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

Biochemical characterization of a recombinant laccase from Halalkalibacterium halodurans C-125 and its application in the biotransformation of organic compounds

OBJECTIVES

This study aimed to produce an engineered recombinant laccase from extremophilic Halalkalibacterium halodurans C-125 (Lac-HhC-125) with higher protein yield, into a more active conformation and with properties that meet the fundamental needs of biotechnological application.

RESULTS

The rLac-HhC125 was partially purified by size exclusion chromatography and concentrated by ultrafiltration (10 kDa) with a yield of 57.6%. Oxidation reactions showed that adding 2 mM CuSO4 to the assay solution led to activating the laccase. To increase its initial activity, the rLac-HhC125 was treated at 50 °C for 20 min before the assays, improving its performance by fourfold using the syringaldazine as a substrate. When treated with EDTA, methanol, ethanol, and DMSO, the rLac-HhC125 maintained more than 80% of its original activity. Interestingly, the acetonitrile induced a twofold activity of the rLac-HhC125. The putative rLac-HhC125 demonstrated a capability of efficient transformation of different organic compounds at pH 6, known as dye precursors, into coloured molecules.

CONCLUSION

The rLac-HhC125 was active at high temperatures and alkaline pH, exhibited tolerance to organic solvents, and efficiently transformed different hydroxy derivatives into coloured compounds, which indicates that it can be used in various biotechnological processes.

Komagataella phaffii as a Platform for Heterologous Expression of Enzymes Used for Industry

In the 1980s, Escherichia coli was the preferred host for heterologous protein expression owing to its capacity for rapid growth in complex media; well-studied genetics; rapid and direct transformation with foreign DNA; and easily scalable fermentation. Despite the relative ease of use of E. coli for achieving the high expression of many recombinant proteins, for some proteins, e.g., membrane proteins or proteins of eukaryotic origin, this approach can be rather ineffective. Another microorganism long-used and popular as an expression system is baker's yeast, Saccharomyces cerevisiae. In spite of a number of obvious advantages of these yeasts as host cells, there are some limitations on their use as expression systems, for example, inefficient secretion, misfolding, hyperglycosylation, and aberrant proteolytic processing of proteins. Over the past decade, nontraditional yeast species have been adapted to the role of alternative hosts for the production of recombinant proteins, e.g., Komagataella phaffii, Yarrowia lipolytica, and Schizosaccharomyces pombe. These yeast species' several physiological characteristics (that are different from those of S. cerevisiae), such as faster growth on cheap carbon sources and higher secretion capacity, make them practical alternative hosts for biotechnological purposes. Currently, the K. phaffii-based expression system is one of the most popular for the production of heterologous proteins. Along with the low secretion of endogenous proteins, K. phaffii efficiently produces and secretes heterologous proteins in high yields, thereby reducing the cost of purifying the latter. This review will discuss practical approaches and technological solutions for the efficient expression of recombinant proteins in K. phaffii, mainly based on the example of enzymes used for the feed industry.

Expression and Characterization of Laccase Lac1 from Coriolopsis trogii Strain Mafic-2001 in Pichia pastoris and Its Degradation of Lignin

The laccase gene (Lac1) was cloned from Coriolopsis trogii strain Mafic-2001. Full-length sequence of Lac1 containing 11 exons and 10 introns is composed of 2140 nucleotides (nts). mRNA of Lac1 encoded for a protein of 517 aa. Nucleotide sequence of the laccase was optimized and expressed in Pichia pastoris X-33. SDS-PAGE analysis showed that the molecular weight of the purified recombinant laccase rLac1 was about 70 kDa. The optimum temperature and pH of rLac1 were 40 ℃ and 3.0, respectively. rLac1 showed high residual activity (90%) in the solutions after 1 h incubation at the pH ranging from 2.5 to 8.0. rLac1 maintained over 60% of laccase activity at the temperatures ranging from 20 to 60 °C, and kept higher than 50% of its activity at 40 °C for 2 h. The activity of rLac1 was promoted by Cu2+ and inhibited by Fe2+. Under optimal conditions, lignin degradation rates of rLac1 on the substrates of rice straw, corn stover, and palm kernel cake were 50.24%, 55.49%, and 24.43% (the lignin contents of substrates untreated with rLac1 were 100%), respectively. Treated with rLac1, the structures of agricultural residues (rice straw, corn stover, and palm kernel cake) were obviously loosened which was reflected by the analysis of scanning electron microscopy and Fourier transform infrared spectroscopy. Based on the specific activity of rLac1 on the degradation of lignin, rLac1 from Coriolopsis trogii strain Mafic-2001 has the potential for in-depth utilization of agricultural residues.

