinics (MSCs) in Jiangmen, China: implication for the up-taking of STD related service.

BACKGROUND: Increasing burden of STDs is one of China's major public health concerns. However, only a limited number of studies have ever investigated the prevalence of these STDs, particular for genital warts and its correlates among heterosexual males attending STD clinics in China. In order to fill this gap, we conducted a cross-sectional study among MSCs in Jiangmen, China, between the years of 2009 and 2010. METHOD: The eligible participants were recruited from several STD-clinics in public hospitals. We collected demographic information and behaviors of the participants. After HIV and syphilis testing, we further checked whether the participants had genital warts and genital herpes. In addition, urine samples were collected from part of the participants for CT and NG testing. RESULTS: Of the 533 eligible participants, over three-fifths were aged 35 or below, nearly three quarters had no college degree, over three-fifths were residence of Jiangmen. The prevalence of HIV, syphilis, genital warts, genital herpes, CT and NG were 0.19%, 7.50%, 7.32%, 5.25%, 9.73% and 6.19%, respectively. Living with family members (versus living alone), no STD-related service in past year, experiencing STDs related symptoms in past year, and sex with FSWs in last three months were positively associated with genital warts, with adjusted ORs of 5.54 (95% CI 1.94-15.81), 2.26 (95% CI 1.08-4.74), 1.99 (95% CI 1.00-3.99) and 2.01 (95% CI 1.00-4.04), respectively. CONCLUSION: Our study indicates that the prevalence of STDs among MSCs in Jiangmen was high, which may further spread HIV among MSCs. Targeted interventions that focused on STDs related services uptake should be implemented urgently.

Rapid syphilis testing uptake for female sex workers at sex venues in Southern China: implications for expanding syphilis screening.

BACKGROUND: Accessibility of syphilis testing services is critical in syphilis control programs for female sex workers (FSWs), but few FSWs attend public STI clinics or other testing sites. Introduction of free rapid syphilis testing (RST) into outreach programs for FSWs will help improve test uptake. METHODS: Commercial sex venues were identified in two cities in South China. In cooperation with health advocacy organizations, health outreach teams from local public health or medical facilities approached all types of sex venues in study areas to offer free RST. Acceptability and uptake of RST among FSWs were evaluated. RESULTS: A total of 2812 FSWs were offered RST and 2670 (95.0%) accepted syphilis testing. 182 (6.8%) FSWs had a positive RST result among whom 136 (74.7%) were willing to attend an STD clinic for confirmatory testing and treatment. More than half (89, 66.4%) of those with syphilis were not willing to notify their sex partners. Multivariate logistic analysis showed that syphilis test uptake was associated with residing in Jiangmen (AOR, 1.78; 95% CI, 1.15-2.77), older age (AOR, 2.11, 95% CI, 1.17-3.79 for age of 31 years or above), and not working at a service venue (AOR, 1.60; 95% CI, 1.10-2.34). CONCLUSIONS: RST at sex venues is well accepted by FSWs when it is integrated into ongoing outreach services. Such programs provide excellent opportunities for expanding syphilis screening efforts among specific subgroups of FSW who are difficult to reach through clinic-based programs.

A twin response to twin epidemics: integrated HIV/syphilis testing at STI clinics in South China.

BACKGROUND: HIV testing is still stigmatized among many high-risk groups in China, whereas routine syphilis testing has been widely accepted at sexually transmitted infection (STI) clinics. This project used the platform of a rapid syphilis screening test to expand HIV test uptake. The objective of this study was to use multilevel modeling to analyze determinants of syphilis and HIV-testing uptake at STI clinics in China. METHODS: 2061 STI patients at 6 clinics in Guangdong Province were offered free rapid syphilis and free rapid HIV testing. Test uptake was defined by patient receipt of results and a multilevel model was used to analyze predictors of uptake. RESULTS: This was the first syphilis or HIV test for the large majority (1388, 77.7%) of participants. Syphilis test uptake and HIV test uptake were high (1681, 81.6%, syphilis test uptake; 1673, 81.2% HIV test uptake). HIV test uptake was significantly concordant with syphilis test uptake (τb = 0.89, P < 0.001). The most parsimonious model of refusing HIV test uptake included the following variables: being married, having a previous HIV test, being unaccompanied, and participating in the last 2 months of the study. CONCLUSIONS: STI clinic-based screening for syphilis and HIV represents an excellent opportunity for scaling up integrated services, especially in South China where syphilis and sexually transmitted HIV cases are both rapidly increasing. Effective integration of HIV testing into routine clinical practice requires an understanding not only of individual test uptake but also of the broader social context of HIV testing.

Integrated syphilis/HIV screening in China: a qualitative analysis.

BACKGROUND: The last decade has seen enormous advances in HIV treatment and care, but how to implement scaled up HIV testing, prevention, and treatment in low-income areas still presents a formidable public health challenge. South China faces expanding syphilis and sexually transmitted HIV epidemics, but health systems characteristics important for scaling up syphilis and HIV testing have not been defined. METHODS: A purposive sample to ensure public, private, and public-private hybrid STI clinic inclusion was selected in a South China city. Eight key informant interviews were conducted with the STI clinic manager, followed by eight focus group discussions with physicians. Data collection relied on a semi-structured format that included questions in each of the following domains: 1) clinical facilities; 2) laboratory capacity with a focus on syphilis/HIV diagnosis; 3) clinic personnel; 4) physical space with a focus on locations to disclose confidential results; 5) financial support. RESULTS: Public STI clinics had free syphilis testing/treatment and laboratory facilities to perform essential syphilis and HIV tests. However, despite serving a large number of STI patients, private STI clinics lacked nontreponemal syphilis testing, HIV testing, and had fewer connections to the public health infrastructure. Formally trained assistant physicians were 2.5 times as common as physicians at STI clinics. Only one of the 8 sites had onsite voluntary counseling and testing (VCT) services available. CONCLUSION: These STI case studies reveal the potential for expanding integrated syphilis/HIV services at public STI clinics in China. More health services research is needed to guide scale-up of syphilis/HIV testing in China.