## 4 Conclusions  
Yeast plays an important role in the fermentation process and biosynthesis of aroma compounds. Thanks to their metabolic abilities, it is possible to valorise waste plant materials and obtain valuable compounds by fermentation. This study proves the possibility of using unconventional yeasts to produce volatile compounds during the fermentation of apple pomace. The previous adaptation of yeast to a temperature of 15 \({}^{\circ}\)C enabled the use of these microorganisms for low-temperature biological processes. The conducted investigation of apple pomace valorisation by fermentation with non-_Saccharomyces_ yeast at the temperature of 15 \({}^{\circ}\)C allowed us to draw the following conclusions:  
* The use of commercial enzymatic preparations enabled satisfactory liquefaction of apple pomace, but enzymatic hydrolysis did not make the microbial growth process more efficient.
* The ability of the tested yeast to produce volatile organic compounds during the fermentation of both untreated and hydrolysed apple pomace was confirmed.
* The higher the inoculum size was, the greater biomass growth was observed. However, in the model experiment, a larger amount of inoculum did not make the biosynthesis of volatile organic compounds more efficient.
* _Hanseniospora avarum_ D9 produced the highest amounts of volatile organic compounds during the fermentation of untreated and hydrolysed apple pomace. However, a significant increase in the higher alcohols content was observed in the hydrolysed medium.  
The following supporting information can be downloaded at [[https://www.mdpi.com/article/10.3390/app15052726/s1](https://www.mdpi.com/article/10.3390/app15052726/s1)]([https://www.mdpi.com/article/10.3390/app15052726/s1](https://www.mdpi.com/article/10.3390/app15052726/s1)), Supplementary report S1_Apple_pomace_1_10; Supplementary report S2_Apple_pomace_9_10; Supplementary report S3_Apple_pomace_11_10; Supplementary report S4_Apple_pomace_hydrolysate_1_10; Supplementary report S5_Apple_pomace_hydrolysate_9_10; Supplementary report S6_Apple_pomace_hydrolysate_11_10.  
Conceptualization, W.L., I.M. and J.B.; methodology, W.L., K.P.-P. and S.M.; validation, I.M. and J.B.; formal analysis, K.P.-P.; investigation, W.L., J.D. and S.M.; resources, I.M.; data curation, W.L.; writing--original draft preparation, W.L. and J.D.; writing--review and editing,W.L., I.M. and J.B.; supervision, J.B.; funding acquisition, J.B. All authors have read and agreed to the published version of the manuscript.  
This work was supported by the Wojewodzki Fundusz Ochrony Srodowiska i Gospodarki Wodnej w Lodzi (Grant no. 157/BN/D/2020).  
DNA sequences (Genbank accessions OQ275007.1, OQ275152.1, and OQ275025.1) and the initial characterisation of cold-adapted isolated yeast are available online at [[https://bioresources.cn.rncsu.edu/resources/plant-biomass-as-a-source-of-low-temperature-yeasts/](https://bioresources.cn.rncsu.edu/resources/plant-biomass-as-a-source-of-low-temperature-yeasts/)]([https://bioresources.cn.rncsu.edu/resources/plant-biomass-as-a-source-of-low-temperature-yeasts/](https://bioresources.cn.rncsu.edu/resources/plant-biomass-as-a-source-of-low-temperature-yeasts/)) (accessed on 25 February 2025).  
This research was completed while the first author was a doctoral candidate at the Interdisciplinary Doctoral School at the Lodz University of Technology, Poland. The authors thank [PERSON] for his collaboration regarding the English language revision of this manuscript. The authors declare no conflicts of interest.  
The following abbreviations are used in this manuscript:  
VOCSAVolatile organic compounds  
APApple pomace  
H-APHydrolysed apple pomace