Extracellular expression of alkaline phytase in Pichia pastoris: Influence of signal peptides, promoters and growth medium

High-efficiency secretory expression and characterization of the recombinant type III human-like collagen in Pichia pastoris

Collagen, the highest content protein in the body, has irreplaceable biological functions, and it is widespread concerned in food, beauty, and medicine with great market demand. The gene encoding the recombinant type III human-like collagen α1 chain fragment was integrated into P. pastoris genome after partial amino acids were substituted. Combined with promoter engineering and high-density fermentation technology, soluble secretory expression with the highest yield of 1.05 g L-1 was achieved using two-stage feeding method, and the purity could reach 96% after affinity purification. The determination of N/C-terminal protein sequence were consistent with the theoretical expectation and showed the characteristics of Gly-X-Y repeated short peptide sequence. In amino acid analysis, glycine shared 27.02% and proline 23.92%, which were in accordance with the characteristics of collagen. Ultraviolet spectrum combined with Fourier transform infrared spectroscopy as well as mass spectrometry demonstrated that the target product conformed to the characteristics of collagen spectrums and existed as homologous dimer and trimer in the broth. This work provided a sustainable and economically viable source of the recombinant type III human-like collagen.

Microbial engineering for the production and application of phytases to the treatment of the toxic pollutants: A review

Phytases are a group of digestive enzymes which are commonly used as feed enzymes. These enzymes are used exogenously in the feeds of monogastric animals thereby it improves the digestibility of phosphorous and thus reduces the negative impact of inorganic P excretion on the environment. Even though these enzymes are widely distributed in many life forms, microorganisms are the most preferred and potential source of phytase. Despite the extensive availability of the phytase-producing microbial consortia, only a few microorganisms have been known to be exploited at industrial level. The high costs of the enzyme along with the incapability to survive high temperatures followed by the poor storage stability are noted to be the bottleneck in the commercialization of enzymes. For this reason, besides the conventional fermentation approaches, the applicability of cloning, expression studies and genetic engineering has been implemented for the past few years to accomplish the abovesaid benefits. The site-directed mutagenesis as well as knocking out have also validated their prominent role in microbe-based phytase production with enhanced levels. The present review provides detailed information on recent insights on the modification of phytases through heterologous expression and protein engineering to make thermostable and protease-resistant phytases.

Improved Production of Recombinant Myrosinase in Pichia pastoris

The effect of the deletion of a 57 bp native signal sequence, which transports the nascent protein through the endoplasmic reticulum membrane in plants, on improved AtTGG1 plant myrosinase production in Pichia pastoris was studied. Myrosinase was extracellularly produced in a 3-liter laboratory fermenter using α-mating factor as the secretion signal. After the deletion of the native signal sequence, both the specific productivity (164.8 U/L/h) and volumetric activity (27 U/mL) increased more than 40-fold compared to the expression of myrosinase containing its native signal sequence in combination with α-mating factor. The deletion of the native signal sequence resulted in slight changes in myrosinase properties: the optimum pH shifted from 6.5 to 7.0 and the maximal activating concentration of ascorbic acid increased from 1 mM to 1.5 mM. Kinetic parameters toward sinigrin were determined: 0.249 mM (K_m) and 435.7 U/mg (V_max). These results could be applied to the expression of other plant enzymes.

Construction of a novel MK-4 biosynthetic pathway in Pichia pastoris through heterologous expression of HsUBIAD1

Background

With a variety of physiological and pharmacological functions, menaquinone is an essential prenylated product that can be endogenously converted from phylloquinone (VK₁) or menadione (VK₃) via the expression of Homo sapiens UBIAD1 (HsUBIAD1). The methylotrophic yeast, Pichia pastoris, is an attractive expression system that has been successfully applied to the efficient expression of heterologous proteins. However, the menaquinone biosynthetic pathway has not been discovered in P. pastoris.

