Production and characterization of low molecular weight heparosan in Bacillus megaterium using Escherichia coli K5 glycosyltransferases

Quality control, safety assessment and preparation approaches of low molecular weight heparin

Low Molecular Weight Heparins (LMWHs) are well-established for use in the prevention and treatment of thrombotic diseases, and as a substitute for unfractionated heparin (UFH) due to their predictable pharmacokinetics and subcutaneous bioavailability. LMWHs are produced by various depolymerization methods from UFH, resulting in heterogeneous compounds with similar biochemical and pharmacological properties. However, the delicate supply chain of UFH and potential contamination from animal sources require new manufacturing approaches for LMWHs. Various LMWH preparation methods are emerging, such as chemical synthesis, enzymatic or chemical depolymerization and chemoenzymatic synthesis. To establish the sameness of active ingredients in both innovator and generic LMWH products, the Food and Drug Administration has implemented a stringent scientific method of equivalence based on physicochemical properties, heparin source material and depolymerization techniques, disaccharide composition and oligosaccharide mapping, biological and biochemical properties, and in vivo pharmacodynamic profiles. In this review, we discuss currently available LMWHs, potential manufacturing methods, and recent progress for manufacturing quality control of these LMWHs.

Heparosan biosynthesis in recombinant Bacillus megaterium: Influence of N-acetylglucosamine supplementation and kinetic modeling

Heparosan, an unsulfated polysaccharide, plays a pivotal role as a primary precursor in the biosynthesis of heparin-an influential anticoagulant with diverse therapeutic applications. To enhance heparosan production, the utilization of metabolic engineering in nonpathogenic microbial strains is emerging as a secure and promising strategy. In the investigation of heparosan production by recombinant Bacillus megaterium, a kinetic modeling approach was employed to explore the impact of initial substrate concentration and the supplementation of precursor sugars. The adapted logistic model was utilized to thoroughly analyze three vital parameters: the B. megaterium growth dynamics, sucrose utilization, and heparosan formation. It was noted that at an initial sucrose concentration of 30 g L-1 (S1), it caused an inhibitory effect on both cell growth and substrate utilization. Intriguingly, the inclusion of N-acetylglucosamine (S2) resulted in a significant 1.6-fold enhancement in heparosan concentration. In addressing the complexities of the dual substrate system involving S1 and S2, a multi-substrate kinetic models, specifically the double Andrew's model was employed. This approach not only delved into the intricacies of dual substrate kinetics but also effectively described the relationships among the primary state variables. Consequently, these models not only provide a nuanced understanding of the system's behavior but also serve as a roadmap for optimizing the design and management of the heparosan production method.

Advancements in heparosan production through metabolic engineering and improved fermentation

Heparin is one of the most widely used natural drugs, and has been the preferred anticoagulant and antithrombotic agent in the clinical setting for nearly a century. Heparin also shows increasing therapeutic potential for treating inflammation, cancer, and microbial and viral diseases, including COVID-19. With advancements in synthetic biology, heparin production through microbial engineering of heparosan offers a cost-effective and scalable alternative to traditional extraction from animal tissues. Heparosan serves as the starting carbon backbone for the chemoenzymatic synthesis of bioengineered heparin, possessing a chain length that is critically important for the production of heparin-based therapeutics with specific molecular weight (MW) distributions. Recent advancements in metabolic engineering of microbial cell factories have resulted in high-yield heparosan production. This review systematically analyzes the key modules involved in microbial heparosan biosynthesis and the latest metabolic engineering strategies for enhancing production, regulating MW, and optimizing the fermentation scale-up of heparosan. It also discusses future studies, remaining challenges, and prospects in the field.

