The aminoshikimic acid pathway in bacteria as source of precursors for the synthesis of antibacterial and antiviral compounds

Abstract The aminoshikimic acid (ASA) pathway comprises a series of reactions resulting in the synthesis of 3-amino-5-hydroxybenzoic acid (AHBA), present in bacteria such as Amycolatopsis mediterranei and Streptomyces. AHBA is the precursor for synthesizing the mC7N units, the characteristic structural component of ansamycins and mitomycins antibiotics, compounds with important antimicrobial and anticancer activities. Furthermore, aminoshikimic acid, another relevant intermediate of the ASA pathway, is an attractive candidate for a precursor for oseltamivir phosphate synthesis, the most potent anti-influenza neuraminidase inhibitor treatment of both seasonal and pandemic influenza. This review discusses the relevance of the key intermediate AHBA as a scaffold molecule to synthesize diverse ansamycins and mitomycins. We describe the structure and control of the expression of the model biosynthetic cluster rif in A. mediterranei to synthesize ansamycins and review several current pharmaceutical applications of these molecules. Additionally, we discuss some relevant strategies developed for overproducing these chemicals, focusing on the relevance of the ASA pathway intermediates kanosamine, AHAB, and ASA.


Elucidation of the Aminoshikimic Acid Pathway
Feeding experiments of the SA pathway intermediates SA, QA, and DHQ to synthesize mC 7 N units of ansamycins and mitomycins repeatedly failed in experiments with A. mediterranei. Additionally, labeled [2-13 C]-SA was not incorporated into the C 7 N units to synthesize ansatrienin but efficiently labeled the cyclohexane carboxylic acid moiety, leading to conclude that the biosynthesis of the C 7 N units must branch off from the SA pathway before SA.
Further genetic experiments showed that the branching point for the synthesis of C 7 N in the biosynthesis of rifamycin was before DHQ (Haber et al., 2002;Hornemann et al., 1974Hornemann et al., , 1980Karlsson et al., 1974;White & Martinelli, 1974).
The iminoE4P and PEP are condensed to aminoDAHP by RifH. This step is followed by three parallel reactions to the SA pathway to yield aminoDHQ, aminoDHS, and AHBA catalyzed by RifG, RifJ, and RifK, respectively. Remarkably, AHBA synthase (RifK) possess two catalytic functions: As a homodimer, it catalyzes the last reaction in the pathway to produce AHBA from aminoDHS, and in the iminoE4P stage, in a complex with the oxidoreductase RifL, catalyzes the transamination of UDP-3-keto-D-glucose to 3-amino-3-deoxy-UDP-glucose ( Fig. 2A) (Floss et al., 2011;Kang et al., 2012). Finally, ASA is synthesized by reducing aminoDHS by the activity of the aminoshikimate dehydrogenase encoded by the rifI gene in A. mediterranei ( Fig. 1) (Guo & Frost, 2004).
All ansamycin antibiotics are composed of a benzoic or naphthalenic chromophore bridged by an aliphatic polyketide chain that terminates at the chromophore with an amide linkage (Watanabe et al., 2003). The aromatic moiety is derived from an AHBA starter unit activated by a nonribosomal peptide synthetase-like mechanism. The chain extension by subsequent additions of methylmalonyl and malonyl extender units is performed by the activity of modular polyketide synthases (PKSs) (Floss et al., 2011;Kang et al., 2012;Watanabe et al., 2003). A comprehensive review of the biosynthesis of naphtalenic ansamycins-including the rifamycins, streptovaricins, rubradirins, naphthomycins, hygrocins, ansalactam A, chaxamycins, and divergolides is reported by Kang et al. (2012). Mitomycins and the compound FR-900482 are compounds with similar structures produced by diverse Streptomyces species and represent a family of antitumor agents of extraordinary potency (Kang et al., 2012). Based on the nature and stereochemistry of the radical at C-9, mitomycins are classified in mitomycin A, C, and F, whereas there are only two members of type FR, FR-900482, and FR-66979. The aromatic rings of the mitomycins are quinones, whereas in FR-900482 are phenols (Judd & Williams, 2004;Kang et al., 2012). FR-900482 was isolated from cultures of S. sandansis no. 6897 and possess an azidine and a carbamoylated hydroxymethyl moiety resembling the mitomycins' structure and suggests a common biosynthetic pathway (Kang et al., 2012). FR-900482 possesses an attractive antitumor activity, superior to mitomycin C Shimomura et al., 1987). The structure of FR-900482-showing a unique hydroxylamine hemiacetal-challenged its synthetic synthesis, resulting in its total chemical synthesis and the synthesis of several enantioselective synthesis analogs (Kambe et al., 2001). Fig. 3 shows representative chemical structures of ansamycins and mitomycins derived from AHBA.

