REDUCTION OF COSTS IN NISIN PRODUCTION USING DILUTED SKIMMED MILK IN BIOREACTOR

Luciana Juncioni de Arauz (FCF/USP); Angela Faustino Jozala (FCF/USP); Priscila Gava Mazzola (FCM/UNICAMP); Júlia Baruque-ramos (EACH/USP); Adalberto Pessoa Júnior (FCF/USP); Thereza Christina Vessoni Penna (FCF/USP)

Nisin is widely used natural food preservative due to its antimicrobial activity and has potential applications in numerous fields (pharmaceutical, veterinary and health care products). However, the high cost of producing nisin by batch cultures of L. lactis, is a limiting factor. This study aims to optimize large-scale nisin production utilizing diluted skimmed milk as alternative growth media to reduce process costs and stimulate its use. Lactococcus lactis subsp. lactis ATCC 11454 precultures were growth in 150 mL MRS broth for 36 h at 30ºC. It was poured into 1500 mL of diluted skimmed milk with 25% of standard concentration (2.27 g _{total solids}) in 2L bioreactor (New Brunswick Scientific), at 30ºC for 52 h. The operation conditions were, 100 or 200 rpm, and 0.5 L. min^-1 air flow or without air injection. The nisin activity expressed in culture media was quantified by agar diffusion assay, utilizing Lactobacillus sakei ATCC 15521 as sensitive indicator microorganism. The highest and the lowest nisin activity were detected in conditions with 0.5 L.min^-1 air injection: (i) 100rpm, after 16 h (8.38x10³ AU.mL^-1) of cultive, (ii) 200rpm, after 20h (1.04x10³ AU.mL^-1) of microbial growth. On the other hand, the assays without air injection reached the best nisin activity after 36 h/100rpm (2.0x10³ AU.mL^-1) and 12 h/200rpm (2.88x10³ AU.mL^-1) of batch cultures. The results showed that the dilution of skimmed milk supplied nisin expression from cells into media in a short-time process (16h). From an industrial point of view, diluted skimmed milk can be used as an alternative economical medium for production of this biomolecule high value-added.