Sodium sulfate addition increases the bioresource of biologically active sulfated polysaccharides from Antrodia cinnamomea

Fungal sulfated polysaccharides (SPS) have been used in the pharmaceutical industry. In this study, sodium sulfate was employed as an elicitor to induce stress on the mycelia of Antrodia cinnamomea for the biosynthesis of SPS with high sulfate content. Sodium sulfate treatments increased the yield of SPS to 4.46 % and increased the sulfate content to 6.8 mmol/g of SPS. SPS were extracted from A. cinnamomea cultured with 500 mM sodium sulfate; these SPSs are denoted as Na500. Na500 exhibited the highest sulfate content and dose-dependent inhibitory activity against LPS-induced production of macrophage interleukin 6 (IL-6), tumor necrosis factor α (TNF-α), and interleukin 1β (IL-1β). Mechanistically, Na500 hindered the phosphorylation of transforming growth factor-β receptor II (TGFRII), extracellular signal-regulated kinases (ERK), and protein kinase B (AKT) expression. A purified 7.79 kDa galactoglucan, Na500 F3, augmented the anti-inflammation activity by inhibiting LPS-induced TGFβ release. Additionally, Na500 F3 restrained the LPS-induced phosphorylation of p-38, ERK, AKT, and TGFRII in RAW264.7 cells. Na500 F3 impeded the proliferation of lung cancer H1975 cells by inhibiting the phosphorylation of focal adhesion kinase, ERK, and Slug. The anti-inflammation and anticancer properties of Antrodia SPS contribute to its health benefits, suggesting its utility in functional foods.

Production of different molecular weight glycosaminoglycans with microbial cell factories

Glycosaminoglycans (GAGs) are naturally occurring acidic polysaccharides with wide applications in pharmaceuticals, cosmetics, and health foods. The diverse biological activities and physiological functions of GAGs are closely associated with their molecular weights and sulfation patterns. Except for the non-sulfated hyaluronan which can be synthesized naturally by group A Streptococcus, all the other GAGs such as heparin and chondroitin sulfate are mainly acquired from animal tissues. Microbial cell factories provide a more effective platform for the production of structurally homogeneous GAGs. Enhancing the production efficiency of polysaccharides, accurately regulating the GAGs molecular weight, and effectively controlling the sulfation degree of GAGs represent the major challenges of developing GAGs microbial cell factories. Several enzymatic, metabolic engineering, and synthetic biology strategies have been developed to tackle these obstacles and push forward the industrialization of biotechnologically produced GAGs. This review summarizes the recent advances in the construction of GAGs synthesis cell factories, regulation of GAG molecular weight, and modification of GAGs chains. Furthermore, the challenges and prospects for future research in this field are also discussed.

Heparin mimetics as potential intervention for COVID-19 and their bio-manufacturing

The COVID-19 pandemic has caused severe health problems worldwide and unprecedented decimation of the global economy. Moreover, after more than 2 years, many populations are still under pressure of infection. Thus, a broader perspective in developing antiviral strategies is still of great importance. Inspired by the observed multiple benefits of heparin in the treatment of thrombosis, the potential of low molecular weight heparin (LMWH) for the treatment of COVID-19 have been explored. Clinical applications found that LMWH decreased the level of inflammatory cytokines in COVID-19 patients, accordingly reducing lethality. Furthermore, several in vitro studies have demonstrated the important roles of heparan sulfate in SARS-CoV-2 infection and the inhibitory effects of heparin and heparin mimetics in viral infection. These clinical observations and designed studies argue for the potential to develop heparin mimetics as anti-SARS-CoV-2 drug candidates. In this review, we summarize the properties of heparin as an anticoagulant and the pharmaceutical possibilities for the treatment of virus infection, focusing on the perspectives of developing heparin mimetics via chemical synthesis, chemoenzymatic synthesis, and bioengineered production by microbial cell factories. The ultimate goal is to pave the eminent need for exploring novel compounds to treat coronavirus infection-caused diseases.

