## 4 Conclusions  
This study initially assessed the effects of simple and complex carbon and nitrogen sources on the fermentation characteristics of local _D. hansenii_. The results demonstrated that the complex carbon and nitrogen sources, including corn starch and soy protein isolates, were particularly effective. Both sources exhibited good water retention properties. Corn starch, serving as a slow-release carbon source, maintained a stable energy supply, boosting colony counts, protease activity, and product brightness. Soy protein isolates, providing a stable nitrogen source and alleviating the NCR effect, led to enhanced growth and protease secretion in _D. hansenii_. A further analysis revealed that corn starch accumulated aldehydes and ketones, contributing fresh flavor characteristics. Soy protein isolates, through raw material degradation, the synergistic action of _D. hansenii_'s high protease activity, and nitrogen metabolism regulation, increased the total free amino acid content, particularly enhancing umami and sweetness components. It also enriched esters, ketones, and pyrazines, while reducing aldehydes, resulting in a more intense and complex aroma profile. Notably, both carbon and nitrogen sources optimized the fatty acid profile, contributing to the improved nutritional value of the final product. In summary, supplementation with different exogenous carbon and nitrogen sources can regulate the fermentation characteristics of _D. hansenii_ through distinct metabolic pathways, producing differentiated effects in promoting growth and enzyme activity, improving physicochemical properties, and optimizing flavor compound accumulation. The rational selection of carbon and nitrogen sources provides technical support for improving the quality and flavor of fermented sausages, as well as for achieving controlled flavor regulation in fermented meat products. In future studies, the fermentation characteristics of the strain can be further optimized by combining carbon and nitrogen sources and adjusting the carbon-to-nitrogen ratio.  
The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/foods14111840/s1](https://www.mdpi.com/article/10.3390/foods14111840/s1)]([https://www.mdpi.com/article/10.3390/foods14111840/s1](https://www.mdpi.com/article/10.3390/foods14111840/s1)), Table S1. Free Amino Acid Standard Information; Table S2. Free Fatty Acid Standard Information; Table S3. Volatile compound composition and content of fermented sausage culture medium with different carbon and nitrogen sources; Figure S1. Representative chromatograms of free fatty acids in fermented samples from different treatment groups: A, Standard sample; B, control (FCK); C, corn starch (FCC); D, soy protein isolate (FNP).  
**Author Contributions:** Conceptualization, methodology, investigation, writing--original draft, W.D.; supervision, formal analysis, Q.Z.; conceptualization, supervision, writing--review and editing, funding acquisition, J.W. All authors have read and agreed to the published version of the manuscript.  
**Funding:** This study was funded by the National Natural Science Foundation of China (No. 32160607).  
**Data Availability Statement:** The original contributions presented in the study are included in the article, and further inquiries can be directed to the corresponding author.  
**Conflicts of Interest:** The authors declare no conflicts of interest.