[This corrects the article DOI: 10.1016/j.apsb.2024.03.030.].

L-valine is an important branched-chain amino acid widely used in the food, pharmaceutical, and feed industries. Microbial fermentation has become the primary production method for L-valine. However, current industrial production still faces issues such as inefficient carbon flux utilization, imbalance in cofactor supply and demand, and suboptimal fermentation processes, which limit the efficient synthesis of L-valine. To further enhance the production performance of L-valine, In this study, metabolic engineering was conducted for a previously constructed Escherichia coli strain with a high yield of L-valine to optimize carbon flux distribution and balance cofactor consumption. Dual-phase oxygen-controlled fermentation was carried out to enhance L-valine production. Firstly, to address the pyruvate loss, we knocked out multiple competing pathway genes (ldhA, poxB, pflB, frdA, and pta), which resulted in a 48% increase in flask yield of the constructed strain VL-04. Next, we optimized the cofactor supply and demand balance by replacing ilvE with bcd (NADH-preferential) from Bacillus subtilis to construct the strain VL-06, which achieved a flask yield of 22.80 g/L, a further improvement of 25.8%. Subsequently, the fermentation conditions of VL-06 were optimized in a 5 L bioreactor with dual-phase oxygen-controlled fermentation. After optimization, the L-valine production reached 86.44 g/L in 26 h, with a glucose-to-acid conversion rate of 44.08% and a production intensity of 3.32 g/(L·h). This study not only shortens the time for L-valine production but also improves the economic efficiency, providing insights for similar fermentation processes employing dual-phase oxygen control.
Metabolic Engineering/methods* ; Escherichia coli/genetics* ; Valine/biosynthesis* ; Fermentation ; Bacillus subtilis/genetics*

Objective:To discuss the repairment effect of intra-articular injection of adipose derived stem cells(ADSCs)on articular cartilage destruction in the temporomandibular joint osteoarthritis(TMJOA)model rabbits,and to clarify the possible mechanism.Methods:Twenty-seven rabbits were randomly divided into control group,model group,and ADSCs group.The ADSCs of the rabbits were extracted and cultured.The rabbit TMJOA model was prepared by monosodium-iodoacetate(MIA)injection technique.The temporomandibular joint cavity of the TMJOA model rabbits in ADSCs group was given two continuous intra-articular injections of 1.0×106 mL-1 ADSCs,while the rabbits in control and model group were given sequivalent volume of saline into the temporomandibular joint cavity.After 8 weeks,Micro-CT scan was performed on the temporomandibular joints of the rabbits in various groups;the bone volume fraction(BV/TV),bone surface area/bone volume(BS/BV),trabecular thickness(Tb.Th),trabecular separation(Tb.Sp),and trabecular number(Tb.N)of condyles tissue of the rabbits in various groups were analyzed;HE staining was used to observe the pathomorphology of condyles tissue of the rabbits in various groups;immunohistochemistry was used to detect the localization and expression levels of SRY-related high mobility group box gene 9(SOX9),matrix metalloproteinase-13(MMP-13),and vascular endothelial growth factor(VEGF)proteins in condyles tissue of the rabbits in various groups;Western blotting method was used to detect the expression levels of SOX9,MMP-13,and VEGF proteins in condyles tissue of the rabbits in various groups.Results:The micro-CT scan results showed that compared with control group,the BV/TV,Tb.Th,and Tb.N of condyles tissue of the rabbits in model group were significantly decreased(P<0.05),while the BS/BV and Tb.Sp were significantly increased(P<0.05);compared with model group,the BV/TV,Tb.Th,and Tb.N in condyles tissue of the rabbits in ADSCs group were significantly increased(P<0.05),and the BS/BV and Tb.Sp were significantly decreased(P<0.05).The HE staining results showed that the condylar cartilage surface of the rabbits in control group was smooth with clear layers and intact structure;compared with control group,the surface of condyles tissue of the rabbits in model group was irregular with thickened hypertrophic layer and areas of cell depletion and clustering;compared with model group,the pathological damage of condyles tissue of the rabbits in ADSCs group was significantly decreased.The immunohistochemical staining results showed that compared with control group and ADSCs group,the number of brown granule in condyles tissue of the rabbits in model group was increased,mainly concentrated in the hypertrophic layer,especially in the bone cartilage junction site and the expression levels of SOX9,MMP-13,and VEGF proteins in condyles tissue of the rabbits in model group were significantly increased(P<0.05);compared with model group,the number of brown granule in condyles tissue of the rabbits in ADSCs group was significantly decreased,and the expression levels of SOX9,MMP-13,and VEGF proteins were significantly decreased(P<0.05).The Western blotting results showed that compared with control group,the expression levels of SOX9,MMP-13,and VEGF proteins in condyles tissue of the rabbits in model group were significantly increased(P<0.05);compared with model group,the expression levels of SOX9,MMP-13,and VEGF proteins in condyles tissue of the rabbits in ADSCs group were significantly decreased(P<0.05).Conclusion:Intra-articular injection of ADSCs can effectively repair the cartilage destruction in TMJOA,alleviate the cartilage injury,and mitigate the progression of osteoarthritis.

