Lactic acid bacteria (LAB) have been documented as potential vitamin B12 producers and may constitute an exogenous source of cobalamin for the microalga Chlorella vulgaris, which has been described as being able to perform vitamin uptake. Hence, there is an interest in discovering novel B12-producing probiotic LAB. Therefore, the purpose of the current work was to perform a phenotype–genotype analysis of the vitamin B12 biosynthesis capacity of LAB isolated from C. vulgaris bioreactors, and investigate their probiotic potential. Among the selected strains, Lactococcus lactis E32, Levilactobacillus brevis G31, and Pediococcus pentosaceus L51 demonstrated vitamin B12 biosynthesis capacity, with the latter producing the highest (28.19 ± 2.27 pg mL⁻¹). The genomic analysis confirmed the presence of pivotal genes involved in different steps of the biosynthetic pathway (hemL, cbiT, cobC, and cobD). Notably, P. pentosaceus L51 was the only strain harboring cobA, pduU, and pduV genes, which may provide evidence for the presence of the cobalamin operon. All strains demonstrated the capability to withstand harsh gastrointestinal conditions, although P. pentosaceus L51 was more resilient. The potential for de novo cobalamin biosynthesis and remarkable probiotic features highlighted that P. pentosaceus L51 may be considered the most promising candidate strain for developing high-content vitamin B12 formulations.

Phenolic diterpene carnosic acid (CA) is widely used in the food, nutritional health, and cosmetic industries due to its antioxidative and antimicrobial properties. This work aimed to overproduce CA in Saccharomyces cerevisiae from sugarcane syrup in fed-batch 2 L bioreactor fermentation. A geranylgeranyl diphosphate (GGPP)-producing strain modified with genes encoding the enzymes copalyl diphosphate synthase (Pv.CPS), miltiradiene synthase (Ro.KSL2), hydroxy ferruginol synthase (Ro.HFS), CA synthase (Ro.CYP76AK8), CYP reductase (At.ATR1), and transketolase (TKL1) was used. Lowering the feed rate from 12–26 g/L/h to 7–8 g/L/h, and the use of a dynamic dissolved oxygen (DO) trigger (min. 10%, max. 40%, threshold 70%) instead of a DO trigger of 30%, enhanced CA production by 27%. As a result, the highest CA titer ever reported to date, 191.4 mg/L, was obtained in 4-day fermentation. This study shows the feasibility of engineered yeast to produce CA from the sustainable feedstock sugarcane syrup.