Results

Firstly, we constructed a novel synthetic pathway in P. pastoris for the production of menaquinone-4 (MK-4) via heterologous expression of HsUBIAD1. Then, the glyceraldehyde-3-phosphate dehydrogenase constitutive promoter (P_GAP) appeared to be mostsuitable for the expression of HsUBIAD1 for various reasons. By optimizing the expression conditions of HsUBIAD1, its yield increased by 4.37 times after incubation at pH 7.0 and 24 °C for 36 h, when compared with that under the initial conditions. We found HsUBIAD1 expressed in recombinant GGU-23 has the ability to catalyze the biosynthesis of MK-4 when using VK₁ and VK₃ as the isopentenyl acceptor. In addition, we constructed a ribosomal DNA (rDNA)-mediated multi-copy expression vector for the fusion expression of SaGGPPS and PpIDI, and the recombinant GGU-GrIG afforded higher MK-4 production, so that it was selected as the high-yield strain. Finally, the yield of MK-4 was maximized at 0.24 mg/g DCW by improving the GGPP supply when VK₃ was the isopentenyl acceptor.

Conclusions

In this study, we constructed a novel synthetic pathway in P. pastoris for the biosynthesis of the high value-added prenylated product MK-4 through heterologous expression of HsUBIAD1 and strengthened accumulation of GGPP. This approach could be further developed and accomplished for the biosynthesis of other prenylated products, which has great significance for theoretical research and industrial application.

Characteristics of a recombinant Lentinula edodes endoglucanase and its potential for application in silage of rape straw

An experiment was conducted to determine the characteristics of recombinant endoglucanase and its effects on rape straw silage. The endoglucanase from Lentinula edodes (LeCel12A) was produced in Pichia pastoris and shown maximum activity at 40 °C and pH 3.0. The LeCel12A exhibited preferential hydrolysis of carboxymethylcellulose. The activity of LeCel12A could be enhanced by MnCl₂ in dose-dependent manners. Trp22 was a key amino acid affecting LeCel12A activity. The LeCel12A enhanced the hydrolysis of rape straw, rice straw, wheat straw, and corn straw. Supplemental LeCel12A increased lactic acid concentration and reduced lignocellulosic content of the rape straw silage. Though an increase in the saccharification efficiency of LeCel12A-treated rape straw silage was observed when the fibrolytic enzyme loading of hydrolysis system was enough, supplemental LeCel12A did not dramatically enhance the saccharification of rape straw silage in the current study. This study demonstrates that LeCel12A may be useful for improving the utilization of rape straw silage as an additive, but its supplemental dose, cost benefit, and consequent application possibility in biofuel production require careful consideration and further investigation.

Expression of a Recombinant Lentinula edodes Xylanase by Pichia pastoris and Its Effects on Ruminal Fermentation and Microbial Community in in vitro Incubation of Agricultural Straws

Agricultural straws, such as rice straw, wheat straw, and corn straw, are produced abundantly every year but not utilized efficiently in China. An experiment was conducted to determine the effects of recombinant xylanase on ruminal fermentation and microbial community structure in in vitro incubation of these straws. The recombinant xylanase from Lentinula edodes (rLeXyn11A) was produced in Pichia pastoris. The optimal temperature and pH for rLeXyn11A were 40°C and 4.0, respectively. The rLeXyn11A featured resistance to high temperature and showed broad temperature adaptability (>50% of the maximum activity at 20-80°C). Supplemental rLeXyn11A enhanced the hydrolysis of three agricultural straws. After in vitro ruminal incubation, regardless of agricultural straws, the fiber digestibility, acetate concentration, total volatile fatty acids (VFAs) production, and fermentation liquid microbial protein were increased by rLeXyn11A. Supplemental rLeXyn11A increased the ammonia-N concentration for corn straw and rice straw. High throughput sequencing and real-time PCR data showed that the effects of rLeXyn11A on ruminal microbial community depended on the fermentation substrates. With rice straw, rLeXyn11A increased the relative abundance of fibrolytic bacteria including Firmicutes, Desulfovibrio, Ruminococcaceae and its some genus, and Fibrobacter succinogenes. With wheat straw, rLeXyn11A increased the relative abundance of Ruminococcus_1 and its three representative species F. succinogenes, Ruminococcus flavefaciens, Ruminococcus albus. With corn straw, the fibrolytic bacteria Firmicutes, Christensenellaceae_R_7_group, Saccharofermentans, and Desulfovibrio were increased by rLeXyn11A. This study demonstrates that rLeXyn11A could enhance in vitro ruminal digestion and fermentation of agricultural straws, showing the potential of rLeXyn11A for improving the utilization of agricultural straws in ruminants.