High-level expression and optimization of pantoate-β-alanine ligase in Bacillus megaterium for the enhanced biocatalytic production of D-pantothenic acid

D-Pantothenic acid (DPA), also known as vitamin B₅ is associated with several biological functions and its deficiency causes metabolic and energetic disorders in humans. Fortification of foods with DPA is the viable option to address this risk. DPA biological production route employs pantoate-β-alanine ligase (PBL) as the key enzyme, which avoids the tedious and time-consuming optical resolution process. The selection of an efficient PBL enzyme is vital for the biological production of DPA. In this study, the panC gene encoding PBL from Escherichia coli, Bacillus megaterium, Corynebacterium glutamicum and Bacillus subtilis was expressed in B. megaterium. B. subtilis derived panC exhibited high PBL activity 61.62 ± 2.15 U/mL. Co-expression of phosphoenolpyruvate carboxykinase (pckA) did not improve the DPA production in B. megaterium. Biocatalytic fed-batch fermentation with externally supplemented precursor substrates (D-pantoic acid and β-alanine) improved DPA titer to 45.56 ± 0.53 g/L. Daily dietary requirements of DPA for different age groups (including babies, small children, athletes and elderly people) is steadily increasing and the improved DPA production addressed in this study offers advantage for its application in fortification of food products meeting the emerging nutritional demand.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13197-021-05093-6.

Engineering precursor and co-factor supply to enhance D-pantothenic acid production in Bacillus megaterium

High-yielding chemical and chemo-enzymatic methods of D-pantothenic acid (DPA) synthesis are limited by using poisonous chemicals and DL-pantolactone racemic mixture formation. Alternatively, the safe microbial fermentative route of DPA production was found promising but suffered from low productivity and precursor supplementation. In this study, Bacillus megaterium was metabolically engineered to produce DPA without precursor supplementation. In order to provide a higher supply of precursor D-pantoic acid, key genes involved in its synthesis are overexpressed, resulting strain was produced 0.53 ± 0.08 g/L DPA was attained in shake flasks. Cofactor CH2-THF was found to be vital for DPA biosynthesis and was regenerated through the serine-glycine degradation pathway. Enhanced supply of another precursor, β-alanine was achieved by codon optimization and dosing of the limiting L-asparate-1-decarboxylase (ADC). Co-expression of Pantoate-β-alanine ligase, ADC, phosphoenolpyruvate carboxylase, aspartate aminotransferase and aspartate ammonia-lyase enhanced DPA concentration to 2.56 ± 0.05 g/L at shake flasks level. Fed-batch fermentation in a bioreactor with and without the supplementation of β-alanine increased DPA concentration to 19.52 ± 0.26 and 4.78 ± 0.53 g/L, respectively. This present study successfully demonstrated a rational approach combining precursor supply engineering with cofactor regeneration for the enhancement of DPA titer in recombinant B. megaterium.

Preparation and characterization of 2-deacetyl-3-O-sulfo-heparosan and its antitumor effects via the fibroblast growth factor receptor pathway

Heparosan, with a linear chain of disaccharide repeating units of → 4) β-D-glucuronic acid (GlcA) (1 → 4)-α-D-N-acetylglucosamine (GlcNAc) (1→, is a potential starting chemical for heparin synthesis. However, the chemoenzymatic synthesis of single-site sulfated heparosan and its antitumor activity have not been studied. In this study, 2-deacetyl-3-O-sulfo-heparosan (DSH) was prepared successively by the N-deacetylation chemical reaction and enzymatic modification of human 3-O-sulfotransferase-1 (3-OST-1). Structural characterization of DSH was shown the success of the sulfation with the sulfation degree of 0.87. High performance gel permeation chromatography (HPGPC) analysis revealed that DSH had only one symmetrical sharp peak with a molecular weight of 9.6334 × 10⁴ Da. Biological function studies showed that DSH could inhibit tumor cell (A549, HepG2 and HCT116) viability and induce the apoptosis of A549 cells. Further in vitro mechanistic studies showed that DSH may induce apoptosis via the JNK signaling pathway, and the upstream signal of this process may be fibroblast growth factor receptors. These results indicated that DSH could be developed as one of a potential chemical for tumor treatment.

