Cheese whey based lactic acid production in stirred tank reactor by Lactobacillus casei ccpA global regulator mutant

LEGISA DANILO; BLASCO MARTÍN; CATONE MARIELA; RUZAL SANDRA M; PALOMINO MARÍA MERCEDES; ALLIEVI MARIANA CLAUDIA

Simposio; V INTERNATIONAL SYMPOSIUM ON LACTIC ACID BACTERIA BENEFITTING FROM LACTIC ACID BACTERIA PROGRESS IN HEALTH AND FOOD; 2016

CERELA

Lactic acid bacteria (LAB), such as Lactobacillus casei, are microorganisms whose metabolism is strictly fermentative with high nutritional requirements. The carbohydrate metabolism of LAB produces lactate as major product. Lactic acid is widely used in wide range of industries, and much work has been done to improve the production of lactate in a cheap and energy-saving process, including bioprocess optimization and genetic modification of strains. The efficient use of nutrients is associated with carbon catabolite repression (CCR), which allows microbes to select their preferred source from multiple offerings of carbon catabolites. The catabolite control protein A (CcpA) is a mediator of CCR in Gram-positive bacteria. CcpA participates in the induction of genes of basic metabolism, including nitrogen metabolism, and then it is considered a global regulator. In this context, we assessed the lactic acid production from cheese whey based medium by Lactobacillus casei BL23 strain (a Generally Recognized as Safe organism) and its ccpA mutant (BL71), to evaluate the effect of ccpA mutation in the lactic acid production. The lactate production was performed in a 5 L stirred tank reactor using a batch fermentation strategy from cheese whey conditioned with yeast extract and salts. Preliminary experiment in MRS broth using batch strategy was used to determine the kinetic parameters by measuring OD 600nm, dry weight (DW) and CFU mL-1. The MRS medium μmax for BL71 were consistently higher than for BL23 strain (μmax DW 0.24 h-1 for BL23 and 0.42 h-1 for BL71). The 48 h cumulative base consumption was used as an indicator of the ability to produce acidic compounds, being 630 and 12 mmol of NH4OH of per liter of culture for BL71 and BL23, respectively. The lactic acid production from BL23, at this time, was 2.42 g L-1, meanwhile the BL71 strain produced 19.33 g L-1, almost 8-fold more for the later. This parameter coincides with the higher value on CFU mL-1 (4.36 x 109 for BL71 and 8.9 x 108 for BL23). The cumulative production of lactate until the end of the fermentation (56 h for BL71 and 78 for BL23) were equal to 37 g L-1 for both strains. Thus, in the culture conditions used, the ccpA mutation increases the productivity of lactate from 0.174 to 0.82 g L-1 h at 54 h of culture (the peak production of lactate for BL71). Considering the different values observed for the µ between MRS and cheese whey based medium, we will optimized the culture medium for both strains in order to assess the productivity in optimal culture conditions. Considering the preliminary results obtained, LAB´s ccpA mutants could be an excellent candidate for future technological developments, enabling the production of lactic acid in an effective and unexpensive way, using cheese whey as carbon sources from dairy industrial wastes.