Engineered thermostable microbial enzymes are widely employed to catalyze chemical reactions in numerous industrial sectors. Although high thermostability is a prerequisite of industrial applications, enzyme activity is usually sacrificed during thermostability improvement. Therefore, it is vital to select the common and compatible strategies between thermostability and activity improvement to reduce mutants̕ libraries and screening time. Three functional protein engineering approaches, including directed evolution, rational design, and semi-rational design, are employed to manipulate protein structure on a genetic basis. From a structural standpoint, integrative strategies such as increasing substrate affinity; introducing electrostatic interaction; removing steric hindrance; increasing flexibility of the active site; N- and C-terminal engineering; and increasing intramolecular and intermolecular hydrophobic interactions are well-known to improve simultaneous activity and thermostability. The current review aims to analyze relevant strategies to improve thermostability and activity simultaneously to circumvent the thermostability and activity trade-off of industrial enzymes.
Heterologous functional expression of the recombinant lipases is typically a bottleneck due to the expression in the insoluble fraction as inclusion bodies (IBs) which are in inactive form. Due to the importance of lipases in various industrial applications, many investigations have been conducted to discover suitable approaches to obtain functional lipase or increase the expressed yield in the soluble fraction. The utilization of the appropriate prokaryotic and eukaryotic expression systems, along with the suitable vectors, promoters, and tags, has been recognized as a practical approach. One of the most powerful strategies to produce bioactive lipases is using the molecular chaperones co-expressed along with the target protein's genes into the expression host to produce the lipase in soluble fraction as a bioactive form. The refolding of expressed lipase from IBs (inactive) is another practical strategy which is usually carried out through chemical and physical methods. Based on recent investigations, the current review simultaneously highlights strategies to express the bioactive lipases and recover the bioactive lipases from the IBs in insoluble form.
Yeasts serve as exceptional hosts in the manufacturing of functional protein engineering and possess industrial or medical utilities. Considerable focus has been directed towards yeast owing to its inherent benefits and recent advancements in this particular cellular host. The Pichia pastoris expression system is widely recognized as a prominent and widely accepted instrument in molecular biology for the purpose of generating recombinant proteins. The advantages of utilizing the P. pastoris system for protein production encompass the proper folding process occurring within the endoplasmic reticulum (ER), as well as the subsequent secretion mediated by Kex2 as a signal peptidase, ultimately leading to the release of recombinant proteins into the extracellular environment of the cell. In addition, within the P. pastoris expression system, the ease of purifying recombinant protein arises from its restricted synthesis of endogenous secretory proteins. Despite its achievements, scientists often encounter persistent challenges when attempting to utilize yeast for the production of recombinant proteins. This review is dedicated to discussing the current achievements in the usage of P. pastoris as an expression host. Furthermore, it sheds light on the strategies employed in the expression system and the optimization and development of the fermentative process of this yeast. Finally, the impediments (such as identifying high expression strains, improving secretion efficiency, and decreasing hyperglycosylation) and successful resolution of certain difficulties are put forth and deliberated upon in order to assist and promote the expression of complex proteins in this prevalent recombinant host.
The flexibility and the low production costs offered by plastics have made them crucial to society. Unfortunately, due to their resistance to biological degradation, plastics remain in the environment for an extended period of time, posing a growing risk to life on earth. Synthetic treatments of plastic waste damage the environment and may cause damage to human health. Bacterial and fungal isolates have been reported to degrade plastic polymers in a logistic safe approach with the help of their microbial cell enzymes. Recently, the bacterial strain Ideonella sakaiensis (201-F6) was discovered to break down and assimilate polyethylene terephthalate (PET) plastic via metabolic processes at 30 °C to 37 °C. PETase and MHETase enzymes help the bacterium to accomplish such tremendous action at lower temperatures than previously discovered enzymes. In addition to functioning at low temperatures, the noble bacterium's enzymes have amazing qualities over pH and PET plastic degradation, including a shorter period of degradation. It has been proven that using the enzyme PETase, this bacterium hydrolyzes the ester linkages of PET plastic, resulting in production of terephthalic acid (TPA), nontoxic compound and mono-2-hydroxyethyl (MHET), along with further depolymerization of MHET to release ethylene glycogen (EG) and terephthalic acid (TPA) by the second enzyme MHETase. Enzymatic plastic degradation has been proposed as an environmentally friendly and long-term solution to plastic waste in the environment. As a result, this review focuses on the enzymes involved in hydrolyzing PET plastic polymers, as well as some of the other microorganisms involved in plastic degradation.