The Biosynthetic Clusters for Rifamycin and Mitomycin Biosynthesis Are Examples of the Genetic Organization of the Biosynthetic Pathways of Ansamycins and Mitomycins
The ∼90-kb rifamycin biosynthetic gene cluster (rif cluster) from several A. mediterranei and several Streptomyces species strains includes 43 genes organized in 10 operons and starts with rifS and ends with rifZ (Fig. 4A). The cluster includes an operon comprising five types of modular polyketide synthases (rifABCDE), associated with the genes involved in the synthesis of AHBA (rifGHIKLMN) and rifJ (in a separated operon). Additionally, it comprises genes controlling the post-polyketide backbone modifications and conversion of rifamycin and its export (Floss et al., 2011;Liu et al., 2020c). Furthermore, two regulator genes are Diversity of derived natural products from 3-amino-5-hydroxybenzoic acid (AHBA). Chemical structure of AHBA shown as reference. Chemical structures of ansamycin derivatives. Chemical structure of mitomycin derivatives. The AHBA moiety is highlighted in bold bonds and atoms in the chemical structures shown. For rifamycin: R = CH 2 COOH for rifamycin B, R = H for rifamycin SV. For saliniketal: R = H for saliniketal A, R = OH for saliniketal B. For mitomycin: R 1 = OCH 3 and R 2 = H for mitomycin A, R 1 = NH 2 and R 2 = H for mitomycin C, R 1 = OCH 3 and R 2 = CH 3 for mitomycin F. Modified from Kang et al. (2012). located in the rif cluster, RifZ (rifZ), a LuxR family transcriptional regulator activating the transcription of all the genes of the cluster; and RifQ (rifQ), proposed as involved in the control of the reduction of the intracellular toxicity of rifamycin by regulating the expression of the rifamycin exporter RifP (rifP) (Fig. 4A) Liu et al., 2020c). Remarkably, besides RifZ, GlnR, a global transcriptional regulator in actinomycetes involved in the modulation of assimilation and utilization of diverse carbon sources; nitrogen sources (ammonium, urea, or nitrate), as in antibiotic biosynthesis, is also involved in the activation of the positive regulator of RifZ, promoting the indirect positive regulation of the entire rif cluster. Additionally, GlnR was proposed to promote the  , rifM; N, rifN; O, rifO; 2, orf2; P, rifP; Q, rifQ; 3, orf3; 4, orf4; 5, orf5; 6, orf6; 7, orf7; 8, orf8; 9, orf9; 10, orf10; 11, orf11; 17, orf17; 18, orf18; 19, orf19; 20, orf20; R, rifR; 13, orf13; 14, orf14 biosynthesis of AHBA directly by activating the transcription of rifK coding for AHBA synthase (Liu et al., 2020c) (Fig. 4B).
As ansamycins, mitomycins are synthesized from AHBA by the encoded genes in the ∼55-kb mitomycin biosynthetic cluster, comprising 47 genes for the biosynthesis of mitomycin C (MCC) in Streptomyces lavendulae, including homologous to the genes involved in the synthesis of iminoE4P and AHBA in A. mediterranei and Streptomyces coelicolor in the rif cluster, and the genes involved in the synthesis of mitomycin from AHBA and N-acetylglucosamine (GlcNAc) (Bass et al., 2013;Nguyen & Yokoyama, 2019). Furthermore, the coupling mechanism of the building blocks (AHBA and GlcNAc) for mitomycin biosynthesis was recently elucidated. In the proposal mechanism, AHBA is first loaded onto an MmcB acyl carrier protein (ACP) by the activity of MitE (acyl ACP synthetase) followed by a transfer of GlcNAc from UDP-GlcNAc by MitB, suggesting that metabolic intermediates in the early stages in the biosynthesis of mitomycins are coupled to MmcB (Nguyen & Yokoyama, 2019).

