Efficient secretory overexpression of Bacillus subtilis pectate lyase in Escherichia coli and single-step purification

Efficient Secretory Overexpression of Endoinulinase in Escherichia coli and the Production of Inulooligosaccharides

Endoinulinase production was achieved by heteroexpression of endoinulinase-encoding gene from Aspergillus ficuum which is an eukaryotic organism in Escherichia coli BL21 (DE3). Further analysis demonstrated that the native signal peptide existed in inu2 gene lowered the enzyme expression level. To realize extracellular accumulation of target protein and improve its expression level, native signal peptide was substituted with pelB, ompC, and pelB fusing with the native signal peptides; then, the effects on endoinulinase production were investigated. As a result, E. coli A606-3, with replacement of pelB as its signal peptide, showed the highest endoinulinase enzyme activity (75.22 U/mg). Also, it suggested that eukaryotic signal peptides have an inhibition on enzyme expression in prokaryotic organism. Moreover, the condition for inulooligosaccharide (IOS) production from inulin was optimized, and an IOS yield of 94.41 % was achieved under the condition of 15 % (w/v) inulin, purified endoinulinase dosage of 5 U/g inulin, 55 °C, and pH 4.6 for 24 h. The major products of hydrolysis of inulin were identified as DP3 to DP7.

A Novel Thermophilic Pectate Lyase Containing Two Catalytic Modules ofClostridium stercorarium

The Clostridium stercorarium F-9 pel9A gene encodes a pectate lyase Pel9A consisting of 1,240 amino acids with a molecular weight of 135,171. The mature form of Pel9A is a modular enzyme composed of two family-9 catalytic modules of polysaccharide lyases, CM9-1 and CM9-2, in order from the N terminus. Pel9A showed an overall sequence similarity to the hypothetical pectate lyase PelX of Bacillus halodurans (sequence identity 53%), and CM9-2 showed moderate sequence similarities to some pectate lyases of family 9. Sequence identity between CM9-1 and CM9-2 was 21.3%. The full-length Pel9A lacking the N-terminal signal peptide was expressed, purified, and characterized. The enzyme required Ca(2+) ion for its enzyme activity and showed high activity toward polygalacturonic acid but lower activity toward pectin, indicating that Pel9A is a pectate lyase. Immunological analysis using an antiserum raised against the purified enzyme indicated that Pel9A is constitutively synthesized by C. stercorarium F-9.

Enhancing production of alkaline polygalacturonate lyase from Bacillus subtilis by fed-batch fermentation

Alkaline polygalacturonate lyase (PGL, EC 4.2.2.2) is an enzyme used in many industries. We developed a fed-batch fermentation process that combines the enzymatic pretreatment of the carbon source with controlling the pH of the fermentative broth to enhance the PGL production from Bacillus subtilis 7-3-3 to decrease the production cost. Maintaining the fermentation broth at pH 6.5 prior to feeding with ammonia and at pH 6.0 after feeding significantly improved PGL activity (743.5 U mL-1) compared with the control (202.5 U mL-1). The average PGL productivity reached 19.6 U mL-1 h-1 after 38 h of fermentation. The crude PGL was suitable for environmentally friendly ramie enzymatic degumming.

High-level extracellular production of alkaline polygalacturonate lyase in Bacillus subtilis with optimized regulatory elements

The present work aims to construct a robust recombinant Bacillus subtilis to achieve secretory production of alkaline polygalacturonate lyase (PGL). First, 6 signal peptides (amyX, bpr, vpr, yvgO, wapA and nprE) were screened with a semi-rational approach and comparatively investigated their effects on the production of PGL. The signal peptide bpr directed efficient PGL secretory expression and increased PGL titer to 313.7 U mL(-1). By optimizing and applying strong promoter P43 and Shine-Dalgarno sequence, higher titer of 446.3 U mL(-1) PGL was achieved. Finally, the capacity of the recombinant B. subtilis WB43CB was evaluated with a fed-batch strategy in 3 L fermentor. The PGL titer reached 632.6 U mL(-1) with a productivity of 17.6 U mL(-1) h(-1), which was the highest secretory production of PGL by the B. subtilis system. The recombinant B. subtilis strain WB43CB constructed in the present work has great potential in production of alkaline PGL.