Secretory expression of recombinant small laccase from Streptomyces coelicolor A3(2) in Pichia pastoris

This work reports for the first time the secretory expression of the small laccase (SLAC) from Streptomyces coelicolor A3(2) in Pichia pastoris. Using an AOX1 promoter and α factor as a secretion signal, the recombinant P. pastoris harbouring the laccase gene (rSLAC) produced high titres of extracellular laccase (500 ± 10 U/l), which were further increased seven fold by pre-incubation at 80 °C for 30 min. The enzyme (∼38 kDa) had an optimum activity at 80 °C, but optimum pH varied with substrate used. K_m values for ABTS, SGZ and 2,6-DMP were 142.85 μM, 10 μM and 54.55 μM and the corresponding k_cat values were 60.6 s^-1, 25.36 s^-1 and 27.84 s^-1, respectively. The t_1/2 values of the rSLAC at 60 °C, 70 °C, 80 °C were 60 h, 32 h and 10 h, respectively. The enzyme deactivation energy (E_d) was 117.275 kJ/mol while ΔG, ΔH and ΔS for thermal inactivation of the rSLAC were all positive. The rSLAC decolourised more than 90% of Brilliant Blue G and Trypan Blue dye in 6 h without the addition of a mediator. High titres of SLAC expressed in P. pastoris enhance its potential for various industrial applications.

Microbial phytase: Impact of advances in genetic engineering in revolutionizing its properties and applications

Phytases are enzymes that increase the availability of phosphorous in monogastric diet and reduces the anti-nutrition effect of phytate. This review highlights contributions of recombinant technology to phytase research during the last decade with specific emphasis on new generation phytases. Application of modern molecular tools and genetic engineering have aided the discovery of novel phytase genes, facilitated its commercial production and expanded its applications. In future, by adopting most recent gene improvement techniques, more efficient next generation phytases can be developed for specific applications.

Engineering strategies for enhanced production of protein and bio-products in Pichia pastoris: A review

Pichia pastoris has been recognized as one of the most industrially important hosts for heterologous protein production. Despite its high protein productivity, the optimization of P. pastoris cultivation is still imperative due to strain- and product-specific challenges such as promoter strength, methanol utilization type and oxygen demand. To address the issues, strategies involving genetic and process engineering have been employed. Optimization of codon usage and gene dosage, as well as engineering of promoters, protein secretion pathways and methanol metabolic pathways have proved beneficial to innate protein expression levels. Large-scale production of proteins via high cell density fermentation additionally relies on the optimization of process parameters including methanol feed rate, induction temperature and specific growth rate. Recent progress related to the enhanced production of proteins in P. pastoris via various genetic engineering and cultivation strategies are reviewed. Insight into the regulation of the P. pastoris alcohol oxidase 1 (AOX1) promoter and the development of methanol-free systems are highlighted. Novel cultivation strategies such as mixed substrate feeding are discussed. Recent advances regarding substrate and product monitoring techniques are also summarized. Application of P. pastoris to the production of biodiesel and other value-added products via metabolic engineering are also reviewed. P. pastoris is becoming an indispensable platform through the use of these combined engineering strategies.

Potential of Pichia pastoris for the production of industrial penicillin G acylase

This study deals with the potential of Pichia pastoris X-33 for the production of penicillin G acylase (PGA^A) from Achromobacter sp. CCM 4824. Synthetic gene matching the codon usage of P. pastoris was designed for intracellular and secretion-based production strategies and cloned into vectors pPICZ and pPICZα under the control of AOX1 promoter. The simple method was developed to screen Pichia transformants with the intracellularly produced enzyme. The positive correlation between acylase production and pga gene dosage for both expression systems was demonstrated in small scale experiments. In fed-batch bioreactor cultures of X-33/PENS2, an extracellular expression system, total PGA^A expressed from five copies reached 14,880 U/L of an active enzyme after 142 h; however, 60% of this amount retained in the cytosol. The maximum PGA^A production of 31,000 U/L was achieved intracellularly from nine integrated gene copies of X-33/PINS2 after 90 h under methanol induction. The results indicate that in both expression systems the production level of PGA^A is similar but there is a limitation in secretion efficiency.