Abstract
Backgroundp-Hydroxycinnamic acid (pHCA) is an aromatic compound that serves as a starting material for the production of many commercially valuable chemicals, such as fragrances and pharmaceuticals, and is also used in the synthesis of thermostable polymers. However, chemical synthesis of pHCA is both costly and harmful to the environment. Although pHCA production using microbes has been widely studied, there remains a need for more cost-effective methods, such as the use of biomass as a carbon source. In this study, we produced pHCA using tyrosine ammonia lyase-expressing Streptomyces lividans. In order to improve pHCA productivity from cellulose, we constructed a tyrosine ammonia lyase- and endoglucanase (EG)-expressing S. lividans transformant and used it to produce pHCA from cellulose.ResultsA Streptomyces lividans transformant was constructed to express tyrosine ammonia lyase derived from Rhodobacter sphaeroides (RsTAL). The transformant produced 786 or 736 mg/L of pHCA after 7 days of cultivation in medium containing 1% glucose or cellobiose as the carbon source, respectively. To enhance pHCA production from phosphoric acid swollen cellulose (PASC), we introduced the gene encoding EG into RsTAL-expressing S. lividans. After 7 days of cultivation, this transformant produced 753, 743, or 500 mg/L of pHCA from 1% glucose, cellobiose, or PASC, respectively.ConclusionsRsTAL-expressing S. lividans can produce pHCA from glucose and cellobiose. Similarly, RsTAL- and EG-expressing S. lividans can produce pHCA from glucose and cellobiose with excess EG activity remaining in the supernatant. This transformant demonstrated improved pHCA production from cellulose. Further enhancements in the cellulose degradation capability of the transformant will be necessary in order to achieve further improvements in pHCA production from cellulose.
Highlights
In a world in which fossil fuels are becoming scarcer and more expensive, the production of chemicals from renewable feedstocks represents a promising means of meeting energy demands [1,2,3,4]
A UV analysis of the putative p-hydroxycinnamic acid (pHCA) highperformance liquid chromatography (HPLC) fraction isolated from the culture supernatant of S. lividans/ pURsTAL revealed the presence of three prominent absorption peaks in the 200–350 nm region that were consistent with the peaks produced upon analysis of standard pHCA (Figure 1B)
We carried out pHCA production using S. lividans/pURsTAL using the modified TSB medium with 1% glucose and the additional L-tyrosine, which is the precursor of pHCA
Summary
In a world in which fossil fuels are becoming scarcer and more expensive, the production of chemicals from renewable feedstocks represents a promising means of meeting energy demands [1,2,3,4]. The aromatic compound p-hydroxycinnamic acid (pHCA) serves as the starting compound for the production of numerous commercially valuable chemicals, including flavors, fragrances, pharmaceuticals, biocosmetics, and health and nutrition products [9], and is used in the synthesis of thermostable polymers [10]. Chemical synthesis of pHCA is not costeffective and results in the production of large amounts of harmful byproducts [11]. Tyrosine ammonia lyase (TAL), a member of the aromatic amino acid lyase family, catalyzes the nonoxidative deamination of L-tyrosine to trans-pHCA [12]. Tyrosine ammonia lyase derived from the oleaginous yeast Rhodotorula glutinis has been used to produce pHCA by introducing R. glutinis TAL into P. putida, E. coli, and S. cerevisiae [9,11]. Because RsTAL demonstrates high substrate specificity for tyrosine, selective production of pHCA is possible
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