Relevant Biological Activities of Compounds Derived from AHBA
Ansamycins produced by A. mediterranei include the rifamycins, from which derive a large number of chemically synthesized compounds, including rifampicin, rifabutin, rifapentine, and rifaximin (Kang et al., 2012;Liu et al., 2020c). These compounds are still used as first-line antimycobacterial drugs against Mycobacterium tuberculosis and Mycobacterium leprae by inhibiting their RNA polymerase activity (Liu et al., 2020c).
Saliniketal A and B are interesting bicyclic polyketide compounds because of their structural relationship to the ansa side chain (C-1 through C-15) of the rifamycin antibiotics (Fig. 3). These compounds were isolated from supernatant cultures of several strains of the marine actinomycetes Salinispora arenicola. These compounds possess anticancer activity associated with the possible inhibition of the induction of ornithine decarboxylase (ODC). Inhibition of ODC activity is proposed to decrease polyamines' cellular concentration, considered as an effective strategy to prevent carcinogenesis (Kang et al., 2012;Williams et al., 2007).
Mitomycin C is the most important member of mitomycins, with a relevant anticancer activity. Mitomycin C is used to treat different cancers such as head and neck sarcoma, lung carcinoma, bladder cancer, hepatic carcinoma, esophageal carcinoma, pancreatic, and colorectal or anal cancer (Baindara & Mandal, 2020;Bass et al., 2013;Wolters et al., 2021;Zhang et al., 2020). Mitomycin C is a potent DNA cross-linking alkylating agent by two postulated alkylating centers. The alkylation of DNA targets multiple guanine residues by reductive activation resulting in six covalent DNA adducts. DNA alkylation will block DNA synthesis, inhibiting cell proliferation, and several of the formed adducts are reported to induce cancer cell death (Wolters et al., 2021;Zhang et al., 2020). Mitomycin C possesses other relevant biological activities such as an antibiotic, antifibrotic, and immunosuppressive agent. However, severe adverse effects resulting from its high toxicity have limited its clinical application significantly .

ASA as the Precursor for Oseltamivir Phosphate Synthesis
Oseltamivir phosphate (Tamiflu) is one of the most potent oral anti-influenza neuraminidase inhibitors used to treat both seasonal and pandemic influenza (Sagandira et al., 2020;Tompa et al., 2021). Shikimic acid was initially used as the substrate for the chemical synthesis of Tamiflu by Gilead Sciences in 1995, codevel-oped and marketed with F. Hoffmann-La Roche Ltd., and released commercially in 1999 (Sagandira et al., 2020). Although there are more than 70 OSP synthesis processes nowadays, Roche's industrial synthesis process from shikimate is the route that currently provides all OSP worldwide (Magano, 2009;Sagandira et al., 2020). Roche's industrial synthesis for OSP from SA utilizes the azide chemistry to incorporate a 1,2,-diamine moiety, but this process possesses critical steps, including the safety handle of the thermally unstable azide reagents and intermediates at a large scale (Sagandira et al., 2020) As Roche's chemosynthetic route for OSP synthesis from SA involves the azide chemistry, the presence of an amino group at C5 in the ASA's molecule represents an advantage over SA as the substrate for the chemical synthesis of OSP, avoiding the requirement of azide chemistry to incorporate the 1,2,-diamine moiety in the aromatic ring, improving the synthesis of OSP and other oseltamivir carboxylates significantly (Diaz Quiroz et al., 2014;Frost & Guo, 2011;Magano, 2009).
Its extraction has ensured the SA supply of the synthesis of OSP from extensive plantations of Chinese star anise (mainly Illicium religiosum) and its production through fermentative processes using mainly engineered overproducing strains of Escherichia coli (Chandran et al., 2003;Diaz Quiroz et al., 2014;Martínez et al., 2015;Rodriguez et al., 2013;Sagandira et al., 2020). However, significant efforts are needed to produce ASA by biotechnological processes as a possible substrate for the chemical synthesis of OSF.