Combinatorial approach for improved production of whole-cell 3-aminopropionic acid in recombinant Bacillus megaterium: codon optimization, gene duplication and process optimization

In this study, we aimed to develop a Bacillus megaterium based whole-cell biocatalyst for the bio-production of 3-aminopropionic acid (3-APA). l-aspartate-α-decarboxylases (ADC) (EC: 4.1.1.11) from Escherichia coli, B. megaterium, Corynebacterium glutamicum, and Bacillus subtilis were expressed in B. megaterium. B. subtilis derived ADC (panD _Bs ) exhibited the highest ADC activity of 0.9 ± 0.02 U/mL in recombinant B. megaterium. Combination of codon optimization and gene duplication strategies resulted in 415.56% enhancement of ADC activity compared to panD _Bs . The culture growth conditions of B. megaterium (BMD-7) for 3-APA production were optimized as follows: inducer concentration, 0.5% (w/v); time of induction, 3 h; induction temperature, 37 °C and post-induction incubation time, 8 h. Improvement of the whole-cell biocatalytic process efficiency, was dealt by optimization of reaction temperature, reaction pH, metal ion additives and l-aspartic acid concentration. Shake flask level experiments yielded an enhanced 3-APA titer (16.18 ± 0.26 g/L) and a yield of 0.89 g/g under optimized conditions viz., 45 °C, pH 6.0 and 20 g/L of l-aspartic acid. This study demonstrates the potential of B. megaterium for 3-APA production and paves the scope for the development of 3-APA producing strains in near future.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02885-7.

Recombinant production of poly-(3-hydroxybutyrate) by Bacillus megaterium utilizing millet bran and rapeseed meal hydrolysates

Fermentative poly-3-hydroxybutyrate (PHB) production is mainly limited by the cost of raw material. In this present study, low-cost feedstock viz., millet bran residue (MBRH) and rapeseed meal hydrolysates were successfully utilized for PHB production. Metabolic engineering of Bacillus megaterium by co-expression of both precursor (phbRBC) and NADPH cofactor regeneration (zwf) genes resulted in 2.67-fold enhancement in PHB accumulation compared to wild strain. Modified logistic model characterized B.megaterium growth and PHB production effectively. The kinetic analysis proved that maximum cell concentration (15.01 g.L^-1) and growth-associated constant (0.22 g.g^-1) were found to be higher for initial MBRH concentration (S₀ = 20 g.L^-1). PHB production kinetics elucidated its expression in B.megaterium was growth-associated. PHB synthesized by B.megaterium was characterized using FTIR, NMR, XRD, DSC/TGA, FESEM and the physio-chemical properties enumerated its as a potential biodegradable plastic for industrial application.

Application of Dual Promoter Expression System for the Enhanced Heparosan Production in Bacillus megaterium

Heparosan, a capsular polysaccharide synthesized by certain pathogenic bacteria, is a promising precursor for heparin production. Heparosan production is catalyzed by the formation of KfiC-KfiA complex and the subsequent action of KfiC and KfiA proteins. Polycistronic expression of kfiC and kfiA in Bacillus megaterium yielded an unbalanced expression of KfiC and KfiA proteins resulted in decreased heparosan production. In this study, dual promoter plasmid system was constructed to increase the expression levels of KfiC and KfiA proteins. Dual promoter plasmid system along with UDP-glucuronic acid pathway overexpression (CADuet-DB) increased the heparosan production to 203 mg/L in shake flask experiments. Batch fermentation of strain CADuet-DB under controlled conditions yielded a maximum heparosan concentration of 627 mg/L, which is 59% higher than strain CA-DB. A modified logistic model is applied to describe the kinetics of heparosan production and biomass growth. Fed batch fermentation resulted in 3-fold enhancement in heparosan concentration (1.96 g/L), compared to batch fermentation. Nuclear magnetic resonance analysis revealed that heparosan from strain CADuet-DB was similar to Escherichia coli K5 heparosan. These results suggested that dual promoter expression system is a promising alternative to polycistronic expression system to produce heparosan in B. megaterium.

Advances in the preparation and synthesis of heparin and related products

Heparin is a naturally occurring glycosaminoglycan from livestock, principally porcine intestine, and is clinically used as an anticoagulant drug. A limitation to heparin production is that it depends on a single animal species and potential problems have been associated with animal-derived heparin. The contamination crisis in 2008 led to a search for new animal sources and the investigation of non-animal sources of heparin. Over the past 5 years, new animal sources, chemical, and chemoenzymatic methods have been introduced to prepare heparin-based drugs. In this review, we describe advances in the preparation and synthesis of heparin and related products.