## 3 Results and Discussion
### Sugar Profiles of Fermented Samples  
The glucose, lactose, and galactose contents of the products are presented in Table 2B. Glucose is one of the primary carbon sources in LAB metabolism, and its breakdown is crucial for the production of organic acids, especially lactic acid. The LA-p showed the highest glucose consumption (0.674 g/100 mL) accompanied by a significant amount of lactic acid production (0.744 g/100 mL). This observation aligns with the process by which LAB convert glucose to lactic acid through the Embden-Meyerhof pathway [42]. The LB-p also exhibits high glucose consumption (0.672 g/100 mL) and moderate lactic acid production (0.637 g/100 mL). These results reflect its ability to efficiently metabolize glucose to lactic acid and acetic acid (0.523 g/100 mL) [32].  
Lactose is a critical substrate for LAB fermentation, especially in dairy products. Since the initial lactose content of the UHT milk used was between 4.0 and 4.5, the lactose amounts shown in Table 2B were interpreted as the utilization (hydrolysis) of the initial lactose. The hydrolysis of lactose into glucose and galactose provides energy for organic acid production. The LH-p showed the lowest lactose consumption (2.151 g/100 mL), along with moderate lactic acid (0.668 g/100 mL) and citric acid production (0.125 g/100 mL). This indicates that the hydrolysis of lactose plays a central role in the metabolic activity of this strain, providing a balanced organic acid profile for cheese fermentation [37].  
The ST strain also hydrolys a significant amount of lactose (2.085 g/100 mL) and produced moderate lactic acid (0.574 g/100 mL) along with higher citric acid production (0.168 g/100 mL). This is consistent with the lactose hydrolysis and citric acid metabolism in yogurt fermentation [40].  
Galactose is a by-product of lactose hydrolysis and is not metabolized by all LAB strains. The LB strain produces the highest galactose concentration (0.276 g/100 mL), which is associated with moderate lactic acid (0.637 g/100 mL) and acetic acid production (0.523 g/100 mL). This suggests that the _L. bulgarcius_ strain does not efficiently metabolize galactose but, with its heteroferentative capabilities, produces multiple acids from glucose and lactose [42]. The LC strain produced the highest lactic acid content (0.783 g/100 mL) with lower galactose consumption (0.093 g/100 mL). This indicates that _L. casei_ strains are more efficient at converting galactose into lactic acid [29]. The _B. bifidum_ exhibits moderate galactose consumption (0.103 g/100 mL) while producing significant amounts of lactic acid (0.722 g/100 mL) and acetic acid (0.607 g/100 mL) [31].  
Formic acid, although present in small amounts, may originate from the mixed-acid fermentation pathways of LAB. _B. bifidum_ leads in formic acid production (0.164 g/100 mL) and maintains moderate levels of glucose (0.456 g/100 mL) and lactose (1.878 g/100 mL) consumption. This is consistent with the heteroferentative nature of _B. bifidum_[35]. _L. bulgarcius_ also produces high levels of formic acid (0.163 \(\pm\) 0.014) and consumes significant amounts of galactose (0.276 g/100 mL). Strains like _L. casei_ and _L. acidophilus_ efficiently metabolize glucose and galactose to lactic acid, while _B. bifidum_ and _S. thermophilus_ produce a more balanced acid profile.