In view of the disuse of agricultural lands in Europe and other parts of the world, there is an ever-increasing de- mand for options for alternative uses for agricultural prod- ucts in the non-food sector. Renewable raw materials can be utilized directly, e.g., as energy carriers, as packaging materials, as fibers, for the production of coloring agents or as lubricants. However, they can also be converted biotechnologically by enzymes and microorganisms, giv- ing us access to a multitude of new, biocompatible prod- ucts and possible uses [1]. Often the economy of bio- processes is still the problem because, in the case of bulk products, the price is affected mainly by raw material costs [2]. Biotechnological production of lactic acid as an example of these “building blocks” is carried out in tech- nical reactors using a suitable bacterial strain. Lactic acid, its salts and esters have a wide range of potential uses and are extensively used in diverse fields of food, in- dustrial, cosmetic, pharmaceutical industries and agri- culture [3, 4]. Lactic acid formation and cell growth are closely coupled in lactic acid fermentation. An overview of the utilization of different renewable resources for lac- tic acid fermentation, other microorganisms and yields depending on several process parameters is given in [5]. The goal is to develop a fermentation process based on the substitution of expensive nutrient supplements by cheaper materials from renewable resources, as these supplements represent a major part of the whole produc- tion costs [6]. Depending on the further processing of the lactic acid (e.g., for bioplastics), the separation of impuri- ties after fermentation can also represent a major process cost [7]. Therefore, an optimization is necessary to find a balance between the substitution of expensive nutrients and the limitation of interfering or undesirable compo- nents of natural raw materials. Technical Report Utilization of renewables for lactic acid fermentation Joachim Venus Department of Bioengineering, Leibniz-Institute for Agricultural Engineering Potsdam-Bornim e.V., Potsdam, Germany Originally, lactic acid was produced from pure substrates like glucose. Increasingly, however, agri- cultural feedstocks such as grains and green biomass are also being used as raw materials for the biotechnological production of lactic acid. A high-productivity lactic acid bacterium strain was se- lected, process parameters were optimized for the batch fermentation on a laboratory scale, and its performance at cultivation on a barley hydrolysate medium together with different supplements was examined. The present results for the cultivation of the Lactobacillus paracasei on complex nutrient broth are in the same range as those for another strain of the same species with pure glu- cose, de Man, Rogosa and Sharpe medium (MRS) minerals, peptone and yeast extract. Under these conditions, this strain was able to accumulate more than 100 g lactate/L in the MRS medium. Medium optimization experiments showed that the main part of the nitrogen-contain- ing nutrients in the medium (peptone, yeast extract) can be replaced by protein extracts from green biomass (lucerne green juice). The green juice after pressing fresh biomass contains a series of nitrogen-containing compounds and inorganic salts, which are essential for cell growth. Thus, on laboratory scale, we have demonstrated that it is possible to substitute synthetic nutrients by re- newable resources like cereals and green biomass without any loss of productivity. This high bio- mass concentration together with the number of living cells, could increase the productivity to higher levels compared to the well-adapted synthetic nutrients of MRS. Keywords: Bioconversion · Lactic acid · Renewable resources Correspondence: Dr. Joachim Venus, Department of Bioengineering, Leib- niz-Institute for Agricultural Engineering Potsdam-Bornim e.V., Max-Eyth- Allee 100, 14469 Potsdam, Germany E-mail: jvenus@atb-potsdam.de Fax: +49-331-5699-849 Abbreviations: DM, dry matter; MRS, de Man, Rogosa and Sharpe medium Received 13 September 2006 Revised 19 October 2006 Accepted 31 October 2006 Biotechnology Journal DOI 10.1002/biot.200600180 Biotechnol. J. 2006, 1, 1428–1432 1428 © 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim