Lactic acid production from submerged fermentation of broken rice using undefined mixed culture
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The present work aimed to characterize and optimize the submerged fermentation of broken rice for lactic acid (LA) production using undefined mixed culture from dewatered activated sludge. A microorganism with amylolytic activity, which also produces LA, Lactobacillus amylovorus, was used as a control to assess the extent of mixed culture on LA yield. Three level full factorial designs were performed to optimize and define the influence of fermentation temperature (20–50 °C), gelatinization time (30–60 min) and broken rice concentration in culture medium (40–80 g L−1) on LA production in pure and undefined mixed culture. LA production in mixed culture (9.76 g L−1) increased in sixfold respect to pure culture in optimal assessed experimental conditions. The optimal conditions for maximizing LA yield in mixed culture bioprocess were 31 °C temperature, 45 min gelatinization time and 79 g L−1 broken rice concentration in culture medium. This study demonstrated the positive effect of undefined mixed culture from dewatered activated sludge to produce LA from culture medium formulated with broken rice. In addition, this work establishes the basis for an efficient and low-cost bioprocess to manufacture LA from this booming agro-industrial by-product.
KeywordsActivated sludge Broken rice Lactic acid Mixed culture Lactobacillus amylovorus Three-level factorial design
Authors are grateful to the technical staff of Wastewater Treatment Station “Limoeiro” (Presidente Prudente-SP, Brazil) for donation of dewatered activated sludge. The first author thanks Brazilian National Council for Scientific and Technological Development (CNPq/Brazil) for Scientific Initiation Scholarship (PIBIC-2015/UNESP/34044). The corresponding author acknowledges his lovely wife, Relma, and daughters, Giovanna and Paola, for the inspiration to write this manuscript.
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Conflict of interest
The authors declare that they have no conflicts of interest.
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