Lactic acid bacteria are generally fastidious organisms,
which require complex nutrients such as amino acids and vitamins
for cell growth [28].Yeast extract, the most commonly
used nitrogen source, provides complex nutrients for lactic
acid bacteria [2]. To investigate the influence of yeast extract
concentrations on lactic acid fermentation from molasses,
lactic acid fermentations were performed on a jar fermentor
at 38 .C and pH 7.0 using 200 g/l of molasses (equivalent to
102 g/l of total sugar) supplemented with 5.20 g/l of yeast
extract. Fig. 2 shows the time courses of lactic acid production
(Fig. 2a) and cell growth (Fig. 2b) during fermentations
at various concentrations of yeast extract. As shown in Fig. 2,
both the lactic acid production rate and cell growth increased
with the increase of yeast extract concentrations from 5 to
20 g/l. The maximum dry cell weight was obtained to 16.1 g/l
at the medium supplemented with 20 g/l of yeast extract. At
5 g/l of yeast extract, lactic acid fermentation was not completed
even after 90 h of fermentation, and the cell growth
was almost stopped after 10 h of fermentation.
Lactic acid bacteria are generally fastidious organisms,which require complex nutrients such as amino acids and vitaminsfor cell growth [28].Yeast extract, the most commonlyused nitrogen source, provides complex nutrients for lacticacid bacteria [2]. To investigate the influence of yeast extractconcentrations on lactic acid fermentation from molasses,lactic acid fermentations were performed on a jar fermentorat 38 .C and pH 7.0 using 200 g/l of molasses (equivalent to102 g/l of total sugar) supplemented with 5.20 g/l of yeastextract. Fig. 2 shows the time courses of lactic acid production(Fig. 2a) and cell growth (Fig. 2b) during fermentationsat various concentrations of yeast extract. As shown in Fig. 2,both the lactic acid production rate and cell growth increasedwith the increase of yeast extract concentrations from 5 to20 g/l. The maximum dry cell weight was obtained to 16.1 g/lat the medium supplemented with 20 g/l of yeast extract. At5 g/l of yeast extract, lactic acid fermentation was not completedeven after 90 h of fermentation, and the cell growthwas almost stopped after 10 h of fermentation.
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