且停酪酒度荒年:釋北魏正始四年禁河南畜牝馬

北魏正始四年禁河南畜牝馬一事,透露出北魏後期文化轉型中不被重視的一面。禁斷畜養牝馬是爲了節約糧食應對災荒,而河南地區之所以畜養大量牝馬,主要是爲了向洛陽的北族上層社會供應酪酒。酪酒是歐亞遊牧世界中廣受歡迎的高級飲品,也可視爲遊牧文化的符號之一。結合漢、唐、元時代的相關記載,本文對北魏洛陽周圍牝馬的數量以及畜養牝馬的穀物消耗進行了推斷,揭示出在農耕尤其是城市地區維持酪酒文化所需的高昂成本,在理解此次禁畜牝馬事件之餘,也對北朝文化轉型問題提出更多層次的思考。

Recent advances in metabolic engineering of microorganisms for production of tyrosol and its derivatives

Tyrosol is a natural phenolic compound with antioxidant,anti-inflammatory and other biological activities,serving as an important precursor of high-value products such as hydroxytyrosol and salidroside.Therefore,the green and efficient biosynthesis of tyrosol and its derivatives has become a research hotspot in recent years.Building cell factories by metabolic engineering of microorganisms is a potential industrial production way,which has low costs and environmental friendliness.This paper introduces the biosynthesis pathway of tyrosol and presents the key regulated nodes in the de novo synthesis of tyrosol in Escherichia coli and Saccharomyces cerevisiae.In addition,this paper reviews the recent advances in metabolic engineering for the production of hydroxytyrosol and salidroside.This review can provide a reference for engineering the strains for the high-yield production of tyrosol and its derivatives.