Objective:This study aims to evaluate the quality and explore the preliminary clinical applications of a domestically developed hepatitis D virus nucleic acid quantification reagent (abbreviated as"domestic HDV RNA reagent").Methods:The sensitivity and accuracy of the reagent were evaluated in accordance with the WHO HDV RNA international standard, employing the Bio-Rad CFX Opus 96 real-time fluorescence quantitative PCR analysis system. Serial dilutions of pseudo-viruses or cell culture-derived virus were used to determine the linear range of the domestic HDV RNA reagent. Specificity was assessed using positive samples of HAV, HBV, HCV infection, and HEV national reference materials. Precision was evaluated with samples at both high and low concentrations. In a comparative analysis, 30 HDV IgG positive samples were tested using both the domestic HDV RNA reagent and the RoboGene HDV RNA kit based on the ABI 7500 FAST DX system. The Pearson correlation coefficient (r) was used to examine the correlation between the two reagents.Results:The domestic HDV RNA reagent demonstrated a high sensitivity of up to 6 IU/ml, consistent with that of the comparator reagent. The calibration curve for WHO HDV RNA standards had a slope of -3.286, with an amplification efficiency of 101.6%. The linear detection range spanned from 10 to 10 8 IU/ml for eight HDV genotypes. The domestic HDV RNA reagent exhibited exceptional specificity, without cross-reactivity observed with HAV, HBV, HCV, or HEV. Accuracy assessments at five concentration levels met the required standards, with intra-assay precision coefficient of variation ( CV) ranging from 1.20% to 4.20%, and inter-assay precision CV from 1.20% to 7.90%. The detection results for HDV IgG positive samples were highly correlated with the comparator reagent ( r=0.984, P<0.001), achieving a diagnostic accuracy of 100% compared to sequencing results. Conclusion:In this study, the domestic HDV RNA reagent possesses excellent specificity, accuracy, precision, and a broad linear range, attaining a sensitivity level on par with international reagents of the same type.

Objective To understand how warfarin inhibition is hindered by the vitamin K epoxide reductase(VKORC1)resistant mutations.Methods An electrophoretic mobility assay was conducted based on the principle that binding with warfarin resulted in changes in VKORC1 electrophoretic mobility.The activity of VKORC1 and the half maximal inhibitory concentration(ICs0)of warfarin inhibiting VKORC1 were detected by ELISA.These experiments evaluated the binding ability of VKORC1 resistant mutants to warfarin.Results With warfarin bound,VKORC1 was protected from N-ethylmaleimide(NEM)modification and showed increased electrophoretic mobility,which was dependent on an unmodified cysteine on the flexible transmembrane helix 1(TM1)of VKORC1.In-creasing the warfarin concentration could shift more VKORC1 towards the species with the fast mobility.Compared to the wildtype VKORC1,the fast mobility fraction became less or disappeared in warfarin-resistant mutants,indi-cating weakened binding of warfarin.In addition,VKORC1 mutants with the weaker electrophoretic mobility shift indicated the stronger warfarin resistant.Conclusion Weakened warfarin binding is the primary cause of warfarin resistance.

