Research review paper Direct lactic acid fermentation: Focus on simultaneous saccharification and lactic acid production Rojan P. John a,b, ⁎, G.S. Anisha a,c , K. Madhavan Nampoothiri a , Ashok Pandey a a Biotechnology Division, National Institute for Interdisciplinary Science and Technology, CSIR, Thiruvananthapuram - 695 019, Kerala, India b Institut national de la recherche scientifique-Eau Terre Environnement, 490, rue de la Couronne, Québec (QC), G1K 9A9, Canada c Department of Zoology, Government College, Chittur, Palakkad, Kerala, India abstract article info Article history: Received 21 August 2008 Received in revised form 16 October 2008 Accepted 18 October 2008 Available online 31 October 2008 Keywords: Lactic acid Simultaneous saccharification fermentation Biomass Direct lactic acid production In the recent decades biotechnological production of lactic acid has gained a prime position in the industries as it is cost effective and eco-friendly. Lactic acid is a versatile chemical having a wide range of applications in food, pharmaceutical, leather and textile industries and as chemical feedstock for so many other chemicals. It also functions as the monomer for the biodegradable plastic. Biotechnological production is advantageous over chemical synthesis in that we can utilize cheap raw materials such as agro-industrial byproducts and can selectively produce the stereo isomers in an economic way. Simultaneous saccharification and fermentation can replace the classical double step fermentation by the saccharification of starchy or cellulosic biomass and conversion to lactic acid concurrently by adding inoculum along with the substrate degrading enzymes. It not only reduces the cost of production by avoiding high energy consuming biomass saccharification, but also provides the higher productivity than the single step conversion by the providing adequate sugar release. © 2008 Elsevier Inc. All rights reserved. Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145 2. Developments in lactic acid production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146 3. Raw materials for lactic acid production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146 4. Lactic acid fermentation processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147 5. Direct lactic acid fermentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148 5.1. Direct fermentation with amylolytic lactic acid bacteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148 5.2. Fungal system for direct lactic acid fermentation of complex substrates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 5.3. Direct lactic acid production by simultaneous saccharification and fermentation . . . . . . . . . . . . . . . . . . . . . . . . . . 149 5.3.1. Incubation temperature reduction in simultaneous saccharification and fermentation . . . . . . . . . . . . . . . . . . . . 149 5.3.2. Sugar concentration in simultaneous saccharification and fermentation . . . . . . . . . . . . . . . . . . . . . . . . . . 149 5.3.3. Role of enzyme in simultaneous saccharification and fermentation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 5.3.4. Effect of product concentration in simultaneous saccharification and fermentation . . . . . . . . . . . . . . . . . . . . . 150 6. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 Acknowledgement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 1. Introduction Lactic acid (2-hydroxypropionic acid or 2-hydroxypropanoic acid), CH 3 -CHOHCOOH, is the most widely occurring carboxylic acid, having a prime position due to its versatile applications in food, pharmaceutical, textile, leather, and other chemical industries (Vickroy 1985; Wee et al., 2006; John et al., 2007). Lactic acid is widely used in the food related applications but recently it has gained many other industrial applica- tions like biodegradable plastic production. Food and food-related applications account for approximately 85% of the demand for lactic acid, whereas the nonfood industrial applications account for only 15% of the demand. Lactic acid has been used as a preservative and acidulant in food and beverage sector for several decades. Calcium lactate is a good dough conditioner, whereas sodium lactate acts both as conditioner and as emulsifier. Lactic acid is considered as generally recognized as safe (GRAS) for use as food additives by the regulatory agencies like FDA in USA. It is used as acidulant, flavoring or buffering agent or inhibitor of bacterial spoilage in a wide variety of processed foods, such as candy, Biotechnology Advances 27 (2009) 145–152 ⁎ Corresponding author. Tel.: +91 471 2515339; fax: +91 471 2491712. E-mail address: rojanpj@yahoo.co.in (R.P. John). 0734-9750/$ – see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.biotechadv.2008.10.004 Contents lists available at ScienceDirect Biotechnology Advances journal homepage: www.elsevier.com/locate/biotechadv