Contents lists available at ScienceDirect Chemical Engineering & Processing: Process Intensification journal homepage: www.elsevier.com/locate/cep Central composite experimental design applied to evaluate the lactic acid concentration by short path evaporation Andrea Komesu ⁎ , Maria Regina Wolf Maciel, Rubens Maciel Filho School of Chemical Engineering, University of Campinas (UNICAMP), Box: 6066, Zip: 13083-970, Campinas, SP, Brazil ARTICLE INFO Keywords: Lactic acid Fermentation Purification Short path evaporation ABSTRACT In this work, lactic acid purification by short path evaporation (SPE) was evaluated using central composite experimental design. The influences of the evaporator temperature (from 86.7 to 177.3 °C) and condenser temperature (from 7.5 to 24.5 °C) on distilled percentage, and lactic acid purity and recovery at the distillate stream were studied. In the range of study, lactic acid purity obtained at 1 kPa, using evaporator temperature of 86.7 °C and condenser temperature of 16 °C presented the highest lactic acid purity which was about 11 times lactic acid concentration higher than the initial content in raw material. 1. Introduction Lactic acid (LA) is the simplest hydroxyl carboxylic acid with two optically active enantiomers (D(-) and L(+)). It is primarily used for food and pharmaceutical applications, preferentially the L(+) isomer since it is the only LA isomer produced in the human body [1,2]. LA can be used as feedstock to generate multiple commodity and intermediate chemicals [2], such as ethyl lactate, acrylic acid, propylene oxide, acetaldehyde, propanoic acid, and others. It can also be used as a monomer in the preparation of polylactic acid (PLA), biodegradable and biocompatible polymer used for medical applications, in packaging materials, and in mulching films [3]. The LA growing demand for its applications is not been satisfied because of the high cost of LA production and purification processes. Therefore, the development of an efficient and cheap process for LA production and purification is very important. LA can be produced by fermentation or by chemical synthesis. The chemical synthesis is mainly based on the hydrolysis of lactonitrile by a strong acid, where a racemic mixture of the two forms (D(-) and L(+)) LA is produced [4]. Fermentation production of LA has received significant interest, since it is an attractive process in terms of environmental and economic impact, and it is produced an optically pure L- or D-LA which is more valuable than racemic DL-LA, depending on the strain selected [5]. Cheap raw materials, such as starchy and cellulosic materials, whey, and molasses, have been used for lactic acid production [6]. Some industrial waste products, such as sugarcane molasses, are currently receiving a great deal of attention, because it is abundant, renewable, and cheap. In addition, it is an excellent medium of cultivation for fermentation, because of the high sugar content, nitrogen and vitamins. In Brazil, 18 million tons of sugarcane molasses are produced per year by sugar and ethanol sector [7]. The main problem in the production of lactic acid by fermentation is its separation and purification. Therefore, development of an efficient and low cost downstream processing is very important, since this can reach up to 50% of the total cost [8]. Several separation technologies have been reported for lactic acid recovery, such as solvent extraction [9–12], separation with membranes [13–15], reactive distillation [16–19], molecular distillation [20,21], and others. Among these, short path evaporation (SPE) is considered to be an effective separation process for the recovery of lactic acid from fermentation broth without using organic solvents [20,21]. SPE is a thermal separation technique designed especially for heat-sensitive materials. The key features include vacuum condition and very short residence time (seconds) which minimize or eliminate the degradation problems. In previous work [21], our research group studied the influence of operational parameters which could affect the short path evaporation process, such as feed flow rate, agitation, condenser, and evaporator temperature. The results showed that LA with highest purity was obtained at distillate stream. In addition, condenser and evaporator temperature were significant variables of the process. Besides that, linear models used to represent the variation of the distillate percentage and LA purity and recovery at distillate stream were not adequate to fit the experimental data. Therefore, another experimental design was studied in order to develop appropriate models (second-order poly- nomial models) to describe the responses at distillate stream. Bearing all this in mind, the purpose of this work was to optimize the lactic acid purification from fermentation broth by SPE system http://dx.doi.org/10.1016/j.cep.2017.03.020 Received 27 October 2016; Received in revised form 21 March 2017; Accepted 29 March 2017 ⁎ Corresponding author. E-mail address: andrea_komesu@hotmail.com (A. Komesu). Chemical Engineering & Processing: Process Intensification xxx (xxxx) xxx–xxx 0255-2701/ © 2017 Elsevier B.V. All rights reserved. Please cite this article as: Komesu, A., Chemical Engineering & Processing: Process Intensification (2017), http://dx.doi.org/10.1016/j.cep.2017.03.020