Lactic acid production by a strain of Lactococcus lactis subs lactis isolated from sugar cane plants

A Lactococcus lactis subs lactis strain was selected from 20 lactic acid strains isolated from the leaves of sugar cane plants, variety CC 85-92. The effects of substrate concentration and pH control on lactic acid (LA) production, glucose conversion (GC) and yield (Yp/s) were investigated using this strain. In batch fermentation at 32\ub0C, with 60 gl-1 of glucose and a pH of 6.0, concentrations of up to 35 gl-1 of lactic acid were obtained. Maximum production and glucose conversion was achieved at low glucose concentrations. The strain shows great potential for lactic acid production from glucose, even without using pH control during fermentation (13.7 gl-1)

Producci\uf3n econ\uf3mica de \ue1cido l\ue1ctico utilizando residuos de cosecha y jugos de ca\uf1a de az\ufacar ( Saccharum officinarum L. )

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\ub0C, 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% (p/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.Para la producci\uf3n fermentativa discontinua de \ue1cido l\ue1ctico, se evaluaron como sustratos los jugos de cogollos y hojas (JCG) de la ca\uf1a de az\ufacar (Saccharum officinarum L.) y los jugos extra\ueddos de esta ca\uf1a, cosechada con quema (JCL) y sin quema (JCV). Las fermentaciones se realizaron anaer\uf3bicamente, a 32\ub0C, con ajuste de pH a 6,0 y usando Lactococcus lactis subsp. lactisaislado de cultivos de la misma variedad. Para los sustratos mencionados y sus mezclas se estudi\uf3 el efecto de la concentraci\uf3n de az\ufacares totales y de nitr\uf3geno sobre la producci\uf3n de \ue1cido l\ue1ctico (AL), la conversi\uf3n de sustrato (CS), el rendimiento (Yp/s) y la productividad volum\ue9trica (rp). Se obtuvieron concentraciones de \ue1cido l\ue1ctico por encima de 70,19 g L-1, CS de 85,46%, Yp/s de 0,88 g g-1 y rp de 0,97 g L-1 h-1 con una concentraci\uf3n de 90 g L-1 de az\ufacar total usando una mezcla de JCG y JCV con adici\uf3n de 3% (p/v) de extracto de levadura. A\ufan sin adici\uf3n de extracto de levadura, estas mezclas presentaron muy buen comportamiento como sustrato de fermentaci\uf3n \ue1cido l\ue1ctica (AL: 26,16 g L-1, CS: 67,13%, Yp/s: 0,69 g g-1 y rp: 0,55 g L-1 h-1); este comportamiento se explica en parte por el mayor contenido en nitr\uf3geno del JCG y del JCV, comparado con el JCL. El jugo extra\ueddo de las hojas y cogollos, mezclado con el jugo extra\ueddo de la ca\uf1a cosechada sin quemar es una alternativa barata como materia prima para la producci\uf3n fermentativa de \ue1cido l\ue1ctico