ORIGINAL PAPER Lipase production by Aspergillus ibericus using olive mill wastewater Luı ´s Abrunhosa • Felisbela Oliveira • Danielle Dantas • Cristiana Gonc ¸alves • Isabel Belo Received: 11 May 2012 / Accepted: 28 June 2012 / Published online: 13 July 2012 Ó Springer-Verlag 2012 Abstract Olive mill wastewater (OMW) characteristics make it a suitable resource to be used as a microbial culture media to produce value-added compounds, such as enzymes. In this work, the ability of the novel species Aspergillus ibericus to discolor OMW and produce lipase was studied. An initial screening on plates containing an OMW-based agar medium and an emulsified olive oil/ rhodamine-B agar medium was employed to select the strain A. ibericus MUM 03.49. Then, experiments in con- ical flasks with liquid OMW-based media showed that the fungus could growth on undiluted OMW, with a chemical oxygen demand (COD) of 97 ± 2 g/L, and to produce up to 2,927 ± 54 U/L of lipase. When pure OMW was used in the media, the maximum COD and color reduction achieved were 45 and 97 %, respectively. When OMW diluted to 10 % was used, A. ibericus was able to reduce phenolic and aromatic compounds by 37 and 39 %, respectively. Additionally, lipase production was found to be promoted by the addition of mineral nutrients. When the fermentations were scaled up to a 2-L bioreactor, A. ibe- ricus produced up to 8,319 ± 33 U/L of lipase, and the maximum COD and color reduction were 57 and 24 %, respectively. Keywords Olive mill wastewater Á Aspergillus ibericus Á Lipase Á Chemical oxygen demand Á Submerged fermentation Introduction Olive oil is a traditional agricultural product that is origi- nally from the Mediterranean basin; the majority (approx. 75 %) of the world’s olive oil comes from southern Euro- pean countries [1, 2]. According to the 2010 FAO data, the 10 most relevant producers of olive oil are Spain (with an annual production of 1.5 9 10 6 tons), Italy, Greece, Syria, Tunisia, Turkey, Morocco, Algeria, Portugal and Argentina [1]. In Portugal, approximately 71,800 tons of olive oil was produced in 2011/2012 campaign, which represents approximately 2 % of the world’s production [2]. Olive oil is extracted from olives by physical methods. Olive crushing, malaxation of the resulting paste and oil phase separation are the most important stages of the extraction process. Currently, these steps are performed by three different methods: (i) the traditional discontinuous pressing process that is still used in many small olive mills, (ii) the continuous process with three-phase horizontal cen- trifuge systems that separate the olive pulp into oil, liquid waste and solid residue, and (iii) the continuous process with two-phase horizontal centrifuge systems that separate the olive pulp into oil and wet solid residue [3]. The first two processes require the addition of hot water, producing large amounts of liquid waste known as olive mill wastewater (OMW), which is a significant source of agro-industrial pollutants [4]. OMW characteristics are variable and depend on the properties of the olives processed and the kind of extraction method used. The discontinuous process produces a lower amount of more concentrated OMW, while the three- phase system generates approximately twice the volume of less-concentrated OMW. Typical volumes produced range from 0.4 to 1.2 m 3 per ton of olives processed [3]. In general, OMW has a dark brown color, is acidic and has a high content of organic matter. The main compounds found in OMW are L. Abrunhosa Á F. Oliveira Á D. Dantas Á C. Gonc ¸alves Á I. Belo (&) Institute for Biotechnology and Bioengineering (IBB), Centre of Biological Engineering, University of Minho, Campus de Gualtar, 4710-057 Braga, Portugal e-mail: ibelo@deb.uminho.pt 123 Bioprocess Biosyst Eng (2013) 36:285–291 DOI 10.1007/s00449-012-0783-4