## 2 Results and Discussion
### VOCs Produced during Fermentation
Overall, the glucose-containing defined medium (DM) showed higher concentrations of VOCs (\(m/z\)) of interest after fermentation by LB672 compared to the fructose-containing defined medium (DMFr) at either 25 or 35 \({}^{\circ}\)C. Among the detected fermented VOCs in the DM, acetaldehyde, methanethiol, and benzeneacetaldehyde are key VOCs in dairy products [49; 52], and methanethiol is a key VOC in meat products [51]. Though LB672 grew well in the defined medium DMFr, the concentrations of VOCs detected in this study were low. It has previously been reported that mannitol (sugar alcohol) was the main compound produced by _Lim. fermentatum_ growing in the medium containing fructose, whereas ethanol was the main compound in the medium containing glucose [24]. Note, however, that the low concentration of ethanol produced in the defined medium DMFr, in the current study, could be a benefit for developing low-ethanol containing plant-based fermented foods or ingredients. It was of interest that the concentrations of specific VOCs were higher at 35 \({}^{\circ}\)C compared to 25 \({}^{\circ}\)C, despite the actual growth of LB672, based on OD\({}_{600}\) values being higher at 25 \({}^{\circ}\)C compared to 35 \({}^{\circ}\)C. This observation suggests that temperature influenced the metabolic processes of LAB, which in turn impacted on the production of VOCs. It is important to appreciate that many other compounds in the defined medium are likely to impact on VOC production [13; 58; 59; 60; 61; 62]. Therefore, the production of specific VOCs that mimic meat or dairy flavours by LB672 will be better understood by examining other medium compositions in the defined medium using a similar experimental design. Figure 3. The proposed metabolic pathways of LB672 fermentation in the defined medium contained glucose and an amino acid mixture (DM). Dotted lines indicate a series of enzymatic or chemical reactions. Adapted from [PERSON] and [PERSON] [15], [PERSON] et al., [43], [PERSON] and [PERSON] [46], [PERSON] et al. [47], [PERSON] [48], [PERSON] and [PERSON] [54], [PERSON] et al. [56], [PERSON] and [PERSON] [57], TC: Phosphobelotolase, ALDH: Alcohol dehydrogenase, LDH: Lactate dehydrogenase, ODC: Ocaloacetate decarboxylase, AK: Acetokinase, TA: threonine aldolase, SHMT: serine hydroxymethyltransferases, PDC: Pyruvate decarboxylase, TPP: Thiamine pyrophosphate, ALS: \(\alpha\)-Acetolacate synthase, ALDC: \(\alpha\)-Acetolacate decarboxylase, DAR: Diacetyl] aceton reductase, BDH: 2,3-butanediol dehydrogenase, CBL: cystathioneine \(\beta\)-lysse, CCL: cystathioneine \(\gamma\)-lysse, and DC: decarboxylase. Figure 4: Mean concentrations (ppbV) of \(m/z\) 45.033 (i.i. acetaldehyde) (a) \(m/z\) 49.011 (i. methanethiol) (b) \(m/z\) 89.060 (i. ethyl acetate) (c) \(m/z\) 91.027 (i.e. methyl thioacetate/mercaptoethanol) (d) \(m/z\) 91.072 (i.i. 23 botanicalio) (e) and \(m/z\) 121.057 (i. benzereacetaldehyde) (f) across defined medium compositions (DM: glucose added, DMF: fructose added) at 25 (\(\blacksquare\)) and 35 (\(\blacksquare\)) \({}^{\circ}\)C after 7 days of fermentation by 1B672. Values are presented as mean \(\pm\) standard error (\(n=4\)). Different superscript lowercase letters represent significant difference between the carbon sources at either 25 or 35 \({}^{\circ}\)C according to [PERSON]’s test at \(p<0.05\).