Producing recombinant proteins is a major accomplishment of biotechnology in the past century. Heterologous hosts, either eukaryotic or prokaryotic, are used for the production of these proteins. The utilization of microbial host systems continues to dominate as the most efficient and affordable method for biotherapeutics and food industry productions. Hence, it is crucial to analyze the limitations and advantages of microbial hosts to enhance the efficient production of recombinant proteins on a large scale. E. coli is widely used as a host for the production of recombinant proteins. Researchers have identified certain obstacles with this host, and given the growing demand for recombinant protein production, there is an immediate requirement to enhance this host. The following review discusses the elements contributing to the manifestation of recombinant protein. Subsequently, it sheds light on innovative approaches aimed at improving the expression of recombinant protein. Lastly, it delves into the obstacles and optimization methods associated with translation, mentioning both cis-optimization and trans-optimization, producing soluble recombinant protein, and engineering the metal ion transportation. In this context, a comprehensive description of the distinct features will be provided, and this knowledge could potentially enhance the expression of recombinant proteins in E. coli.
This study describes the cloning, expression and functional characterization of α-humulene synthase, responsible for the formation of the key aromatic compound α-humulene in agarwood originating from Aquilaria malaccensis. The partial sesquiterpene synthase gene from the transcriptome data of A. malaccensis was utilized for full-length gene isolation via a 3' RACE PCR. The complete gene, denoted as AmDG2, has an open reading frame (ORF) of 1671 bp and encodes for a polypeptide of 556 amino acids. In silico analysis of the protein highlighted several conserved motifs typically found in terpene synthases such as Asp-rich substrate binding (DDxxD), metal-binding residues (NSE/DTE), and cytoplasmic ER retention (RxR) motifs at their respective sites. The AmDG2 was successfully expressed in the E. coli:pET-28a(+) expression vector whereby an expected band of about 64 kDa in size was detected in the SDS-PAGE gel. In vitro enzyme assay using substrate farnesyl pyrophosphate (FPP) revealed that AmDG2 gave rise to two sesquiterpenes: α-humulene (major) and β-caryophyllene (minor), affirming its identity as α-humulene synthase. On the other hand, protein modeling performed using AlphaFold2 suggested that AmDG2 consists entirely of α-helices with short connecting loops and turns. Meanwhile, molecular docking via AutoDock Vina (Version 1.5.7) predicted that Asp307 and Asp311 act as catalytic residues in the α-humulene synthase. To our knowledge, this is the first comprehensive report on the cloning, expression and functional characterization of α-humulene synthase from agarwood originating from A. malaccensis species. These findings reveal a deeper understanding of the structure and functional properties of the α-humulene synthase and could be utilized for metabolic engineering work in the future.
Owing to the environmental friendliness and vast advantages that enzymes offer in the biotechnology and industry fields, biocatalysts are a prolific investigation field. However, the low catalytic activity, stability, and specific selectivity of the enzyme limit the range of the reaction enzymes involved in. A comprehensive understanding of the protein structure and dynamics in terms of molecular details enables us to tackle these limitations effectively and enhance the catalytic activity by enzyme engineering or modifying the supports and solvents. Along with different strategies including computational, enzyme engineering based on DNA recombination, enzyme immobilization, additives, chemical modification, and physicochemical modification approaches can be promising for the wide spread of industrial enzyme usage. This is attributed to the successful application of biocatalysts in industrial and synthetic processes requires a system that exhibits stability, activity, and reusability in a continuous flow process, thereby reducing the production cost. The main goal of this review is to display relevant approaches for improving enzyme characteristics to overcome their industrial application.
