Short Communication Zizyphus oenophlia: A potent substrate for lactic acid production Moumita Bishai a , Swarnalok De a , Basudam Adhikari b , Rintu Banerjee a,⇑ a Microbial Biotechnology and Downstream Processing Laboratory, Agricultural and Food Engineering Department, Indian Institute of Technology, Kharagpur 721 302, India b Materials Science Centre, Indian Institute of Technology, Kharagpur 721 302, India article info Article history: Received 12 August 2012 Received in revised form 6 December 2012 Accepted 8 December 2012 Available online 17 December 2012 Keywords: Lactic acid Zizyphus oenophlia Response surface methodology Circular dichroism Direct polycondensation abstract The objective of the present investigation deals with optimization of L-lactic acid production from Zizy- phus oenophlia, a potential low cost substrate. Central composite design (CCD) based on response surface methodology (RSM) was employed as a statistical tool to investigate the effect of substrate: media ratio, temperature, pH and inoculum volume on lactic acid production. Under optimum condition, the exper- imental yield was 95.09%, which matched well with the predictive yield of 95.45%. HPLC and circular dichroism (CD) analysis of the fermented product was carried out to confirm the presence of lactic acid in its L (+) seriospecificity respectively. For application of lactic acid in biotechnological sector polymer- ization studies were carried out. The PLA upon recovery through direct polycondensation reaction resulted in the yield of 85%. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Renewable resources are the natural resources which can be reproduced through biological or natural processes and replen- ished with time. Owing to rapid population expansion and indus- trial boom, today’s world is facing huge challenges regarding fast depletion of non-renewable resources as well as accumulation of refractory substances causing environmental pollution. Their replacement by renewable resources is recognized as a newer wave for the production of value added products having high mar- ket value. As they are the part of our natural ecosystem, such re- sources are not only environment friendly, but also reduce the cost of the product to a greater extent. Lactic acid, being one of the important metabolite of living system, owes a distinctive posi- tion in the family of organic acids. It is generally recognized as safe product (GRAS). It attracts much attention due to its wide-range application as food stabilizer, pharmaceutical adjuvant and also an intermediate for the production of polylactic acid (PLA) (Laopai- boon et al., 2010). Chemical synthesis provides lactic acid in race- mic form having L-lactic acid and D-lactic acid. Whereas, biotechnological process can produce pure form of stereoisomers of lactic acid depending on the type of organism used for produc- tion (John et al., 2007; Meng et al., 2012). As human beings have L-lactate dehydrogenase capable of metabolizing L-lactic acid only, it is the preferred isomer in food and pharmaceutical industries (Naveena et al., 2005). High product specificity, mild production condition, low energy consumptions etc., are the advantages of adopting a biotechnolog- ical method for lactic acid production (John et al., 2007), while uti- lization of cheap carbon sources such as starchy raw materials can be considered an effective approach for cost reduction (Yumoto and Ikeda, 1995). Zizyphus oenophlia (vernacular name: Siakul) is a shrub distributed throughout the warm temperate and subtrop- ical regions of the world. They accumulate organic substances such as starch, protein, cellulose, phenolics and flavonoids which de- picts its therapeutic potential (Muchuweti et al., 2005). Z. oenoph- lia, due to its appreciable amount of starch content and cosmopolitan accessibility could be considered as an inexpensive renewable raw material suitable for fermentation process. Lactobacillus amylophilus GV6 has been reported to have the po- tential of directly fermenting starch to lactic acid (Vishnu et al. 2000). Its amylolytic enzymes play an important role in the degra- dation of starch and subsequent conversion to lactic acid. In the present study an attempt was taken to exploit Z. oenoph- lia as a source of starch for production of lactic acid by the strain L. amylophilus GV6. RSM (Naveena et al., 2004; Kuila et al., 2011) was employed for the statistical optimization of lactic acid production. Further the purified lactic acid was applied for synthesis of polylac- tic acid. 2. Methods 2.1. Substrate Zizyphus fruits were collected locally from farms of Agricultural and Food Engineering Department of IIT Kharagpur. The air dried 0960-8524/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.biortech.2012.12.049 ⇑ Corresponding author. Tel.: +91 3222 283104; fax: +91 3222 282244. E-mail address: rb@iitkgp.ac.in (R. Banerjee). Bioresource Technology 133 (2013) 627–629 Contents lists available at SciVerse ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech