L-lactic acid production process development obtained from sugars fermentation: kinetic data obtaining and separation processes evaluation

Author(s)

Ana Lívia Chemeli Senedese

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia Química
• Defense date: 2016-02-25

Examining board members

Maria Regina Wolf Maciel; Jorge Vicente Lopes da Silva; Cecília Amélia de Carvalho Zavaglia; Melina Savioli Lopes; Viktor Oswaldo Cárdenas Concha

• Advisor: Rubens Maciel Filho; Maria Regina Wolf Maciel

Abstract

The use of alternative substrates in biotechnological fermentations is a viable alternative to substitute those derived from non-renewable sources. The molasses is an example and can be used to produce L-lactic acid that has shown to be promising to produce poly-L-lactic acid (PLLA) for application in medical field. For this work, three L-lactic acid producing bacteria and also molasses consumers were selected from literature for shaker trials: Lactobacillus (L.) rhamnosus ATCC 7469, L. rhamnosus ATCC 10863 and L. delbrueckii ATCC 9649. Through a star configuration 23 experimental planning, the bacterium that produced more L-lactic acid was selected, which was the L. rhamnosus ATCC 10863, producing 16.5 g/L. The operation conditions were 43? C as temperature and concentrations of 27.6 g/L of sucrose (sugar with higher percentage at molasses) and 3.0 g/L of yeast extract, respectively. The sugars behavior showed that glucose and fructose were basically completely consumed while sucrose was barely consumed. At bioreactor, that bacterium with the operation conditions just mentioned, besides the pH 5.0, was used at two fed batch fermentation processes (processes 1 and 2) and two batch fermentation processes (processes 3 and 4) with the molasses without pre-treatment (virgin). Among these processes, the sucrose was still scarcely consumed, reaching the maximum of 22.5 % at fed batch process 1. At this same process, the maximum of fructose was converted, 98.4 %, and the maximum of glucose converted was at batch process 4, 91.7 %, The maximum peak of L-lactic acid produced was at fed batch process 2, 22.0 g/L. Thus, after, it was performed another batch fermentation process (process 5) with molasses pre-treatment, the sucrose hydrolysis into glucose and fructose using the enzyme invertase, resulting in 100 %. At fermentative process 5, the glucose was converted in 98.2 % and fructose in 99.3 %, generating 35.5 g/L of L-lactic acid (maximum peak). The maximum productivity was 2.0 g/Lh, the biomass growth was 5.0 g/L, the yield was 97.5 % and it was detected 98.5 % of the isomer L(+) of lactic acid at fermentation broth at the end of process. Therefore, this process was identified as the "optimum" of this work. Afterwards, the L-lactic acid separation process was done at the high performance liquid chromatography (HPLC) equipment with fraction collector. It was used the semi-preparative column ZORBAX Eclipse XDB-C18 to separate the L-lactic acid from all components remained at fermentation broth, but the acetic acid at the enzymatic solution previously used was collected at the same time. Subsequently, it was used the analytical column Aminex HPX-87H that isolated and collected the L-lactic acid, obtaining 11 mL of solution of mobile phase and diluted acid, with recovery rate of 53.0 %. Intending to demonstrate the viability of use of this technique to separate L-lactic acid from fermentation, this methodology was valid (AU)

• FAPESP's process: 11/11742-2 - L-lactic acid production process development obtained from sugars fermentation: kinetic data obtaining and separation processes evaluation
• Grantee: Ana Lívia Chemeli Senedese
• Support Opportunities: Scholarships in Brazil - Doctorate