Lipase biocatalysts offer unique properties which are often impaired by low thermal and methanol stability. In this study, the rational design was employed to engineer a disulfide bond in the protein structure of Geobacillus zalihae T1 lipase in order to improve its stability. The selection of targeted disulfide bond sites was based on analysis of protein spatial configuration and change of Gibbs free energy. Two mutation points (S2C and A384C) were generated to rigidify the N-terminal and C-terminal regions of T1 lipase. The results showed the mutant 2DC lipase improved methanol stability from 35 to 40% (v/v) after 30 min of pre-incubation. Enhancement in thermostability for the mutant 2DC lipase at 70 °C and 75 °C showed higher half-life at 70 °C and 75 °C for 30 min and 52 min, respectively. The mutant 2DC lipase maintained the same optimum temperature (70 °C) as T1 lipase, while thermally induced unfolding showed the mutant maintained higher rigidity. The kcat/Km values demonstrated a relatively small difference between the T1 lipase (WT) and 2DC lipase (mutant). The kcat/Km (s-1 mM-1) of the T1 and 2DC showed values of 13,043 ± 224 and 13,047 ± 312, respectively. X-ray diffraction of 2DC lipase crystal structure with a resolution of 2.04 Å revealed that the introduced single disulfide bond did not lower initial structural interactions within the residues. Enhanced methanol and thermal stability are suggested to be strongly related to the newly disulfide bridge formation and the enhanced compactness and rigidity of the mutant structure. KEY POINTS: • Protein engineering via rational design revealed relative improved enzymatic performance. • The presence of disulfide bond impacts on the rigidity and structural function of proteins. • X-ray crystallography reveals structural changes accompanying protein modification.
Enzymes are often required to function in a particular reaction condition by the industrial procedure. In order to identify critical residues affecting the optimum pH of Staphylococcal lipases, chimeric lipases from homologous lipases were generated via a DNA shuffling strategy. Chimeric 1 included mutations of G166S, K212E, T243A, H271Y. Chimeric 2 consisted of substitutions of K212E, T243A, H271Y. Chimeric 3 contained substitutions of K212E, R359L. From the screening results, the pH profiles for chimeric 1 and 2 lipases were shifted from pH 7 to 6. While the pH of chimeric 3 was shifted to 8. It seems the mutation of K212E in chimeric 1 and 2 decreased the pH to 6 by changing the electrostatic potential surface. Furthermore, chimeric 3 showed 10 ˚C improvement in the optimum temperature due to the rigidification of the catalytic loop through the hydrophobic interaction network. Moreover, the substrate specificity of chimeric 1 and 2 was increased towards the longer carbon length chains due to the mutation of T243A adjacent to the lid region through increasing the flexibility of the lid. Current study illustrated that directed evolution successfully modified lipase properties including optimum pH, temperature and substrate specificity through mutations, especially near catalytic and lid regions.
A histidine acid phosphatase (HAP) (PhySc) with 99.50% protein sequence similarity with PHO5 from Saccharomyces cerevisiae was expressed functionally with the molecular mass of ∼110 kDa through co-expression along with the set of molecular chaperones dnaK, dnaJ, GroESL. The purified HAP illustrated the optimum activity of 28.75 ± 0.39 U/mg at pH 5.5 and 40 ˚C. The Km and Kcat values towards calcium phytate were 0.608 ± 0.09 mM and 650.89 ± 3.6 s- 1. The half-lives (T1/2) at 55 and 60 ˚C were 2.75 min and 55 s, respectively. The circular dichroism (CD) demonstrated that PhySc includes 30.5, 28.1, 21.3, and 20.1% of random coils, α-Helix, β-Turns, and β-Sheet, respectively. The Tm recorded by CD for PhySc was 56.5 ± 0.34˚C. The molecular docking illustrated that His59 and Asp322 act as catalytic residues in the PhySc. MD simulation showed that PhySc at 40 ˚C has higher structural stability over those of the temperatures 60 and 80 ˚C that support the thermodynamic in vitro investigations. Secondary structure content results obtained from MD simulation indicated that PhySc consists of 34.03, 33.09, 17.5, 12.31, and 3.05% of coil, helix, turn, sheet, and helix310, respectively, which is almost consistent with the experimental results.