Objective:To systematically evaluate the qualitative research on experience of fear of falling in the elderly, so as to provide theoretical basis for nursing practice.Methods:Qualitative researches on the fear of falling among the elderly were systematically searched in PubMed, Web of Science, Embase, Cochrane Library, China National Knowledge Infrastructure, WanFang Data, VIP, and China Biology Medicine disc. The search period was from database establishment to November 5, 2023. The quality of literature was evaluated using the quality evaluation criteria for qualitative research of the Australia Joanna Briggs Institute Evidence-Based Health Care Center, and the results were integrated using the Meta-synthesis.Results:A total of 13 articles were included, 44 themes were extracted, categorized into 12 categories, and refined into four integrated results, namely perception of fear of falling, influencing factors of fear of falling, coping strategies in attitude and behavior, and multidimensional needs for rehabilitation nursing.Conclusions:Medical and nursing staff should pay attention to and understand the fear of falling among the elderly, evaluate their fear of falling from multiple dimensions and dynamically, provide personalized guidance based on coping behaviors, create support systems to alleviate their fear of falling and meet their multidimensional needs, so as to improve their quality of life.

Objective:To discuss the effect of temperature-controlled shrinkage polytrimethylene carbonate(PTMC)/polyvinylpyrrolidone(PVP)nanofiber membrane on the biological behavior of mouse fibroblasts and the repairment effect on full-thickness skin defects in the rats,and to clarify the potential mechanism.Methods:The murine L929 fibroblast cells were used in the in vitro experiments and were divided into control group and experimental group(treated with PTMC/PVP nanofiber membranes).The proliferation activities of the cells in two groups were detected by CCK-8 assay;the numbers of live/dead cells in two groups were observed by live/dead cell staining;the morphology of the cells was observed by cytoskeletal staining.A total of 12 six-week-old male SD rats were selected in the in vivo experiment,and were randomly divided into control group and experimental group,and there were six rats in each group.The full-thickness skin defect model was established,and the rats in experimental group were treated with PTMC/PVP nanofiber membranes.The photographs were taken after operation,and the wound healing rates of the cells in two groups were calculated on the 0,3rd,6th,and 12th days.On the 6th and 12th days after operation,the skin samples around the wound of the rats in two groups were taken,and the histopathology of the would skin and adjacent tissue was detected by HE staining;the collagen deposition in wound skin tissue of the rats in two groups was observed by Masson trichrome staining;the numbers of angiogenesis in wound skin tissue of the rats were detected by CD31 immunohistochemical staining.Results:The CCK-8 assay results showed that the proliferation activity of the cells in experimental group showed an increasing trend on the 1st,3st,and 5st days,and there was no significant difference in the proliferation activities of the cells bewteen experimental group and control group(P＞0.05).The live/dead cell staining experiment results showed that compared with control group,the cell density and number of the cells in experimental group had no significant changes,and were predominantly live cells.The cytoskeletal staining results showed that the cells in experimental and control groups appeared spindle-shaped and well-spread.In the in vivo experiments,on the 3rd,6th,and 12th days,compared with control group,the wound healing rates of the cells in experimental group were increased(P＜0.01),and the wound healing rate of the cells was 95.45％on the 12th day,indicating nearly complete healing of the wound.The HE staining showed that on the 12th day,the wound skin structure of the cells in experimental group was more similar to the normal skin,and there was abundant granulation tissue,regular epidermal structure,and new blood vessel formation.The Masson trichrome staining results showed that compared with control group,the collagen deposition in wound tissue of the rats in experimental group was increased.The immunohistochemical staining results showed that the expression of CD31 in wound tissue of the rats in experimental group was increased,indicating the increasing of the number of angiogenesis.Conclusion:The PTMC/PVP thermoresponsive nanofiber membranes exhibit good biocompatibility and can promote the repairment of full-thickness skin defects in the rats;its mechanism may be related to the enhancement of proliferation activity of the basal cells.

