Lactic acid production by direct fermentation of agave fructans

BACKGROUND

Lactic acid (LA) is used in various industries and is produced mainly through lactic acid fermentation (LAF). The high cost of glucose, a common substrate, is a major challenge for LA production. Alternatives like fructans from agave are being explored for this purpose, including the production of probiotic beverages using the sap of agave leaves wasted in the field. This study aims to compare the kinetics of LA fermentation using agave fructans and glucose to identify the kinetic factors to be optimize for future use of this process.

RESULTS

The study found that direct fructan fermentation by Lactobacillus bulgaricus delbrueckii (LDF) and Lactobacillus casei (LCF) achieved approximately half the productivity (P = 0.50, 0.59 gL⁻¹/h) as compared to glucose fermentation with the same strains (P = 0.92, 1.33 gL⁻¹/h) apparently because of the delay of fructan hydrolysis. The number of Colony Forming Units (CFU) increased following a logistic function, with a rapid decay observed for pH < 4, following first-order kinetics. Despite the decay, CFU levels remained above 1E7 CFU/mL. This finding could be useful to produce probiotic beverages using agave leaves as a fermentation broth.

CONCLUSION

The LAB strains, Lacticaseibacillus casei NRRL B-441 (LC) and Lactobacillus delbrueckii bulgaricus NRRL B-763 (LD), efficiently utilize commercial agave fructans as the primary carbon source, converting them into LA without prior hydrolysis. Fermentation productivity using fructans was approximately half of that obtained with glucose. This supports using agave fructans and sap for innovative lactic acid fermentations, including probiotic beverages. © 2025 Society of Chemical Industry (SCI).