Biodegradation of the fungicide carbendazim by bacteria from Coriandrum sativum L. rhizosphere/ Biodegradacao do agrotoxico carbendazim por bacterias da rizosfera de Coriandrum sativum L

The biocidal agrochemicals commonly used in agriculture can remain in the soil, affecting the environmental conditions and causing serious risks to health. Knowing that soil microorganisms, especially those from the rhizosphere, can degrade environmental xenobiotics, it was evaluated the potential of bacteria isolated from Coriandrum sativum L. rhizosphere to biodegrade carbendazim (MBC), a fungicide extensively used by agriculturists from rural farming communities in Manaus, Amazonas. Cultures carried out in medium containing carbendazim as a sole carbon source enabled the isolation of 80 bacteria, in the established conditions. Assays to determine degradation potential allowed the selection of the two elite isolates identified as Stenotrophomonas sp. and Ochrobactrum sp. Quantitative assays with each strain individually or in consortium, were carried out using minimal salt medium added with carbendazim (250 [micro]g [mL.sup.-1]) and incubated at 30[degrees]C, under agitation (125 rpm) for 21 days. Samples used in the biodegradation test were HPLC analyzed for final fungicide quantitation. The Stenotrophomonas sp. strain was more efficient (68.9%) to degrade carbendazim and showed no toxicity in tests with Artemia salina. Keywords: Amazon soil, fungicide, coriander, carbendazim-degrading bacteria, Stenotrophomonas, xenobiotics. Agrotoxicos sao comumente utilizados na producao agricola, podendo persistir no solo, afetar a qualidade do ambiente e causar serios riscos a saude. Sabendo-se que micro-organismos do solo, principalmente aqueles da rizosfera, podem degradar produtos xenobioticos avaliou-se o potencial de bacterias isoladas da rizosfera de Coriandrum sativum L. em degradar carbendazim, um fungicida usado extensivamente em comunidades de agricultores rurais em Manaus, Amazonas. Procedimentos de cultivo em meio, contendo carbendazim como unica fonte de carbono, mostraram que 80 bacterias cresceram nas condigoes estabelecidas. Ensaios de eficiencia de degradacao permitiram a selecao dos dois melhores isolados que foram identificados como Stenotrophomonas sp. e Ochrobactrum sp. Os ensaios quantitativos, com cada cepa individualmente e com as duas em consorcio, foram conduzidos em meio minimo contendo sais, acrescido de carbendazim (250 [micro]g [mL.sup.-1]) e incubados a 30[degrees]C, 125 rpm, por 21 dias. A quantificacao final do fungicida nas amostras do ensaio de biodegradacao foi realizada em HPLC. A linhagem Stenotrophomonas sp. apresentou maior e