INGREDIENT SELECTION FOR PLASTIC COMPOSITE SUPPORTS FOR L-(-LACTIC ACID BIOFILM FERMENTATION BY LACTOBACILLUS-CASEI SUBSP RHAMNOSUS())

Plastic composite supports containing 50% agricultural products (oat h ulls, soybean hulls, yeast extract, soybean flour, dried bovine erythr ocytes, bovine albumin, and/or mineral salts) and 50% (wt/wt) polyprop ylene were produced by high-temperature twin-screw extrusion, The rese arch employed two half sets of a five-factorial fractional design (2(5 -1)) to evaluate the effects of different agricultural components on t he properties of the plastic composite supports and to select the best plastic composite support formulation for lactic acid fermentation, T he biofilm population was affected by the contact angle and relative h ydrophobicity of the supports (r = 0.79 to 0.82), Lactic acid was prod uced by the suspended cells (r = 0.96) and the biofilm on the plastic composite support discs (r = 0.85), Incorporation of yeast extract int o plastic composite supports enhanced growth of free and attached cell s in minimal medium (P < 0.0001). The presence of soybean hulls, yeast extract, or mineral salts in plastic composite supports produced less hydrophobic supports (P < 0.0001) and enhanced cell attachment (P < 0 .03), Under all conditions, suspended-cell and polypropylene disc cont rols gave negligible lactic acid production and cell density, Plastic composite supports containing soybean hulls, yeast extract, soybean fl our, bovine albumin, and mineral salts gave the highest biofilm popula tion (2.3 x 10(9) CFU/g of support), cell density (absorbance of 1.8 a t 620 nm), and lactic acid concentration (7.6 g/liter) in minimal medi um.