2-Phenylethanol (2-PE) is an important flavouring ingredient with a persistent rose-like odour, and it has been widely utilized in food, perfume, beverages, and medicine. Due to the potential existence of toxic byproducts in 2-PE resulting from chemical synthesis, the demand for “natural” 2-PE through biotransformation is increasing. L-Phenylalanine (L-Phe) is used as the precursor for the biosynthesis of 2-PE through the Ehrlich pathway by Saccharomyces cerevisiae. The regulation of L-Phe metabolism in S. cerevisiae is complicated and elaborate. We reviewed current progress on the signal transduction pathways of L-Phe sensing, uptake of extracellular L-Phe and 2-PE synthesis from L-Phe through the Ehrlich pathway. Moreover, the anticipated bottlenecks and future research directions for S. cerevisiae biosynthesis of 2-PE are discussed.

Introduction: There are various degrees of defects of cigar filler leaves after air drying.Methods: In order to improve the quality and plant-derived aroma content of cigar filler leaves, nine aroma-producing yeasts were applied in artificially solid-state fermentation of cigar filler leaves in this study. The differences with various yeasts application were compared by chemical composition and GC-MS analysis.Results and discussion: The results showed that 120 volatile components were identified and quantified in cigar filler leaves after fermentation, including aldehydes (25 types), alcohols (24 types), ketones (20 types), esters (11 types), hydrocarbons (12 types), acids (4 types) and other substances (23 types). Based on the analysis of odor activity value (OAV), the OVA of fruity and floral aroma components were higher. It was found that floral aroma are the representative aroma types of cigar filler leaves treated with Clavispora lusitaniae, Cyberlindera fabianii, Saccharomycosis fibuligera and Zygosaccharomyces bailii R6. After being inoculated with Hanseniaspora uvarum J1, Hanseniaspora uvarum J4 and Pichia pastoris P3, the OAV of fruity aroma in cigar filler leaves was the highest, followed by tobacco aroma and woody aroma. The correlation between volatile components of cigar filler leaves with different yeasts was revealed after PCA analysis. It was concluded that the quality of cigar filler leaves was improved, and cigar filler leaves fermented with different yeasts showed different flavor.

Introduction: Cigar wrapper leaves (CWLs) plays a crucial role in reflecting cigar overall quality. Originating from the Qinba region of China, Fangxian Huangjiu (FHJ) is distinctive from other varieties of Huangjiu.Methods: To investigate the effects of FHJ on enhancing the aroma and quality of CWLs, as well as the consequent alterations in microbial communities, Gas Chromatography-Mass Spectrometry (GC-MS) coupled with Odor Active Value (OAV) analysis was utilized to evaluate the volatile aroma components of CWLs.Results and Discussion: The results indicated that the total amount of aroma compounds in CWLs reached 3,086.88 ug/g, increasing of 270.50% and 166.31% compared to the unfermented and naturally fermented groups, respectively. Among them, β-ionone and 4,7,9-megastigmatrien-3-one from the FHJ fermentation group significantly influenced the sensory characteristics of CWLs. Metagenomic results demonstrated that FHJ fermentation enriched the abundance of both shared and unique microbial species in CWLs, while also increased the diversity of differential microbial species. Addition of FHJ effectively altered the microbial community structure of CWLs from a dominance of Staphylococcus to a prevalence of Staphylococcus, Aspergillus, Pseudomonas, and Acinetobacter. The interactions among these diverse microorganisms collectively contribute to the enhancement of the intrinsic quality of CWLs. This paper provides a theoretical basis for improving the quality of CWLs by FHJ and exploring the changes of microbial community structure and interaction between CWLs and FHJ.