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L-glutamate oxidase (GLOD) and L-amino acid oxidase (AAO) were reported to be capable of convert L-glutamic acid to α-aketoglutaric acid (α-KG). These two enzymes gene have been successfully expressed by using pHBM905BDM in Pichia pastoris to produce α-aketoglutaric acid from L-glutamic acid in our previous studies. Here these two enzymes were displayed on P. pastoris to achieve the conversion. We constructed multi-copy expression plasmids using plasmid pHBM905BDM. By using this plasmid, multi-copy strains were constructed and named as PGLOD(1–3)-AGα1 and PAAO(1–3)-AGα1, respectively. The following results showed that expression of GLOD(1–3)-AGα1 and AAO(1–3)-AGα1 in multi-copy strains increased as designed and strain PGLOD3-AGα1 and PAAO3-AGα1 was chosen for high-density fermentation and enzyme activity experiments. By using a multi-copy expression approach and high-density fermentation, we achieved a GLOD expression yield of 688.5 U/g dry cell weight and AAO expression yield of 626.7 U/g dry cell weight. By using displayed GLOD, the average production rate of L-glutamic acid to α-KG was 6.22 g/L/h and the highest α-KG titer (124.5 g/L) was converted from 135 g/L L-glutamic acid. By using displayed AAO, the average production rate of L-glutamic acid to α-KG was 5.78 g/L/h and the highest α-KG titer (115.6 g/L) was converted from 135 g/L L-glutamic acid. It showed that displaying enzymes on P. pastoris are suitable for use in industrial applications.

Chitin is a linear homopolymer of acetylated β-(1,4)-linked glucosamine residues and among the most abundant polysaccharides in the world. Here, we identified and purified a novel chitosanase (CCHA) from Aspergillus oryzae NKY2017 obtained from Hu’bei province in China. Construction of a cDNA library from this strain revealed the gene sequence subsequently expressed in Pichia pastoris and subsequent construction of multi-copy expression plasmids (CCHA1/2/3/4). The results demonstrated elevated levels of CCHA expression in multi-copy strains, with strain CCHA4 chosen for high-density fermentation and enzyme-activity experiments. High-density fermentation achieved a CCHA yield of 22,500 U/mL, and temperature and pH optimization resulted in the highest CCHA activity at 40°C and 4.0, respectively. We used this enzyme for a large-scale preparation of oligosaccharides: 4 g enzyme could convert 150 kg chitosan into oligosaccharides in 24 h at 40°C. These results demonstrated abundant CCHA expression in P. pastoris and suggested the efficacy of CCHA for use in industrial applications.

Additional file 1: Consent informed and Supplementary methods

Additional file 3: Fig. S1. Gradual recovery of the oral microbiome. Fig. S2. Noninvasive prediction model for CPR1 neutralizing antibodies based on the oral microbiome. Fig. S3. Gradual recovery of the gut microbiome. Fig. S4. Noninvasive prediction model for CPR1 neutralizing antibodies based on the gut microbiome. Fig. S5. Correlation between 204 different metabolites from CPR1 and CPR0 was identified. Fig. S6. Correlation between 216 different metabolites from CPR1 and HC was figured out. Fig. S7. Noninvasive prediction model for CPR1 neutralizing antibodies based on plasma metabolomics. Fig. S8. Correlation in gut and oral microbiome and plasma metabonomics and clinical indicators between CPR1 and HC.

L-amino acid oxidase (AAO) was reported to be capable of converting L-glutamic acid to α-aketoglutaric acid (α-KG). The sequence of AAO from Kitasatospora cheerisanensis was synthesized based on Pichia pastoris codon-usage preferences. AAO gene was cloned into plasmid pPICZα which was transformed into P. pastoris. Next, multi-copy expression plasmids were constructed by using plasmid pHBM905BDM. High-density fermentation was performed and the recombinant enzyme was characterized. The conversion conditions were optimized. By using Escherichia coli expression system, no soluble or active AAO was obtained from two strains after fermentation and induction. We can’t obtain high-level expression of recombinant strains by using plasmid pPICZα. Therefore, we constructed multi-copy expression plasmids using plasmid pHBM905BDM. By using this plasmid, multi-copy strains were constructed and named as PAAO1, PAAO2, PAAO3, PAAO4, and PAAO5, respectively. The following results showed that expression of AAO in multicopy strains increased as designed and strain PAAO5 was chosen for high-density fermentation and enzyme activity experiments. After high-density fermentation, we achieved an AAO-expression yield of 120.8 U/mL. After temperature and pH optimization, the highest AAO activity was observed at a temperature and pH of 20°C and 6, respectively. After optimization of the conversion conditions, the average production rate of L-glutamic acid to α-KG was 3.46 g/L/h and the highest α-KG titer (103 g/L) was converted from 120 g/L L-glutamic acid. In this study, AAO was abundantly expressed by using P. pastoris expression system. The following experiments indicated that AAO is suitable for use in industrial applications.

