Biotechnology Letters 24: 287–291, 2002.© 2002 Kluwer Academic Publishers. Printed in the Netherlands.287Microbial degradation of acetonitrile using a suspended-carrier biofilmprocessKristina Håkansson∗& Bo MattiassonDepartment of Biotechnology, Center for Chemistry and Chemical Engineering, Lund University P.O. Box 124,SE-221 00 Lund, Sweden∗Author for correspondence (Fax: +46 46 222 47 13; E-mail: kristina.hakansson@biotek.lu.se)Received 31 October 2001; Revisions requested 7 November 2001; Revisions received 10 December 2001; Accepted 14 December 2001Key words: acetonitrile, activated sludge, biofilm, destruction, microbial processAbstractA microbial process for the destruction of acetonitrile has been developed.Suitable microorganismswere enrichedfrom activated sludge by cultivation with a high selection pressure when acetonitrile was the sole source of carbonand nitrogen. The process is based on cultivating the microorganisms as a biofilm on plastic carriers. These areutilisedina stirred-tankreactorwithcontinuousfeedingof40–150mMacetonitrileandanoutletforspentmedium.The observed efficiency in the conversion process was from 53–100%, depending on the organic load. To improvethe capacity and reliability of the process, a two-step process was developedwith two stirred-tank reactors coupledin series. With such an arrangement, conversion efficiencies from 92–100% were achieved when the organic loadwas 2 g acetonitrile l−1d−1in the first reactor.IntroductionEnormous amounts of waste chemicals are produced.Many of them are highly toxic and their destructionconstitutes a major problem. In Sweden, they are col-lected and transported to a central incineration plant.Such a routine means that hazardous chemicals arehandled and transported across the country just for thesake of destruction. If a de-centralised destruction al-ternative was available, it would be possible to reducethe handling of toxic chemicals substantially.Examples of chemicals that could be treated lo-cally, and which represent a large fraction of the totalvolume,includeorganicsolvents.Inthestudyreportedhere, the focus is on degradation of acetonitrile. Thisis a volatile, toxic and highly polar solvent used forthe preparation of a variety of compounds like phar-maceuticals, perfumes, etc. It is also used as elutingmedium in HPLC, and thus large volumes are handledannually (WHO 1993, Ramakrishna et al. 1999).Acetonitrile can be degraded microbially (Nawazet al. 1989, 1991, Chapatwala et al. 1993a,b, 1995,Babu & Chetty 1994, Ramakrishna et al. 1999).Degradationof aliphatic nitriles like acetonitrile, acry-lonitrile etc. occurs in two steps (Thompson et al.1988):The present investigation was focused on obtaining anefficient acetonitrile-degrading culture using high celldensity reactors.
