Enhancement of transparent hydrogel sanxan production in Sphingomonas sanxanigenens NX02 via rational and random gene manipulation

Wu, Mengmeng; Su, Zhong; Tian, Xuefeng; Shen, Yaqi; Qu, Jianmei; Dai, Xiaohui; Wei, Weiying; Li, Guoqiang; Ma, Ting

doi:10.1016/j.carbpol.2018.02.027

Cited by 6 publications

(4 citation statements)

References 27 publications

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“…There are eight copies of phbC , seven copies of phbB , and nine copies of phbA in the genome of S. sanxanigenens NXdE (shown in Fig. 1 ) [ 38 ]. In recent years, some researchers isolated a novel Sphingomonas sp.…”

Section: Resultsmentioning

confidence: 99%

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Co-utilization of glucose and xylose for the production of poly-β-hydroxybutyrate (PHB) by Sphingomonas sanxanigenens NX02

Ming,

Li,

Shi

et al. 2023

Microb Cell Fact

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Background Poly-β-hydroxybutyrate (PHB), produced by a variety of microbial organisms, is a good substitute for petrochemically derived plastics due to its excellent properties such as biocompatibility and biodegradability. The high cost of PHB production is a huge barrier for application and popularization of such bioplastics. Thus, the reduction of the cost is of great interest. Using low-cost substrates for PHB production is an efficient and feasible means to reduce manufacturing costs, and the construction of microbial cell factories is also a potential way to reduce the cost. Results In this study, an engineered Sphingomonas sanxanigenens strain to produce PHB by blocking the biosynthetic pathway of exopolysaccharide was constructed, and the resulting strain was named NXdE. NXdE could produce 9.24 ± 0.11 g/L PHB with a content of 84.0% cell dry weight (CDW) using glucose as a sole carbon source, which was significantly increased by 76.3% compared with the original strain NX02. Subsequently, the PHB yield of NXdE under the co-substrate with different proportions of glucose and xylose was also investigated, and results showed that the addition of xylose would reduce the PHB production. Hence, the Dahms pathway, which directly converted D-xylose into pyruvate in four sequential enzymatic steps, was enhanced by overexpressing the genes xylB, xylC, and kdpgA encoding xylose dehydrogenase, gluconolactonase, and aldolase in different combinations. The final strain NX02 (ΔssB, pBTxylBxylCkdpgA) (named NXdE II) could successfully co-utilize glucose and xylose from corn straw total hydrolysate (CSTH) to produce 21.49 ± 0.67 g/L PHB with a content of 91.2% CDW, representing a 4.10-fold increase compared to the original strain NX02. Conclusion The engineered strain NXdE II could co-utilize glucose and xylose from corn straw hydrolysate, and had a significant increase not only in cell growth but also in PHB yield and content. This work provided a new host strain and strategy for utilization of lignocellulosic biomass such as corn straw to produce intracellular products like PHB.

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Section: Resultsmentioning

confidence: 99%

“…The strain NX02 can naturally utilize glucose and xylose simultaneously to produce bio-products [ 38 ], and its derivative strain NXdE also has this property. Based on this feature, we tested the possibility of strain NXdE co-utilizing glucose and xylose to produce PHB.…”

Section: Resultsmentioning

confidence: 99%

Co-utilization of glucose and xylose for the production of poly-β-hydroxybutyrate (PHB) by Sphingomonas sanxanigenens NX02

Ming,

Li,

Shi

et al. 2023

Microb Cell Fact

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“…In addition, some of the enzymes in the carotenoid and PHB synthetic pathways are NADP(H)-dependent reactions. Wu et al have reported that the block of PHB in Sphingomonas sanxanigenens NX02 may break the balance of NADPH and NADP + of the whole metabolic network, resulting in the decrease of exopolysaccharide (EPS) (15).…”

Section: Discussionmentioning

confidence: 99%

A Carotenoid- and Poly-β-Hydroxybutyrate-Free Mutant Strain of Sphingomonas elodea ATCC 31461 for the Commercial Production of Gellan

