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Ginsenosides, the main pharmacologically active natural compounds in ginseng (Panax ginseng), are mostly the glycosylated products of protopanaxadiol (PPD) and protopanaxatriol (PPT). No uridine diphosphate glycosyltransferase (UGT), which catalyzes PPT to produce PPT-type ginsenosides, has yet been reported. Here, we show that UGTPg1, which has been demonstrated to regio-specifically glycosylate the C20-OH of PPD, also specifically glycosylates the C20-OH of PPT to produce bioactive ginsenoside F1. We report the characterization of four novel UGT genes isolated from P. ginseng, sharing high deduced amino acid identity (>84%) with UGTPg1. We demonstrate that UGTPg100 specifically glycosylates the C6-OH of PPT to produce bioactive ginsenoside Rh1, and UGTPg101 catalyzes PPT to produce F1, followed by the generation of ginsenoside Rg1 from F1. However, UGTPg102 and UGTPg103 were found to have no detectable activity on PPT. Through structural modeling and site-directed mutagenesis, we identified several key amino acids of these UGTs that may play important roles in determining their activities and substrate regio-specificities. Moreover, we constructed yeast recombinants to biosynthesize F1 and Rh1 by introducing the genetically engineered PPT-producing pathway and UGTPg1 or UGTPg100. Our study reveals the possible biosynthetic pathways of PPT-type ginsenosides in Panax plants, and provides a sound manufacturing approach for bioactive PPT-type ginsenosides in yeast via synthetic biology strategies.

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Extended-spectrum b-lactamase (ESBL)-producing Escherichia coli has spread rapidly worldwide and poses a serious threat to human and animal health. This study collected 51 nonreplicate E. coli isolates from 14 different chicken farms in Henan Province in China from December 2007 to August 2008. The prevalence of ESBL-producing E. coli, molecular characterization of the ESBL-related bla genes, including bla TEM , bla SHV and bla CTX-M , and the susceptibilities of these bacteria to various antimicrobial agents were determined. Thirty-one of the 51 isolates were positive for an ESBL phenotype and 29 of these isolates carried one or more bla genes. Twenty-two isolates harboured bla TEM genes and 15 isolates carried bla CTX-M genes (one CTX-M-14, three CTX-M-24 and 11 CTX-M-65). One isolate carried bla ; the remaining bla TEM isolates carried bla TEM-1 with one silent nucleotide base variation (T18C). We believe that this is the first study to report TEM-57 in E. coli isolates. All isolates harbouring bla CTX-M-24 and bla CTX-M-14 and five of the bla CTX-M-65 isolates also harboured the bla TEM-1 gene. To our knowledge, this study is the first to describe detection of CTX-M-65-producing E. coli isolated from chickens. None of the isolates contained the bla SHV gene. Conjugation experiments demonstrated that bla CTX-M and bla TEM genes could be transferred to E. coli DH5a. The results indicate that ESBL frequency has reached an alarming level in chicken isolates in China, with TEM-1 and CTX-M-65 enzymes being the two predominant b-lactamases detected. INTRODUCTIONExtended-spectrum b-lactamases (ESBLs) are rapidly spreading worldwide (Tenover et al., 1999) and presently comprise over 500 variants (http://www.lahey.org/Studies), which are frequently encountered among human and animal clinical Enterobacteriaceae isolates (Bradford, 2001). A typical characteristic of ESBLs is their ability to hydrolyse oxyimino-cephalosporins, which can be inhibited by blactamase inhibitors (Paterson & Bonomo, 2005). ESBLs, particularly TEM, SHV and CTX-M enzymes, exhibit a high degree of diversity (Bonnet, 2004;Livermore et al., 2007). ESBL genes are usually carried by plasmids, facilitating their spread among Gram-negative bacilli. Several surveillance studies have revealed a relatively high prevalence of ESBL-producing organisms in the AsiaPacific area (Hirakata et al., 2005;Wang et al., 2005). In particular, the CTX-M family is believed to be dominant in Asia, as it has appeared or caused outbreaks in many countries (Bonnet, 2004;Munday et al., 2004;Ryoo et al., 2005;Kiratisin et al., 2008;Xiao et al., 2008).Since 1994, ESBL-producing bacteria have become widely disseminated in the People's Republic of China and their molecular characterization has focused mainly on human clinical isolates (Cheng & Chen, 1994;Chanawong et al., 2002;Wang et al., 2005;Xiao et al., 2008;Liu et al., 2009). Several studies worldwide have studied the epidemiology and molecular characterization of ESBL-producing animal clinical isolates (Batchelor et al., ...

The oleaginous yeast Yarrowia lipolytica was metabolically engineered to produce the chamomile sesquiterpene (−)-α-bisabolol in a green and sustainable way.

Cocoa butter (CB) extracted from cocoa beans is the main raw material for chocolate production. However, growing chocolate demands and limited CB production has resulted in a shortage of CB supply. CB is mainly composed of three different kinds of triacylglycerols (TAGs), POP (C16:0–C18:1–C16:0), POS (C16:0–C18:1–C18:0), and SOS (C18:0–C18:1–C18:0). The storage lipids of yeasts, mainly TAGs, also contain relative high-level of C16 and C18 fatty acids and might be used as CB-like lipids (CBL). In this study, we cultivated six different yeasts, including one non-oleaginous yeast strain, Saccharomyces cerevisiae CEN.PK113-7D, and five oleaginous yeast strains, Trichosporon oleaginosus DSM11815, Rhodotorula graminis DSM 27356, Lipomyces starkeyi DSM 70296, Rhodosporidium toruloides DSM 70398, and Yarrowia lipolytica CBS 6124, in nitrogen-limited medium and compared their CBL production ability. Under the same growth conditions, we found that TAGs were the main lipids in all six yeasts and that T. oleaginosus can produce more TAGs than the other five yeasts. Less than 3% of the total TAGs were identified as potential SOS in the six yeasts. However, T. oleaginosus produced 27.8% potential POP and POS at levels of 378 mg TAGs/g dry cell weight, hinting that this yeast may have potential as a CBL production host after further metabolic engineering in future.Electronic supplementary materialThe online version of this article (doi:10.1007/s00253-017-8126-7) contains supplementary material, which is available to authorized users.

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