Molecular Modification Enhances Xylose Uptake by the Sugar Transporter KM_SUT5 of Kluyveromyces marxianus.

This research cloned and expressed the sugar transporter gene KM_SUT5 from Kluyveromyces marxianus GX-UN120, which displayed remarkable sugar transportation capabilities, including pentose sugars. To investigate the impact of point mutations on xylose transport capacity, we selected four sites, predicted the suitable amino acid sites by molecular docking, and altered their codons to construct the corresponding mutants, Q74D, Y195K, S460H, and Q464F, respectively. Furthermore, we conducted site-directed truncation on six sites of KM_SUT5p. The molecular modification resulted in significant changes in mutant growth and the D-xylose transport rate. Specifically, the S460H mutant exhibited a higher growth rate and demonstrated excellent performance across 20 g L-1 xylose, achieving the highest xylose accumulation under xylose conditions (49.94 µmol h-1 gDCW-1, DCW mean dry cell weight). Notably, mutant delA554-, in which the transporter protein SUT5 is truncated at position delA554-, significantly increased growth rates in both D-xylose and D-glucose substrates. These findings offer valuable insights into potential modifications of other sugar transporters and contribute to a deeper understanding of the C-terminal function of sugar transporters.

Enzymatic biotransformation of Rb3 from the leaves of Panax notoginseng to ginsenoside rd by a recombinant ß-xylosidase from Thermoascus aurantiacus.

Given the important pharmacological activity of ginsenoside Rd but its low content in plants, the production of Rd by enzymatic transformation is of interest. In this study, a ß-xylosidase gene Ta-XylQS from Thermoascus aurantiacus was cloned and overexpressed in Komagataella phaffii. Purified recombinant Ta-XylQS specifically hydrolyzes substrates with xylosyl residues at the optimal pH of 3.5 and temperature of 60 °C. This study established a process for producing Rd by transforming ginsenoside Rb3 in the saponins of Panax notoginseng leaves via recombinant Ta-XylQS. After 60 h, 3 g L- 1 of Rb3 was transformed into 1.46 g L- 1 of Rd, and the maximum yield of Rd reached 4.31 g kg- 1 of Panax notoginseng leaves. This study is the first report of the biotransformation of ginsenoside Rb3 to Rd via a ß-xylosidase, and the established process could potentially be adopted for the commercial production of Rd from Rb3.

Xylitol fermentation characteristics with a newly isolated yeast Wickerhamomyces anomalus WA.

Xylitol is an increasingly popular functional food additive, and the newly isolated yeast Wickerhamomyces anomalus WA has shown extensive substrate utilization capability, with the ability to grow on hexose (d-galactose, d-glucose, d-mannose, l-fructose, and d-sorbose) and pentose (d-xylose and l-arabinose) substrates, as well as high tolerance to xylose at concentrations of up to 300 g/L. Optimal xylitol fermentation conditions were achieved at 32 °C, 140 rpm, pH 5.0, and initial cell concentration OD600 of 2.0, with YP (yeast extract 10 g/L, peptone 20 g/L) as the optimal nitrogen source. Xylitol yield increased from 0.61 g/g to 0.91 g/g with an increase in initial substrate concentration from 20 g/L to 180 g/L. Additionally, 20 g/L glycerol was found to be the optimal co-substrate for xylitol fermentation, resulting in an increase in xylitol yield from 0.82 g/g to 0.94 g/g at 140 rpm, enabling complete conversion of xylose to xylitol.

Pediatric Spinal Cord Injury without Radiographic Abnormality: The Beijing Experience.

STUDY DESIGN: Retrospective study. OBJECTIVE: To describe the epidemiology and clinical outcomes of pediatric patients with spinal cord injury (SCI) without radiographic abnormality (SCIWORA) in mainland China for the first time. SUMMARY OF BACKGROUND DATA: SCIWORA is a syndrome that often occurs in children mainly due to the unique biomechanics of the pediatric spine. Although there have been numerous retrospective studies on pediatric SCIWORA, and mainland China has more patients with SCI than anywhere else, pediatric patients with SCIWORA in mainland China has not been described in any study. METHODS: Review of all cases with SCIWORA at Beijing Children's Hospital between July 2007 and December 2019. RESULTS: Of the 189 pediatric patients with SCI 140 had SCIWORA (age: 5.65 ±â€Š2.60 years, male-to-female ratio: 2:5). Main causes of injuries were sports (41%, mostly backbend), falls (27%), traffic accidents (10%), and violence (8%). Lesions were located at the thoracic (77%), cervical (10%), multiple (5%), and lumbar (4%) levels. Incubation period was 2 ±â€Š6 hours. Pathological characteristics of SCI were detected in 96% patients by magnetic resonance imaging (MRI). Based on the American Spinal Injury Association impairment scale (AIS), many patients had complete impairment (50% AIS A, 45% AIS B/C/D, 1% AIS E). Particularly, the five patients with normal MRI tended to have mild injury (AIS D) (P < 0.001), but they still showed abnormal reflex. In the one patient who could not be graded at all by AIS, his only functional deficits were abnormal upper and lower limb muscle tones. A total of 59% patients were treated with methylprednisolone, dexamethasone, or both. Out of 76 patients 59 showed neurological improvement before discharge. The only association among age, cause of injury, level of lesion, incubation period, AIS grade, type of corticosteroid therapy, and neurological improvement was between level of lesion and AIS grade (P < 0.001). CONCLUSION: Demographic and clinical differences exist in patients with SCIWORA. MRI and detailed neurological examinations should both be performed for proper diagnosis. There is still a need to develop better treatment strategy for these patients.Level of Evidence: 4.