Objective To explore the current status and potential subtypes of frailty among family caregivers of patients with dementia,and to analyze the related influencing factors of different subtypes.Methods Dementia patients and their family caregivers in 8 community health service centers in Shanghai from June to October 2023 were recruited by convenience sampling.General information questionnaire,Tilburg Frailty Indicator(TFI),Pittsburgh Sleep Quality Index(PSQI),Self-Rating Depression Scale(SDS),Zarit Caregiver Burden Interview(ZBI),and Connor-Davidson Resilience Scale(CD-RISC)were conducted for investigation.Latent profile analysis was used to explore the potential subtypes of frailty among family caregivers of patients with dementia.The influencing factors associated with the potential subtypes were identified by univariate analysis and multivariate Logistic regression analysis.Results A total of 470 family caregivers of patients with dementia were surveyed,and 46.17％of them suffered from frailty.Frailty among family caregivers of patients with dementia can be classified into 3 potential subtypes:comprehensive-low frailty subtype(70.64％),psychosocial-medium frailty subtype(19.57％),and physical-high frailty subtype(9.79％).Family caregivers of patients with dementia who had poor sleep quality and suffered from 2 or more chronic diseases were more likely to be classified into the physical-high frailty subtype(P＜0.05).Family caregivers of patients with dementia who had higher levels of depression,lower mastery levels of caregiving knowledge and skills and spousal caregivers were more likely to be classified into the psychosocial-medium frailty subtype(P＜0.05).Family caregivers of patients with dementia who had higher levels of resilience were more likely to be classified into the comprehensive-low frailty subtype(P＜0.05).Conclusion The incidence of frailty among family caregivers of patients with dementia is at a high level with significant heterogeneity.It is suggested that medical staff should pay attention to the frailty of family caregivers,with a focus on family caregivers in the psychosocial-medium frailty subtype or physical-high frailty subtype,and take timely and targeted interventions according to the characteristics and influencing factors of different subtypes,so as to prevent or delay the occurrence and development of frailty.

Objective:To study the clinical characteristics of patients with brucella bloodstream infection in different age groups, and provide a basis for clinicians to take targeted diagnosis and treatment measures. Methods:Demographic data and general condition (age, sex, occupation, location, onset season, source of infection, clinical stage), clinical characteristics (main clinical symptoms and complications), and laboratory test results (routine and pathogenic tests) of adult patients with brucella bloodstream infection admitted to the Affiliated Hospital of Chengde Medical College from January 2015 to January 2020 were collected. According to the age stratification standards recommended by the World Health Organization, the patients were divided into a young group (18 - 44 years old), a middle-aged group (45 - 59 years old), and an elderly group (≥60 years old), and various indicators among different age groups were compared and analyzed. Results:A total of 75 patients were included, including 15 cases (20.00%) in the young group, 37 cases (49.33%) in the middle-aged group, and 23 cases (30.67%) in the elderly group. Among them, 61 cases (81.33%) were males and 14 cases (18.67%) were females, with statistically significant differences in gender ratios among different age groups (χ 2 = 7.28, P = 0.021). The majority of patients were farmers (64 cases, 85.33%), and 92.00% (69/75) of the patients came from rural areas. The main sources of infection were infected cattle and sheep, and contaminated food (39 cases, 52.00%). The main season of onset was spring and summer (45 cases, 60.00%). The clinical staging was mainly in the acute phase (66 cases, 88.00%). In terms of clinical symptoms, the young group of patients had no symptoms of low back pain, while the incidence rates of low back pain in the middle-aged and elderly groups were 35.14% (13/37) and 30.43% (7/23), respectively. There was a statistically significant difference between the three groups (χ 2 = 6.98, P = 0.031). In terms of complications, there were no cases of concurrent spondylitis in the young group of patients. The incidence rates of spondylitis in the middle-aged and elderly groups were 32.43% (12/37) and 34.78% (8/23), respectively. There was a statistically significant difference among the three groups (χ 2 = 6.86, P = 0.032). In terms of routine laboratory examinations, there were statistically significant differences in the proportion of blood lymphocytes and albumin levels among patients of different age groups ( F = 3.41, 3.27, P = 0.038, 0.044). In terms of pathogenic examination, there was a statistically significant difference in the median alarm time for positive blood culture among patients of different age groups ( H = 9.54, P = 0.008), with the middle-aged group having the longest (66.24 h) and the elderly group having the shortest (58.80 h). Conclusions:The clinical characteristics of patients with brucella bloodstream infection vary among different age groups, middle-aged and elderly patients are prone to low back pain symptoms, accompanied by spondylitis. Clinicians should pay attention to the patient's own characteristics and provide targeted diagnosis and treatment.