Enhancing the expression of recombinant small laccase in Pichia pastoris by a double promoter system and application in antibiotics degradation

Low-expression levels remain a challenge in the quest to use the small laccase (rSLAC) as a viable catalyst. In this study, a recombinant Pichia pastoris strain (rSLAC-GAP-AOX) producing rSLAC under both AOX and GAP promoters (located in two different plasmids) was generated and cultivated in the presence of methanol and mixed feed (methanol:glycerol). Induction with methanol resulted in a maximum laccase activity of 1200 U/L for rSLAC-GAP-AOX which was approximately 2.4-fold higher than rSLAC-AOX and 5.1-fold higher than rSLAC-GAP. The addition of methanol:glycerol in a stoichiometric ratio of 9:1 consistently improved biomass and led to a 1.5-fold increase in rSLAC production as compared to induction with methanol alone. The rSLAC removed 95% of 5 mg/L ciprofloxacin (CIP) and 99% of 100 mg/L tetracycline (TC) in the presence of a mediator. Removal of TC resulted in complete elimination of antibacterial activity while up to 48% reduction in antibacterial activity was observed when CIP was removed. Overall, the present study highlights the effectiveness of a double promoter system in enhancing SLAC production.

Recombinant laccase rPOXA 1B real-time, accelerated and molecular dynamics stability study

Background

Laccases (EC 1.10.3.2) are multi-copper oxidoreductases with great biotechnological importance due to their high oxidative potential and utility for removing synthetic dyes, oxidizing phenolic compounds, and degrading pesticides, among others.

Methods

A real-time stability study (RTS) was conducted for a year, by using enzyme concentrates from 3 batches (L1, L3, and L4). For which, five temperatures 243.15, 277.15, 298.15, 303.15, 308.15, and 313.15 K were assayed. Using RTS data and the Arrhenius equation, we calculated the rPOXA 1B accelerated stability (AS). Molecular dynamics (MD) computational study results were very close to those obtained experimentally at four different temperatures 241, 278, 298, and 314 K.

Results

In the RTS, 101.16, 115.81, 75.23, 46.09, 5.81, and 4.83% of the relative enzyme activity were recovered, at respective assayed temperatures. AS study, showed that rPOXA 1B is stable at 240.98 ± 5.38, 277.40 ± 1.32 or 297.53 ± 3.88 K; with t_1/2 values of 230.8, 46.2, and 12.6 months, respectively. Kinetic and thermodynamic parameters supported the high stability of rPOXA 1B, with an E_d value of 41.40 KJ mol^− 1, a low variation of K_M and V_max, at 240.98 ± 5.38, and 297.53 ± 3.88 K, and ∆G values showing deactivation reaction does not occur. The MD indicates that fluctuations in loop, coils or loops with hydrophilic or intermediate polarity amino acids as well as in some residues of POXA 1B 3D structure, increases with temperature; changing from three fluctuating residues at 278 K to six residues at 298 K, and nine residues at 314 K.

Conclusions

Laccase rPOXA 1B demonstrated experimentally and computationally to be a stable enzyme, with t_1/2 of 230.8, 46.2 or 12.6 months, if it is preserved impure without preservatives at temperatures of 240.98 ± 5.38, 277.40 ± 1.32 or 297.53 ± 3.88 K respectively; this study could be of great utility for large scale producers.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12896-021-00698-3.

Enzymatic treatment of phenolic pollutants by a small laccase immobilized on APTES-functionalised magnetic nanoparticles

In this study, we have successfully synthesized magnetic nanoparticles (MNPs), functionalised them by silanization and used them for the covalent immobilization of a recombinant small laccase (rSLAC) from Streptomyces coelicolor. The immobilized recombinant laccase (MNP-rSLAC) was subsequently used for the treatment of phenol, 4-chlorophenol (4-CP) and 4-fluorophenol (4-FP). The enzyme completely degraded 80 µg/mL of the selected phenolic compounds within 2 h in the presence of a natural mediator, acetosyringone. The MNP-rSLAC retained > 73% of initial activity (2,6-dimethoxyphenol as substrate) after 10 catalytic cycles and could be easily recovered from the reaction mixture by the application of magnetic field. Furthermore, immobilised rSLAC exhibited better storage stability than its free counterpart. The Michaelis constant (K_m) value for the immobilised rSLAC was higher than free rSLAC, however the maximum velocity (V_max) of the immobilised SLAC was similar to that of the free rSLAC. Growth inhibition studies using Escherichia coli showed that rSLAC-mediated treatment of phenolic compounds reduced the toxicity of phenol, 4-CP and 4-FP by 90, 60 and 55%, respectively. Interestingly, the presence of selected metal ions (Co²⁺, Cu²⁺, Mn²⁺) greatly enhanced the catalytic activity of rSLAC and MNP-rSLAC. This study indicates that immobilized small laccase (MNP-rSLAC) has potential for treating wastewater contaminated with phenolic compounds.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02854-0.