Metabolic Engineering Strategies for the Microbial Production of ASA Pathway Intermediates Kanosamine, ASA, and AHBA
Given the relevance of kanosamine, ASA, and AHBA, intuitive metabolic engineering strategies to obtain native or heterologous overproducing bacterial strains have been proposed to overproduce these metabolites. Strategies for overproducing kanosamine should consider an increased availability of kanosamine or kanosamine-6-P by channeling glucose flux to their synthesis without affecting the glucose flux to the central carbon metabolism pathways (glycolysis and the PPP). As kanosamine shows antibiotic activity (Janiak & Milewski, 2018), it is necessary to avoid its intracellular accumulation through an efficient conversion to iminoE4 (Frost & Guo, 2011). Remarkably, the metabolic engineering strategies for the overproduction of ASA and AHBA also should avoid the competence of the SA pathway reaction for PEP (PEP + E4P → DAHP), and favoring its flow toward the synthesis of aminoDAHP through the ASA pathway (PEP + imoniE4P → aminoDAHP); otherwise, producing strains, particularly for overproduction of ASA purposes, should avoid SA contamination as resulted previously (Guo & Frost, 2004).

Strategies for the Overproduction of Kanosamine
The kanosamine (3-amino-3-deoxy-D-glucopyranose) was first isolated as a byproduct of the acid hydrolysis of kanamycin but was further isolated from cultures of former Bacillus aminoglycosides (now Bacillus pumillus) (Umezawa, 1968;Umezawa et al., 1967). In A. mediterranei, the kanosamine is synthesized from UDPglucose by six enzymatic reactions (Fig. 2A). The synthesis of kanosamine from glucose-6-P by three enzymatic reactions, was present and characterized in Bacillus subtilis UW85 and is encoded by the genes kabABC, encoding for similar enzymes encoded by the ntdABC operon in B. subtilis (Prasertanan & Palmer, 2019;  Luo et al., 2021;Zhang et al., 2017) Ansalactam A Possess a γ -lactam residue with an aliphatic side chain, in which AHBA-derived amino group is spiro attached to the naphthalenic backbone. The C22-C27 aliphatic side chain of the lactam represents a novel polyketide biosynthetic building block.
Antibiotics currently used to the treatment of tuberculosis and leprosy, anticancer drug inhibiting heat-shock protein 90.
Displayed activity against Bacillus subtilis and Mycobacterium vaccae.
Ansamitocin AP-3 is the most potent antitumor agent used as payload in many antibody conjugates, such as trastuzumab emtansine, FDA approved for breast cancer treatment. AP-3 can strongly depolymerize microtubule assembles in the mitotic cell phase cycle.
Actinosynnema pretiosum ATCC31565 (Du et al., 2017;Li et al., 2018; Ansatrienin Small molecules contain a 21-membered macrocyclic lactam ring and a cyclohexanoyl moiety attached via alanyl side chain attached to the C-11 hydroxyl group of the ansa ring.
Exhibit potent activity against fungi, yeasts, and cytotoxicity. Limited antibacterial activity.
Streptomyces collinus, Streptomyces sp. XZQH13 (Shi et al., 2016;Wang et al., 2018) Vetter et al., 2013) (Fig. 2B). B. pumillus ATCC 21143 was reported as a higher natural producer of kanosamine from D-glucose, resulting in titers up to 20 g/l in 28% mol/mol yield from glucose (Table 2) (Guo & Frost, 2004). The heterologous expression of the kanosamine biosynthetic pathway from A. mediterranei, B. subtilis, and B. pumillus in E. coli was explored to determine if the heterologous system could be manipulated to maximize kanosamine production. Recombinant E. coli PSNI.39 carrying the plasmid pSN1.292/ntdCAB with the ntdABC genes from B. subtilis 168 produced 12.7 g/l kanosamine in 6% mol/mol yield from glucose, showing a further increment to 18 g/l by blocking the glycolytic pathway by a mutation in the E. coli housekeeping pgi-encoded phosphoglucose isomerase. Remarkably, the production of kanosamine resulted in the accumulation of L-glutamic acid in supernatant cultures of the pgimutant. This result suggested that increased L-glutamate accumulation could have a beneficial effect on the heterologous production of kanosamine in E. coli expressing the Bacillus ntd biosynthetic genes, as L-glutamate is the cosubstrate for NtdA (pyridoxal phosphate-dependent 3-oxo-glucose-6-phosphate: glutamate aminotransferase) (Fig. 2B) (Miller, 2018).

