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BACKGROUND: Sucrose is an naturally abundant and easily fermentable feedstock for various biochemical production processes. By now, several sucrose utilization pathways have been identified and characterized. Among them, the pathway consists of sucrose permease and sucrose phosphorylase is an energy-conserving sucrose utilization pathway because it consumes less ATP when comparing to other known pathways. Bacillus amyloliquefaciens NK-1 strain can use sucrose as the feedstock to produce poly-γ-glutamic acid (γ-PGA), a highly valuable biopolymer. The native sucrose utilization pathway in NK-1 strain consists of phosphoenolpyruvate-dependent phosphotransferase system and sucrose-6-P hydrolase and consumes more ATP than the energy-conserving sucrose utilization pathway. RESULTS: In this study, the native sucrose utilization pathway in NK-1 was firstly deleted and generated the B. amyloliquefaciens 3Δ strain. Then four combination of heterologous energy-conserving sucrose utilization pathways were constructed and introduced into the 3Δ strain. Results demonstrated that the combination of cscB (encodes sucrose permease) from Escherichia coli and sucP (encodes sucrose phosphorylase) from Bifidobacterium adolescentis showed the highest sucrose metabolic efficiency. The corresponding mutant consumed 49.4% more sucrose and produced 38.5% more γ-PGA than the NK-1 strain under the same fermentation conditions. CONCLUSIONS: To our best knowledge, this is the first report concerning the enhancement of the target product production by introducing the heterologous energy-conserving sucrose utilization pathways. Such a strategy can be easily extended to other microorganism hosts for reinforced biochemical production using sucrose as substrate.

BACKGROUND: Poly-γ-glutamic acid (γ-PGA) is a valuable polymer with glutamate as its sole precursor. Enhancement of the intracellular glutamate synthesis is a very important strategy for the improvement of γ-PGA production, especially for those glutamate-independent γ-PGA producing strains. Corynebacterium glutamicum has long been used for industrial glutamate production and it exhibits some unique features for glutamate synthesis; therefore introduction of these metabolic characters into the γ-PGA producing strain might lead to increased intracellular glutamate availability, and thus ultimate γ-PGA production. RESULTS: In this study, the unique glutamate synthesis features from C. glutamicum was introduced into the glutamate-independent γ-PGA producing Bacillus amyloliquefaciens NK-1 strain. After introducing the energy-saving NADPH-dependent glutamate dehydrogenase (NADPH-GDH) pathway, the NK-1 (pHT315-gdh) strain showed slightly increase (by 9.1%) in γ-PGA production. Moreover, an optimized metabolic toggle switch for controlling the expression of ɑ-oxoglutarate dehydrogenase complex (ODHC) was introduced into the NK-1 strain, because it was previously shown that the ODHC in C. glutamicum was completely inhibited when glutamate was actively produced. The obtained NK-PO1 (pHT01-xylR) strain showed 66.2% higher γ-PGA production than the NK-1 strain. However, the further combination of these two strategies (introducing both NADPH-GDH pathway and the metabolic toggle switch) did not lead to further increase of γ-PGA production but rather the resultant γ-PGA production was even lower than that in the NK-1 strain. CONCLUSIONS: We proposed new metabolic engineering strategies to improve the γ-PGA production in B. amyloliquefaciens. The NK-1 (pHT315-gdh) strain with the introduction of NADPH-GDH pathway showed 9.1% improvement in γ-PGA production. The NK-PO1 (pHT01-xylR) strain with the introduction of a metabolic toggle switch for controlling the expression of ODHC showed 66.2% higher γ-PGA production than the NK-1 strain. This work proposed a new strategy for improving the target product in microbial cell factories.

In the Ming and Qing dynasties, the image materials of woodcarving furniture in Suzhou area are as important as the actual furniture, which are also valuable material information on the living customs of Suzhou in the Ming and Qing dynasties. From the perspective of imageology, this article analyzes the shape, category, style and other representative works of Su-style furniture’s woodcarving visual image, hoping to provide a reference for the research and design of regional furniture carving.

Hongmu is mostly used in furniture. The generation of corner materials in the production process of furniture causes unnecessary waste. Based on the current status of the use of leftover materials, this paper focuses on the feasibility of Hongmu materials in cultural creative design. It puts forward suggestions for the development of leftover materials and cultural creative products to help designers and enterprises use leftover materials more effectively and to maximize the value and cultural connotation.

Summary: Poly‐γ‐glutamic acid (γ‐PGA) is a biocompatible and biodegradable polypeptide with wide‐ranging applications in foods, cosmetics, medicine, agriculture and wastewater treatment. Bacillus amyloliquefaciens LL3 can produce γ‐PGA from sucrose that can be obtained easily from sugarcane and sugar beet. In our previous work, it was found that low intracellular glutamate concentration was the limiting factor for γ‐PGA production by LL3. In this study, the γ‐PGA synthesis by strain LL3 was enhanced by chromosomally engineering its glutamate metabolism‐relevant networks. First, the downstream metabolic pathways were partly blocked by deleting fadR, lysC, aspB, pckA, proAB, rocG and gudB. The resulting strain NK‐A6 synthesized 4.84 g l−1 γ‐PGA, with a 31.5% increase compared with strain LL3. Second, a strong promoter PC2up was inserted into the upstream of icd gene, to generate strain NK‐A7, which further led to a 33.5% improvement in the γ‐PGA titre, achieving 6.46 g l−1. The NADPH level was improved by regulating the expression of pgi and gndA. Third, metabolic evolution was carried out to generate strain NK‐A9E, which showed a comparable γ‐PGA titre with strain NK‐A7. Finally, the srf and itu operons were deleted respectively, from the original strains NK‐A7 and NK‐A9E. The resulting strain NK‐A11 exhibited the highest γ‐PGA titre (7.53 g l−1), with a 2.05‐fold improvement compared with LL3. The results demonstrated that the approaches described here efficiently enhanced γ‐PGA production in B. amyloliquefaciens fermentation. [ABSTRACT FROM AUTHOR]