High-level extracellular production of D-Psicose-3-epimerase with recombinant Escherichia coli by a two-stage glycerol feeding approach

The aim of this study is to achieve high-level extracellular production of D-Psicose-3-epimerase (DPE) with recombinant Escherichia coli. High-level production of DPE is one of the key factors in D-Psicose production. In the present study, the gene AAL45544.1 from Agrobacterium tumefaciens str. C58 was modified by artificial synthesis for overexpression in E. coli. The total DPE activity reached 3.96 U mL(-1) after optimization of the media composition, induction temperature, and concentration of inducer. Furthermore, it was found that addition of glycine had a positive effect on the extracellular production of DPE, which reached 3.5 U mL(-1). Finally, a two-stage glycerol feeding strategy based on both the specific growth rate before induction and the amount of glycerol residues after induction was applied in a 3-L fermenter. After a series of optimal strategies in the 3-L fermenter, the total and extracellular DPE activity were 5.08- and 3.11-fold higher than that noted in the shake flask. The extracellular and intracellular DPE activity reached 10.9 and 13.2 U mL(-1), achieving 25.5 and 31.1 % conversion of D-fructose to D-psicose, respectively. The systemic strategies presented in this study provide valuable novel information for the industrial application of DPE.

Overproduction of alkaline polygalacturonate lyase in recombinant Escherichia coli by a two-stage glycerol feeding approach

This work aims to achieve the overproduction of alkaline polygalacturonate lyase (PGL) with recombinant Escherichia coli by a two-stage glycerol feeding approach. First, the PGL coding gene from Bacillus subtilis WSHB04-02 was expressed in E. coli BL21 (DE3) under the strong inducible T7 promoter of the pET20b (+) vector. And then the influence of media composition, induction temperature, and inducer isopropyl β-D-1-thiogalactopyranoside (IPTG) concentration on cell growth and PGL production was investigated. Finally, a two-stage glycerol feeding strategy was proposed and applied in a 3-L fermenter, where cultivation was conducted at a controlled specific growth rate (μset=0.2) during pre-induction phase, followed by a constant glycerol feeding rate of 12 ml h(-1) at post-induction phase. The total PGL yield reached 371.86 U mL(-1), which is the highest PGL production by recombinant E. coli expression system.

Signal peptide of Aureobasidium pullulans xylanase: use for extracellular production of a fungal xylanase by Escherichia coli

An extracellular xylanase XynI of glycoside hydrolase family 11 from the dimorphic fungus Aureobasidium pullulans ATCC 20524 possesses an N-terminal extension of 34 amino acids (Ohta et al., J. Biosci. Bioeng. 92:262-270, 2001). The N-terminal extension includes three sites (Ala-X-Ala-X-Ala-X-Ala) that are potentially cleavable by signal peptidase I of Escherichia coli. The A. pullulans xynI signal sequence was fused in frame to the mature protein region of the equivalent xylanase gene xynA from the filamentous fungus Penicillium citrinum. The gene fusion xynI::A was inserted into the plasmid pET-26b(+) to yield pEXP401. An E. coli BL21(DE3) transformant harboring the pEXP401 exhibited xylanase activity (per ml of the culture) of 16.8 U in the fraction of culture supernatant as well as 4.29 U in the fraction of cell-free extract after 12 h of growth with isopropyl-β-D-thiogalactopyranoside at 30°C. N-terminal amino acid sequence analysis of the secreted recombinant proteins revealed cleavage at four distinct sites within the N-terminal extension of XynI, two of which conformed to the Ala-X-Ala motif prior to the cleavage site. The XynA proteins secreted into the culture medium showed high specific activities from 506 to 651 U/mg, which were twofold higher than that of the native enzyme.