Strategies for the Overproduction of AHBA for the Biosynthesis of Ansamycins
The biosynthesis of the naphtalenic ansamycins is a complex biosynthetic process starting with the synthesis of the precursor AHBA in the ASA pathway, and it is further loaded onto a type I PKS, where several rounds of elongation occur, and the final polyketide cycling and modification of the chain yield a macrocyclic lactam (Kang et al., 2012;Wang et al., 2017). The importance of the intracellular availability of AHBA in the production of ansamycin polyketides such as rifamycin and geldanamycin was demonstrated in engineered derivatives of Streptomyces hygroscopicus XM201. The transcriptomic analysis of the producing mutant led to identifying that PKS genes gdmA1-A3 were downregulated compared to that involved in AHBA biosynthesis and postmodifications. Upregulation of PKS genes under a strong promoter (5063p) increased its expression significantly and resulted in a 39% increment in geldanamycin yield. Nevertheless, exogenous feed of AHBA showed that this precursor was now the rate-limiting step in the biosynthetic process. Overexpression of the AHBA biosynthetic cluster (orf990-orf995) assembled under the strong promoter 5063p increased geldanamycin yield both in the wildtype and derivative strains. The combined expression of PKS and AHBA biosynthetic cassettes increased the yield of geldanamycin by 88% in the producing strains compared to the wild-type strain, highlighting the relevance in the availability of AHBA in the engineered strains . The elucidation of the transcriptional control mechanisms of the rif cluster for the synthesis of rifamycin in A. mediterranei by GlnR, the global nitrogen regulator in this bacterium, showed that GlnR binds specifically to the upstream region of rifZ, encoding for the RifZ specific activator of the rif cluster, acting as an indirect regulator of the entire biosynthetic cluster. Furthermore, GlnR was also determined to bind to the upstream region of rifK, coding for the AHBA synthase, acting as a direct activator of the supply of AHBA for the synthesis of rifamycin (Liu et al., 2020c) (Fig. 4B).
The heterologous expression of AHBA biosynthetic genes in E. coli resulted in the successful production of this precursor unit for the potential synthesis of diverse ansamycins and remarkably as a source of amine-substituted SA derivatives. A heterologous hybrid AHBA biosynthetic pathway expressed in E. coli BAP1 includes rifF, rifH, rifK, rifL, rifM, and rifN genes; the bicistronic RifA construct and the pccB and accA1 genes from S. coelicolor. Cultures of this derivative strain produced 2,6-dimethyl-3,5,7-trihydroxy-7-(3´-amino-5´-hydroxyphenyl)-2,4-heptadienoic acid (P8/1-09), an intermediate of the rifamycin biosynthetic pathway, AHBA; and the amine-derivatives aminoDAHP and aminoDHS. These results provided a relevant basis for further heterologous production and manipulation of AHBA-derived polyketides and intermediates of the aminoSA pathway in E. coli (Watanabe et al., 2003). Guo and Frost (2004) reported the first microbial production of ASA from glucose as the carbon source in cultures of A. mediterranei ATCC 21789 as in E. coli SP1.1. Cloning of the rifI gene from A. mediterranei in the plasmid PJG8.219A/pamy rifI amy ermE kan neo (Table 2) and transformation into this bacterium resulted in the production of 0.2 g/l of ASA in 0.4 mol/mol yield from glucose and 1.4 g/l of rifamycin B under controlled culture conditions. Further derivatives of E. coli SP1.1 aroKL -(previously used as the genetic host for the production of SA [Chandran et al., 2003]) were transformed with plasmid pJG5.166A/rifI aroE tktA ( Table 2) and cultures of this derivative strain under controlled fermentation conditions with the external addition of kanosamine resulted in the production of 0.81 g/l ASA and 3.7 g/l SA. Finally, these authors explored a coculture with B. pumillus ATCC 21143 and E. coli SP1.1 aroKL -/pJG6.181B rifI aroE tktA glk (Table 2). In this system, B. pumillus produced kanosamine from glucose-6-P to the culture medium and internalized by E. coli SP1.1 to produce ASA by the sequential intracellular phosphorylation of kanosamine isomerization kanosamine 6-phosphate and fragmentation of aminoF6P to form iminoE4P. Further condensation of PEP with iminoE4P by the native DAHP synthase isoenzymes of E. coli (aroF, aroG, aroH) results in aminoDAHP, which was sequentially converted to ASA by the enzymes of the SA pathway of E. coli AroB (3-dehydroquinate synthase, aroB), AroD (DHAQ dehydratase, aroD), and AroE (shikimate dehydrogenase, aroE) resulting in the production of 1.1 g/l of ASA and 3.4 g/l of SA (Guo & Frost, 2004). Given the relevance of ASA as a possible starting material in the synthesis of OSF antiviral for the treatment of seasonal and pandemic influenza, the optimization of the synthesis process in E. coli or some other host (e.g., Corynebacterium glutamicum [Kogure et al., 2016]) is of great relevance.

