Biochemical Engineering Journal 68 (2012) 109–113 Contents lists available at SciVerse ScienceDirect Biochemical Engineering Journal journa l h omepage: www.elsevier.com/locate/bej Regular article Microalgae (Nannochloropsis salina) biomass to lactic acid and lipid Md. Mahabubur Rahman Talukder ∗ , Probir Das, Jin Chuan Wu Institute of Chemical and Engineering Sciences, 1 Pesek Road, Jurong Island, Singapore 627833, Singapore a r t i c l e i n f o Article history: Received 5 January 2012 Received in revised form 22 June 2012 Accepted 1 July 2012 Available online 22 July 2012 Keywords: Lactic acid Microalgae Lipid Ion-exchange Lactobacillus pentosus a b s t r a c t A method for lactic acid production and lipid extraction from microalgae (Nannochloropsis salina) biomass was investigated. Microalgae biomass was acid (5% H 2 SO 4 ) hydrolyzed at 120 ◦ C for 1 h, and subsequently treated with hexane at 40 ◦ C and 200 rpm to separate lipid from the hydrolysate. The sugar (glucose plus xylose) yield reached 64.3% and remained the same until the biomass loading of 15% (w/v) after which, it dropped. Lipid free hydrolysate was neutralized and used as fermentation medium for Lactobacillus pentosus for lactic acid production. Lactic acid yield reached 92.8% at sugar 3–25 g/l, 30 ◦ C and shaking speed 150 rpm under anaerobic condition. The acid hydrolysis facilitated lipid extraction from microalgae biomass, and lipid yields with and without acid hydrolysis were 85.6% and 48.7%, respectively. Results sug- gest that the developed method can be successfully applied in lipid extraction and lactic acid production from microalgae biomass. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Oleaginous phototrophic microalgae are sunlight-driven cell factories that convert carbon dioxide to lipids. These microorgan- isms have received much attention in lipid production and CO 2 mitigation. The lipid content in oleaginous microalgae is typi- cally 20–40%, but it may be as high as 70% of dry biomass [1–4]. Microalgal lipid production system generates large amounts of lipid depleted biomass, which contains polysaccharides, proteins, phos- phate, vitamins and minerals. Lipid-deplete biomass can, therefore, be a suitable feedstock for fermentative production of many chemi- cals such as ethanol, butanol and lactic acid. Compared with ethanol and butanol, lactic acid has a broader range of applications in the food, textile, pharmaceutical, cosmetic and chemical industries because of its multi-functional properties. It is used as acidifier, fla- voring agent and preservative of processed foods. Currently, there is an increased demand for lactic acid as a feedstock for the pro- duction of biopolymer poly-lactic acid (PLA). PLA has many uses in surgical sutures, orthopedic implants, drug delivery systems, and disposable consumer products. However, high cost of raw materi- als, e.g. starch and refined sugars, which accounts for the highest portion of the production cost, represents one of the most serious obstacles for cost effective fermentative production of lactic acid. Therefore, the main objective of this study is to investigate the fea- sibility of utilizing lipid free microalgae hydrolysate as a feedstock ∗ Corresponding author. Tel.: +65 67963826; fax: +65 63166182. E-mail address: talukder@ices.a-star.edu.sg (Md.M.R. Talukder). for fermentative production of lactic acid. Prior to lactic acid fer- mentation, the microalgae biomass needs to be processed in order to extract lipid and release sugar. Chloroform–methanol or chloroform–methanol–water has been widely used for lipid extraction from microalgae [5–8]. While these methods are effective, large scale lipid extraction using chloroform is precluded by environmental and health risks. Fur- thermore, these methods produce non-lipid contaminants that inhibit the downstream processing of lipid to others products. Hex- ane, despite being reported to be less efficient than chloroform, is less toxic and has minimal affinity toward non-lipid contaminants [9,10]. The improvement in hexane extraction of lipid is, therefore, needed to make microalgal lipid commercially competitive. In this study, microalgae biomass was acid hydrolyzed and the hydrolysate was subsequently treated with hexane to extract lipid. Effects of different parameters on the production of lactic acid by fermentation of the hydrolysate were investigated. Lactic acid yield and volumetric productivity obtained using the microalgae hydrolysate were compared with those obtained using a reference MRS medium. 2. Materials and methods 2.1. Microalgae biomass Microalgae (Nannochloropsis salina) biomass (dry) was kindly provided by Solix Biofuel Inc. The total lipid and sugar content in the biomass were determined according to the method of Brown [4], and found to be 39.8% and 18.2% of dry biomass, respectively. 1369-703X/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.bej.2012.07.001