Genome-based engineering of ligninolytic enzymes in fungi

Background

Many fungi grow as saprobic organisms and obtain nutrients from a wide range of dead organic materials. Among saprobes, fungal species that grow on wood or in polluted environments have evolved prolific mechanisms for the production of degrading compounds, such as ligninolytic enzymes. These enzymes include arrays of intense redox-potential oxidoreductase, such as laccase, catalase, and peroxidases. The ability to produce ligninolytic enzymes makes a variety of fungal species suitable for application in many industries, including the production of biofuels and antibiotics, bioremediation, and biomedical application as biosensors. However, fungal ligninolytic enzymes are produced naturally in small quantities that may not meet the industrial or market demands. Over the last decade, combined synthetic biology and computational designs have yielded significant results in enhancing the synthesis of natural compounds in fungi.

Main body of the abstract

In this review, we gave insights into different protein engineering methods, including rational, semi-rational, and directed evolution approaches that have been employed to enhance the production of some important ligninolytic enzymes in fungi. We described the role of metabolic pathway engineering to optimize the synthesis of chemical compounds of interest in various fields. We highlighted synthetic biology novel techniques for biosynthetic gene cluster (BGC) activation in fungo and heterologous reconstruction of BGC in microbial cells. We also discussed in detail some recombinant ligninolytic enzymes that have been successfully enhanced and expressed in different heterologous hosts. Finally, we described recent advance in CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats)-Cas (CRISPR associated) protein systems as the most promising biotechnology for large-scale production of ligninolytic enzymes.

Short conclusion

Aggregation, expression, and regulation of ligninolytic enzymes in fungi require very complex procedures with many interfering factors. Synthetic and computational biology strategies, as explained in this review, are powerful tools that can be combined to solve these puzzles. These integrated strategies can lead to the production of enzymes with special abilities, such as wide substrate specifications, thermo-stability, tolerance to long time storage, and stability in different substrate conditions, such as pH and nutrients.

Expression of Pleurotus ostreatus Laccase Gene in Pichia pastoris and Its Degradation of Corn Stover Lignin

Pleurotus ostreatus is a species of white-rot fungi that effectively degrades lignin. In this study, we aimed to efficiently express the lac-2 gene of Pleurotus ostreatus in the Pichia pastoris X33 yeast strain. The enzymatic properties of recombinant yeast were determined, and its ability to degrade corn stover lignin was determined. The results showed the optimum pH values of recombinant laccase for 2,2’-Azinobis-3-ethylbenzothiazoline-6-sulfonic acid, 2,6-dimethoxyphenol, and 2-methoxyphenol were 3.0, 3.0, and 3.5, respectively. The optimum reaction temperature was 50 °C, and it had good thermal stability and acid and alkali resistance. The degradation rate of lignin in corn stover by recombinant laccase was 18.36%, and the native Pleurotus ostreatus degradation rate was 14.05%, the difference between them is significant (p < 0.05). This experiment lays a foundation for the study of the degradation mechanism of lignin by laccase.

Preparation of Gallic Acid-Grafted Chitosan Using Recombinant Bacterial Laccase and Its Application in Chilled Meat Preservation

To improve the antibacterial and antioxidant properties of chitosan (CS), CS grafted with gallic acid (GA) using recombinant bacterial laccase from Bacillus vallismortis fmb-103 (fmb-rL103) as a catalyst. The structures of grafted chitosans were identified using Fourier transform infrared spectroscopy (FT-IR) and UV visible spectrum (UV–Vis spectroscopy). After gallic acid grafting, the antibacterial properties of chitosans against Pseudomonas, Acinetobacter, Brochothrix thermosphacta, Escherichia coli, Staphylococcus aureus, Salmonella, and Listeria monocytogenes were significantly improved. Meanwhile, 1,1-Diphenyl-2-picrylhydrazyl (DPPH) radical scavenging results showed that the antioxidant properties of grafted CS increased as well. The preservative effects of the grafted chitosan on chilled meat were then investigated. For this purpose, the quality indexes of the chilled meat during the storage were monitored, including total bacterial count, total basic volatile nitrogen (TVB-N) content, pH value, color and thiobarbituric acid reactive substances (TBARS) and so on. The results showed that coating with the grafted chitosan retarded the growth of spoilage bacteria, and decreased TVB-N and TBARS values of meat. The shelf life of chilled meat coated by CS grafted with GA (GA-g-CS) also extended from 6 days to 18 days at 4°C. These results provided a theoretical basis for the future application of the GA-g-CS in the preservation of chilled meat.

Highlights:(1)

The temperature and pH-stable bacterial laccase was used to synthesize gallic acid grafted chitosan.

(2)

Antioxidant and antibacterial properties of chitosan were improved through grafting gallic acid.

(3)

Storage properties of chilled meat were improved by coating with gallic acid grafted chitosan.