The Impact of the Heterologous Expression of Non-ASA Pathway Genes in the Synthesis of Rifamycins
When the liquid cultures of A. mediterranei produce rifamycins reach the stationary phase, it exhibits a high viscosity associated with filamentous bacteria growth. This behavior results in the accumulation of unwanted rifamycins such as rifamycin W in supernatant cultures. The heterologous expression of the hemoglobin encoding gene vhb from Vitreoscilla stercoraria under the control of the PermE promoter in the A. lactamdurans plasmid pULVK2 in A. mediterranei resulted in the enrichment in the production of rifamycin B instead of the unwanted rifamycin W under low aeration conditions by increasing the oxygen-dependent production of rifamycin B. Addition of barbital to cultures of A. mediterranei promotes the production of rifamycin B exclusively. The expression of the hemoglobin vhb gene under low aeration cultures of A. mediterranei resulted in a 13.9% higher production of rifamycin B in cultures with barbital compared to the parental strain and increased to 29.5% without barbital (Priscila et al., 2008).
Further inclusion of the vhb gene bounded to cytochrome P450 (rif-orf5) gene from rifamycin biosynthetic cluster of A. mediterranei increased 1.5-fold higher rifamycin B production than the transformant with only the vhb gene and 2.2-fold higher than the parental strain. The expression of fused genes vhb-orf5 facilitated oxygen availability for the limiting steps for the synthesis of rifamycin B (Mejía et al., 2018).

Conclusion
As many metabolic aromatic intermediates and final compounds produced by biosynthetic processes show broad biological activity of pharmaceutical relevance such as antibiotics, anticancer agents, and enzyme inhibitors, it is relevant to understand the biosynthetic and control mechanisms involved in its production, particularly in microbial strains with prospects for industrial production. The ASA pathway has been extensively studied because AHBA is the key precursor for synthesizing a great diversity of secondary metabolites such as ansamycins and mitomycins. The relevance of the availability of AHBA as a key structural unit for the synthesis of ansamycins and mitomycins has been demonstrated by applying different omics such as genomics, transcriptomics, metabolomics, and fluxomics (Kogure et al., 2016;Liu et al., 2020b;Wang et al., 2017;Zhang et al., 2017). Several metabolic engineering strategies have been developed to increase the availability of AHBA in several species of Streptomyces and A. mediterranei, resulting in the efficient optimization in the production of target compounds such as ansamycins, geldanamycin, and rifamycins. Remarkably, the successful heterologous expression of AHBA biosynthetic genes in E. coli has provided the basis for further genetic and metabolic manipulations of AHBA-derived polyketides. Additionally, the construction of genome-scale models resulting from omic studies, its validation by predicting microbial growth under controlled conditions, and evaluating the role of critical genes in the synthesis of compounds such as ansamitocins (T. Liu et al., 2020b) could provide a valuable basis for the rational modification of the biosynthetic metabolism of AHBA and further elongation and modification steps in the biosynthesis of ansamycins and mitomycins antibiotics.
Another highly relevant intermediate of the ASA pathway is aminoshikimate. The relevance of this compound, particularly as a chemical precursor for the synthesis of OSP, the potent neuraminidase inhibitor of seasonal and pandemic influenza viruses, over SA, and its use in the synthesis of other oseltamivir carboxylates. Its production is particularly relevant because influenza viruses are the third most studied viruses after SARS and HIV ones, for the relevant implications in public health (Tompa et al., 2021). The application of metabolic engineering strategies for its production should consider the efficient production of the key precursor kanosamine and its efficient conversion to aminoDAHP instead of DAHP to avoid SA contamination. Possible strategies of cocultures with kanosamine producing Bacillus strains and selecting proper engineered E. coli hosts to produce ASA (avoiding the production of SA) could improve the valuable aromatic compound as the substrate for the chemical synthesis of OSP.