Liliana Serna Cock1* y Aida Rodríguez de Stouvenel2
Sugar cane (Saccharum officinarum L.) tops and leaves (JCG), and the juice extracted from this sugar cane, harvested with crop burning (JCL) and without crop burning (JCV), were tested as substrates for the discontinuous fermentative production of lactic acid. Anaerobic fermentations were carried out at 32°C, adjusting pH at 6.0, and using Lactococcus lactis subsp. lactis isolated from the same variety of sugar cane. The effect of total sugars and nitrogen concentration on lactic acid production (AL), substrate conversion (CS), yield (Yp/s) and volumetric productivity (rp) were studied for the substrates mentioned above and their mixtures. Lactic acid concentrations up to 70.19 g L-1, CS of 85.46%, Yp/s of 0.88 g g-1 and rp of 0.97 g L-1 h-1 were obtained, with a total sugar concentration of 90 g L-1, from a mixture of JCG and JCV with the addition of 3% (w/v) of yeast extract. Even without the addition of yeast extract, these mixtures performed very well as substrates for lactic acid fermentation (AL: 26.16 g L-1, CS: 67.13%, Yp/s: 0.69 g g-1 and rp:0.55 g L-1 h-1); this is explained in part by the higher nitrogen content of JCG and JCV, compared to JCL. Juice extracted from cane tops and leaves, mixed with cane juice extracted from crops harvested without burning, is a cheap alternative as a raw material for the fermentative production of lactic acid.
Key words: waste products, green cane, lactic acid, cane tops, clean cane, Lactococcus lactis subsp. Lactis.
1 Universidad Nacional de Colombia, Facultad de Ingeniería, A.A 237, Palmira, Colombia. E-mail: firstname.lastname@example.org *Corresponding author.
2 Universidad del Valle, Facultad de Ingeniería, A.A. 25360, Cali, Colombia. E-mail: email@example.com