An auto-inducing expression system was developed that could express target genes in S. marcescens MG1. Using this system, MG1 was constructed as a whole-cell biocatalyst to produce 2,3-butanediol/acetoin. Formate dehydrogenase (FDH) and 2,3-butanediol dehydrogenase were expressed together to build an NADH regeneration system to transform diacetyl to 2,3-butanediol. After fermentation, the extract of recombinant S. marcescens MG1ABC (pETDuet-bdhA-fdh) showed 2,3-BDH activity of 57.8 U/mg and FDH activity of 0.5 U/mg. And 27.95 g/L of 2,3-BD was achieved with a productivity of 4.66 g/Lh using engineered S. marcescens MG1(Pswnb+pETDuet-bdhA-fdh) after 6 h incubation. Next, to produce 2,3-butanediol from acetoin, NADH oxidase and 2,3-butanediol dehydrogenase from Bacillus subtilis were co-expressed to obtain a NAD+ regeneration system. After fermentation, the recombinant strain S. marcescens MG1ABC (pSWNB+pETDuet-bdhA-yodC) showed AR activity of 212.4 U/mg and NOX activity of 150.1 U/mg. We obtained 44.9 g/L of acetoin with a productivity of 3.74 g/Lh using S. marcescens MG1ABC (pSWNB+pETDuet-bdhA-yodC). This work confirmed that S. marcescens could be designed as a whole-cell biocatalyst for 2,3-butanediol and acetoin production.

Background DNA polymerases are important enzymes that synthesize DNA molecules and therefore are critical to various scientific fields as essential components of in vitro DNA synthesis reactions, including PCR. Modern diagnostics, molecular biology, and genetic engineering require DNA polymerases with improved performance. This study aimed to obtain and characterize a new CL7-Taq fusion DNA polymerase, in which the DNA coding sequence of Taq DNA polymerase was fused with that of CL7, a double-stranded DNA binding-like protein from Escherichia coli. Results The resulting novel recombinant gene was cloned and expressed in E. coli. The recombinant CL7-Taq protein exhibited excellent thermostability, extension rate, sensitivity, and resistance to PCR inhibitors. Our results showed that the sensitivity of CL7-Taq DNA polymerase was 100-fold higher than that of wild-type Taq, which required a template concentration of at least 1.8 × 105 aM. Moreover, the extension rate of CL7-Taq was 4 kb/min, which remarkably exceeded the rate of Taq DNA polymerase (2 kb/min). Furthermore, the CL7 fusion protein showed increased resistance to inhibitors of DNA amplification, including lactoferrin, heparin, and blood. Single-cope human genomic targets were readily available from whole blood, and pretreatment to purify the template DNA was not required. Conclusions Thus, this is a novel enzyme that improved the properties of Taq DNA polymerase, and thus may have wide application in molecular biology and diagnostics.

