Experimental evaluation of alternative fermentation media for L-lactic acid production from apple pomace
2008
Gullón, Beatriz | Alonso, José Luis | Parajó, Juan Carlos
BACKGROUND: A variety of nitrogen sources were tested for lactic acid production. Corn steep liquor is a low-cost by-product that could replace some of the expensive nutrients of the general lactobacilli media. This work deals with the optimisation of the composition of a low-cost medium for lactic acid production from apple pomace by Lactobacillus rhamnosus CECT-288.RESULTS: Corn steep liquor (CSL) and yeast extract (YE) were evaluated as nutrient sources for lactic acid production from apple pomace. In comparison with media containing CSL, experiments with YE led to higher volumetric productivities but lower lactic acid concentrations and product yields. The presence of YE increased the production of acetic acid. In media containing 0.2 g CSL g⁻¹ potential sugars, 29.5 g lactic acid L⁻¹ was obtained after 24 h, at good yield (35.5 g per 100 g dry apple pomace) and productivity (1.23 g L⁻¹ h⁻¹), with a lactic acid/acetic acid mass ratio of 98 g g⁻¹.CONCLUSION: The experimental results proved that CSL is a suitable nutrient source for lactic acid production from apple pomace, even though the volumetric productivity was lower than in experiments employing YE. Considered as a nutrient supplement, CSL presents advantages over YE not only in terms of cost but also in terms of product yield, final lactic acid concentration and lactic acid/acetic acid mass ratio. The utilisation of apple pomace as the raw material and CSL as the sole nutrient source (both cheap by-products) enables the production of lactic acid by an economical, environmentally friendly process.
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