A Plackett-Burman design for substituting mrs medium components with avocado seed hydrolysate for growth and lactic acid production by Lactobacillus sp.

Lactic acid is a platform chemical with many commercial applications. Even though the biotechnological production is the leading approach, medium cost is a serious bottleneck. Starch from agroindustrial residues, such as avocado seeds, stands out as a promising feedstock. A Plackett-Burman design was used for screening and selection of MRS medium components that could be substituted with avocado seed hydrolysate (ASH) for growth and lactic acid production by Lactobacillus sp. The screening was performed using 20 g/L initial reducing sugars from the ASH; then, the effect of an increasing carbon-source concentration was evaluated. Five out of nine components could be substituted from the MRS medium for lactic acid production; this represented a medium cost reduction of at least 17 %. Peptone from casein (10 g/L), meat extract (8 g/L), yeast extract (4 g/L), and sodium acetate (5 g/L) had to be maintained. The highest lactic acid concentration was estimated at 5.7 ± 0.7 g/L, achieved at 40.0 ± 2.0 g/L initial reducing sugar in experiments carried out in a stirred tank bioreactor, despite the presence of some inhibitory growth effects. Kinetic parameters were also obtained. This study may serve as a starting point for further research since this is the first study reported in the literature exploring the production of lactic acid from ASH as a feedstock.

Keywords: lactic acid, Lactobacillus sp., avocado seed hydrolysate; Plackett-Burman design.