## 1 Introduction  
Fermented sausage is a representative of traditional fermented meat products, with a unique flavor primarily resulting from the metabolic activities of microorganisms. In traditional natural fermentation, the random colonization of environmental microorganisms led to variability in product quality across batches. Modern fermentation technology ensures controlled flavor and stable quality through targeted inoculation with fermentation strains such as lactic acid bacteria, staphylococci, and yeasts [1]. Among these strains, _Debaryomyces hansenii_ (_D. hansenii_) is a promising yeast strain for enhancing the flavor of fermented meat products. The inoculation of \(D\). _hansenii_ into low-sodium fermented sausages made from boar meat can effectively mask boar taint by generating volatile compounds with fruity and cheesy aromas [2]. In dry-cured pork belly, inoculation with \(D\). _hansenii_ has also been shown to promote muscle protein degradation, enhance amino acid accumulation, and facilitate the formation of aldehydes, esters, alcohols, ketones, and organic acids [3]. These flavor-enhancing effects are generally attributed to the yeast's growth performance, enzymatic activities, and metabolite production [4]. Accordingly, enhancing the fermentation characteristics of \(D\). _hansenii_ is considered a promising strategy for improving the sensory quality of fermented meat products. Modern food biotechnology has improved microbial fermentation performance through strain enhancement approaches such as directed evolution, gene editing, and adaptive evolution targeting tolerance to high osmotic pressure or extreme pH conditions [5]. However, long development cycles and high validation costs often limit these strategies. In contrast, supplementing fermentation substrates with conventional carbon and nitrogen sources offers a practical alternative with lower technical barriers and shorter implementation timelines [6]. Carbon and nitrogen sources not only serve as essential sources of energy and nutrients for microorganisms but also regulate their metabolic pathways. Studies have shown that the microbial utilization of these nutrients is controlled by catabolite carbon repression (CCR) and nitrogen catabolite repression (NCR) mechanisms [7]. The CCR mechanism enables microorganisms to preferentially utilize high-efficiency carbon sources (e.g., glucose) while repressing the expression of genes involved in the metabolism of secondary carbon sources (e.g., lactose and maltose), thereby improving energy utilization efficiency. The NCR mechanism regulates nitrogen utilization by repressing the metabolic pathways of secondary nitrogen sources (e.g., proline and urea) when preferred nitrogen sources (e.g., ammonium ions and glutamine) are abundant, and by activating alternative nitrogen utilization pathways under nitrogen-limited conditions [8]. Furthermore, the properties of carbon and nitrogen sources can directly affect the physicochemical characteristics and sensory properties of fermented meat products. For instance, corn starch, owing to its strong water-binding capacity, can improve moisture retention and enhance the structural integrity of the final product [9]. Soy protein isolate, characterized by its high protein content and low fat composition, is widely used to improve water retention, reduce fat content, and facilitate the development of plant-based meat products [10]. In addition, carbon and nitrogen sources can indirectly influence product quality by modulating microbial metabolic pathways. For example, sucrose can increase oxidative stress in staphylococci, thereby promoting the formation of nitrosyl myoglobin, which enhances the color of dry-cured sausages [11]. Branched-chain amino acids (leucine, isoleucine, and valine) can be metabolized by microorganisms into aldehydes, alcohols, and organic acids, contributing to the malt-like and nutty aromas of fermented meat products [12].