Metabolic Engineering of Escherichia coli for Efficient Production of Pseudouridine.

Pseudouridine-incorporated mRNA vaccines can enhance protein expression and reduce immunogenicity, leading to a high demand for pseudouridine to be used in mRNA drug production. To achieve the low-cost production of pseudouridine, Escherichia coli was systematically modified to utilize inexpensive raw materials to efficiently produce pseudouridine. First, in the pyrimidine biosynthesis pathway, genes related to the precursor competing pathway and the negative regulator were deleted, which increased pseudouridine production. Second, two critical genes, pseudouridine-5'-phosphate glycosidase (psuG) and phosphatase genes from different bacteria, were screened and employed in various genetic constructs, and the pseudouridine yield of the optical strain increased to 599 mg/L. The accumulation of pseudouridine was further increased by the deletion of pseudouridine catabolism-related genes. Ultimately, the pseudouridine titer in a 5 L bioreactor reached 7.9 g/L, and the yield of pseudouridine on glucose was 0.15 g/g. Overall, a cell factory producing pseudouridine was successfully constructed and showed potential for industrial production.

Enhanced dewater efficiency for river sediment by top-to-bottom water transmitting channels with different materials.

Artificial top-to-bottom water transmitting channels made of threads of wool blend (WT), cotton (CT), flax (FT), and polyethylene (PET) were used to enhance the dewater efficiency for river sediment. In addition, the disordered channels composed of 3-mm-long WT segments mixed randomly into the river sediment were also employed. The most effective dewatering channels were found to be top-to-bottom WT channels with water absorption capacity of 8.7 ± 0.5 g · g-1 and volume compressibility of 2.94 ± 0.11. On the application of 0.1 MPa pressure to the mud surface, with initial water content of 60.0 ± 0.2 wt%, the water content obtained with channel material weight 0.411 wt% dry solids and channel to a mud cake height ratio of 0.95 upon 90-min dewatering was 39.6 ± 0.7 wt% with enhanced dewaterability, compared to that without channel addition, of 74.9 ± 0.9 kg · kg-1 · h-1. Using the same parameters, enhanced dewaterability was only 69.1 ± 0.3, 55.2 ± 2.8, and 9.1 ± 0.9 kg · kg-1 · h-1 for CT, FT, and PET channels, respectively. Moreover, the final water content of the mud cake dewatered in the presence of disordered WT channels at dosage 1.10 wt% was 49.8 ± 0.7 wt% with enhanced dewaterability of 5.9 ± 0.5 kg · kg-1 · h-1 only. These demonstrate that the compressibility of the water transmitting material is the main factor affecting dewatering efficiency with the water absorption capacity also being important.

Locating QTLs controlling overwintering seedling rate in perennial glutinous rice 89-1 (Oryza sativa L.).

A new cold tolerant germplasm resource named glutinous rice 89-1 (Gr89-1, Oryza sativa L.) can overwinter using axillary buds, with these buds being ratooned the following year. The overwintering seedling rate (OSR) is an important factor for evaluating cold tolerance. Many quantitative trait loci (QTLs) controlling cold tolerance at different growth stages in rice have been identified, with some of these QTLs being successfully cloned. However, no QTLs conferring to the OSR trait have been located in the perennial O. sativa L. To identify QTLs associated with OSR and to evaluate cold tolerance. 286 F12 recombinant inbred lines (RILs) derived from a cross between the cold tolerant variety Gr89-1 and cold sensitive variety Shuhui527 (SH527) were used. A total of 198 polymorphic simple sequence repeat (SSR) markers that were distributed uniformly on 12 chromosomes were used to construct the linkage map. The gene ontology (GO) annotation of the major QTL was performed through the rice genome annotation project system. Three main-effect QTLs (qOSR2, qOSR3, and qOSR8) were detected and mapped on chromosomes 2, 3, and 8, respectively. These QTLs were located in the interval of RM14208 (35,160,202 base pairs (bp))-RM208 (35,520,147 bp), RM218 (8,375,236 bp)-RM232 (9,755,778 bp), and RM5891 (24,626,930 bp)-RM23608 (25,355,519 bp), and explained 19.6%, 9.3%, and 11.8% of the phenotypic variations, respectively. The qOSR2 QTL displayed the largest effect, with a logarithm of odds score (LOD) of 5.5. A total of 47 candidate genes on the qOSR2 locus were associated with 219 GO terms. Among these candidate genes, 11 were related to cell membrane, 7 were associated with cold stress, and 3 were involved in response to stress and biotic stimulus. OsPIP1;3 was the only one candidate gene related to stress, biotic stimulus, cold stress, and encoding a cell membrane protein. After QTL mapping, a total of three main-effect QTLs-qOSR2, qOSR3, and qOSR8-were detected on chromosomes 2, 3, and 8, respectively. Among these, qOSR2 explained the highest phenotypic variance. All the QTLs elite traits come from the cold resistance parent Gr89-1. OsPIP1;3 might be a candidate gene of qOSR2.