Luo

et al. 2019

mSphere

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Gellan gum is a microbial exopolysaccharide, produced after aerobic fermentation using the Gram-negative bacterium strain Sphingomonas elodea ATCC 31461. Due to its unique structure and excellent physical characteristics, gellan gum has a broad range of applications in food, pharmaceutical, and other industries where it is used for stabilizing, emulsifying, thickening, and suspending. During the fermentative production of gellan, strain ATCC 31461 also accumulates large amounts of the metabolic by-products yellow carotenoid pigments and poly-β-hydroxybutyrate (PHB), which is decreasing the gellan production and increasing processing costs. A pigment PHB-free mutant was obtained by knocking out the phytoene desaturase gene (crtI) in the carotenoid biosynthetic pathway and the phaC gene, encoding a PHB synthase for the polymerization of PHB. Unfortunately, the double gene knockout mutant produced only 0.56 g liter−1 gellan. Furthermore, blocking PHB and carotenoid synthesis resulted in the accumulation of pyruvate, which reduced gellan production. To elevate gellan production, combined UV irradiation and ethyl methanesulfonate (EMS) mutagenesis treatment were used. A mutant strain with the same level of pyruvate as that of the wild-type strain and higher gellan production was isolated (1.35 g liter−1, 132.8% higher than the double gene knockout mutant and 14.4% higher than the wild-type strain ATCC 31461). In addition, a new gellan gum recovery method based on the new mutant strain was investigated, in which only 30% isopropanol was required, which is twice for the wild-type strains, and the performance of the final product was improved. Thus, the mutant strain could be an ideal strain for the commercial production of gellan. IMPORTANCE A carotenoid- and PHB-free double gene knockout strain mutant was constructed to simplify the purification steps normally involved in gellan production. However, the production of gellan gum was unexpectedly reduced. A mutant with 14.4% higher gellan production than that of the wild-type strain was obtained and isolated after employing UV and EMS combined mutagenesis. Based on this high-yield and low-impurity-producing mutant, a new recovery method requiring less organic solvent and fewer operating steps was developed. This method will effectively reduce the production costs and improve the economic benefits of large-scale gellan production.

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“…Sphingomonas sanxanigenens NX02 was a wildtype strain that could coproduce the polysaccharide Sanxan and poly(R)-3-hydroxybutyrate (PHB) through the co-utilisation of glucose and xylose (Figure 1) (Wu et al, 2016(Wu et al, , 2021. After the markerless knockout of six crucial PHB biosynthetic gene phbB copies and non-rational plasma mutagenesis, a PHB-defective mutant NXdP was obtained (Wu et al, 2018). Based on strain NXdP, five genes for Sanxan synthesis were deleted to construct a chassis strain that could not produce the exopolysaccharide Sanxan, named NXdPE (Figure 1).…”

Section: Construction Of a Chassis Strain Nxdpe That Co-utilised Gluc...mentioning

confidence: 99%

The production of ultrahigh molecular weight xanthan gum from a Sphingomonas chassis capable of co‐utilising glucose and xylose from corn straw

Wu,

Shi,

Ming

et al. 2024

Microbial Biotechnology

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Corn straw is an abundant and renewable alternative for microbial biopolymer production. In this paper, an engineered Sphingomonas sanxanigenens NXG‐P916 capable of co‐utilising glucose and xylose from corn straw total hydrolysate to produce xanthan gum was constructed. This strain was obtained by introducing the xanthan gum synthetic operon gum as a module into the genome of the constructed chassis strain NXdPE that could mass produce activated precursors of polysaccharide, and in which the transcriptional levels of gum genes were optimised by screening for a more appropriate promoter, P916. As a result, strain NXG‐P916 produced 9.48 ± 0.34 g of xanthan gum per kg of fermentation broth (g/kg) when glucose was used as a carbon source, which was 2.1 times improved over the original engineering strain NXdPE::gum. Furthermore, in batch fermentation, 12.72 ± 0.75 g/kg xanthan gum was produced from the corn straw total hydrolysate containing both glucose and xylose, and the producing xanthan gum showed an ultrahigh molecular weight (UHMW) of 6.04 × 107 Da, which was increased by 15.8 times. Therefore, the great potential of producing UHMW xanthan gum by Sphingomonas sanxanigenens was proved, and the chassis NXdPE has the prospect of becoming an attractive platform organism producing polysaccharides derived from biomass hydrolysates.

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Enhancement of transparent hydrogel sanxan production in Sphingomonas sanxanigenens NX02 via rational and random gene manipulation

Cited by 6 publications

References 27 publications

Co-utilization of glucose and xylose for the production of poly-β-hydroxybutyrate (PHB) by Sphingomonas sanxanigenens NX02

Co-utilization of glucose and xylose for the production of poly-β-hydroxybutyrate (PHB) by Sphingomonas sanxanigenens NX02

A Carotenoid- and Poly-β-Hydroxybutyrate-Free Mutant Strain of Sphingomonas elodea ATCC 31461 for the Commercial Production of Gellan

The production of ultrahigh molecular weight xanthan gum from a Sphingomonas chassis capable of co‐utilising glucose and xylose from corn straw

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