In silico characterization of pectate lyase protein sequences from different source organisms

A total of 121 protein sequences of pectate lyases were subjected to homology search, multiple sequence alignment, phylogenetic tree construction, and motif analysis. The phylogenetic tree constructed revealed different clusters based on different source organisms representing bacterial, fungal, plant, and nematode pectate lyases. The multiple accessions of bacterial, fungal, nematode, and plant pectate lyase protein sequences were placed closely revealing a sequence level similarity. The multiple sequence alignment of these pectate lyase protein sequences from different source organisms showed conserved regions at different stretches with maximum homology from amino acid residues 439–467, 715–816, and 829–910 which could be used for designing degenerate primers or probes specific for pectate lyases. The motif analysis revealed a conserved Pec_Lyase_C domain uniformly observed in all pectate lyases irrespective of variable sources suggesting its possible role in structural and enzymatic functions.

Enhancement of alkaline polygalacturonate lyase production in recombinant Pichia pastoris according to the ratio of methanol to cell concentration

Polygalacturonate lyase (PGL) production by Pichia pastoris GS115 was used as a model to study the mechanism and strategy for enhancing heterologous protein production. It was found that the ratio of methanol to cell concentration had a significant influence on PGL production. In this study, an advanced glycerol exponential feeding strategy was developed for biomass accumulation in cell growth phase, by which cell concentration reached 140 g L(-1) after 19 h glycerol feeding. In subsequent production phase, a methanol feeding profile was proposed according to the optimal ratio of methanol to cell concentration at a range of 0.163-0.171 g g(-1), and PGL activity and productivity reached 430 U mL(-1) and 4.34 U mL(-1)h(-1), respectively. The strategy for enhancing PGL production by controlling the optimal ratio may provide an alternative approach to enhance heterologous protein production with P. pastoris.

Heterologous expression, secretion and characterization of the Geobacillus thermoleovorans US105 type I pullulanase

Pullulanase type I of Geobacillus thermoleovorans US105 strain (PUL US105) was produced and secreted efficiently in the E. coli periplasmic or extracellular fraction using two different signal peptides. Hence, the open reading frame was connected downstream of the lipase A signal peptide of Bacillus subtilis strain leading to an efficient secretion of an active form enzyme on the periplasmic fraction. In addition, pul US105 was fused to the alpha-amylase signal sequence of the Bacillus stearothermophilus US100 strain. The monitoring of the pullulanase activity and Western blot analysis for this last construction showed that the most activity was found in the supernatant culture, proving the efficient secretion of this natively cytoplasmic enzyme as an active form. The PUL US105 was purified to homogeneity from the periplasmic fraction, using heat treatment, size exclusion, and anion-exchange chromatography. The native pullulanase has a molecular mass of 160 kDa and is composed of two identical subunits of 80 kDa each. It was independent for metallic ions for its activity, while its thermostability was obviously improved in presence of only 0.1 mM CaCl2.

Efficient secretory expression of an alkaline pectate lyase gene from Bacillus subtilis in E. coli and the purification and characterization of the protein

The gene encoding pectate lyase (PL) from Bacillus subtilis WSHB04-02 was amplified by PCR, fused with a periplasmic secretion signal peptide sequence, pelB, from pET22b(+), cloned and expressed in Escherichia coli cells using a temperature control vector, pHsh. The recombinant E. coil was grown in a 5 l fermentor. PL was secreted in broth at 22 U l(-1) after 20 h when temperature was increased from 30 degrees C to 42 degrees C. The recombinant enzyme was purified to homogeneity as judged by SDS-PAGE. It was optimally active at pH 9.4 and 50 degrees C over 30 min. Analysis of polygalacturonic acid (PGA) degradation products by electrospray ionization (ESI)-mass spectrometry (MS) indicated that PL produced a mixture of unsaturated oligo-galacturonides including unsaturated tri-galacturonic acid and unsaturated bi-galacturonic acid but not unsaturated mono-galacturonic acid.

Microbial pectic transeliminases

Pectic transeliminases, also known as pectic lyases or pectinases, are involved in the degradation of pectic substances. They have a wide range of applications in food and textile processing. Although Aspergillus and Penicillium spp. produce pectin lyases, bacteria are the major producers of polygalacturonate lyase. The yields of pectic transeliminases are less than other pectinases. Since new applications for pectic transeliminases are emerging, an improved process for the production of these enzymes is necessary.