Methyl parathion hydrolase (MPH) hydrolyses methyl parathion efficiently and specifically. Herein, we produced MPH from Plesiomonas sp. M6 using a Pichia pastoris multi-copy expression system. The original signal peptide sequence of the target gene was removed, and a modified coding sequence was synthesised. Multi-copy expression plasmids containing MPH were constructed using pHBM905BDM, and used to generate recombinant strains containing 1, 2, 3 or 4 copies of the MPH gene. The results showed that a higher target gene copy number increased the production of recombinant MPH (MPH-R), as anticipated. The expression level of the recombinant strain containing four copies of the MPH gene was increased to 1.9 U/ml using 500 ml shake flasks, and the specific activity was 15.8 U/mg. High-density fermentation further increased the target protein yield to 18.4 U/ml. Several metal ions were tested as additives, and Ni2+, Co2+ and Mg2+ at a concentration of 1 mM enhanced MPH-R activity by 196%, 201% and 154%, respectively. Enzyme immobilisation was then applied to overcome the difficulties in recovery, recycling and long-term stability associated with the free enzyme. Immobilised MPH-R exhibited significantly enhanced thermal and long-term stability, as well as broad pH adaptability. In the presence of inhibitors and chelating agents such as sodium dodecyl sulphate (SDS), immobilised MPH-R displayed 2-fold higher activity than free MPH-R, demonstrating its potential for industrial application.

l-glutamate oxidase (GLOD), encoded by the gox gene, catalyses the transformation of l-glutamic acid into α-ketoglutaric acid (α-KG). In the present study, Pichia pastoris was used for heterologous production of GLOD following optimization of the gox coding sequence for expression in the yeast host. A series of constructs based on the pHBM905BDM plasmid were engineered and transformed into P. pastoris to increase the gox copy number. The results indicated that GLOD protein levels and enzyme activity increased with increasing gox copy number. Strain PGLOD4, which contained four copies of the target gene, was chosen for subsequent fermentation experiments, and a fermentation strategy involving two exponential feeding phases was developed. During the preinduction phase, glycerol was fed exponentially at μG = 0.15/h. When the cell density reached 300 g/l, methanol was fed exponentially at μM = 0.03/h to induce GLOD production. After 84 h of cultivation, the final cell density and total enzyme activity reached 420 g/L and 247.8 U/mL, respectively. The recombinant enzyme displayed an optimum temperature of 40 °C, which was higher than recombinant enzyme expressed in E. coli. This is important because increasing the temperature could accelerate enzymatic transformation of l-glutamic acid to α-KG. Experiments also demonstrated superior thermo-stability for the enzyme produced in yeast, which further enhances its potential for industrial applications.

An artificial network which can accomplish recombinant protein synthesis guided by cell population in E. coli was constructed. The successful functioning of this network requires two plasmids, pWNB and pET. pWNB is responsible for production of T7 RNA polymerase, which controls pET; pET, in turn, regulates the production of target proteins. Several model proteins were tested and the results show that this E. coli system can be used to efficiently express various recombinant proteins. Since system contains T7 RNA polymerase production elements, it is transferable and applicable to well-characterized E. coli strains. Compared to the IPTG-induced system, an equal or greater amount of target protein can be obtained using this auto-inducible expression system in flasks and bioreactors. Our results suggest that it is a competitive alternative to other expression systems used in labs or for industrial applications.

Bacillus vallismortis NBIF-001, a Gram-positive bacterium, was isolated from soil in Shangri-La, China. Here, we provide the complete genome sequence of this bacterium, which has a 3,929,787-bp-long genome, including 4,030 protein-coding genes and 195 RNA genes. This strain possesses a number of genes encoding virulence factors of pathogens.

Two thermophilic β-mannanases (ManA and ManB)were successfully expressed in Yarrowialipolytica using vector pINA1296I. The sequences of manA from Aspergillus niger CBS 513.88 and manB from Bacillus subtilis BCC41051 were optimized based on codon-usage bias in Y.lipolytica and synthesized by overlapping polymerase chain reaction (PCR). We utilized the pINA1296I vector, which allows inserting and expression of multiple copies of an expression cassette, to engineer recombinant strains containing multiple copies of manA or manB. Following verification of target-gene expression by quantitative PCR, fermentation experiments indicated that recombinant protein levels and enzyme activity increased along with increasing manA/manB copy number.After production in a 10 l fermenter, we obtained maximum enzyme activity from strains YLA6 and YLB6 of3024 U/mL and 1024 U/mL, respectively. Additionally, purification and characterization results revealed that the optimum pH and temperature for manA activity were pH∼5 and ∼70 °C, and for manB activity were pH∼7 and 60 °C, respectively. These results indicated that the thermo stabilities of these two enzymes were higher than most other mannanases, making them potentially useful for industrial applications.