Biologia

Bioresource Technology 102 (2011) 6344–6347

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Bioresource Technology
journal homepage: www.elsevier.com/locate/biortech

Short Communication

Effect of enzyme producing microorganisms on the biomass of epigeic earthworms (eisenia fetida) in vermicompost
Sung Wook Hong, Ju Sam Lee, Kun Sub Chung ⇑
Division of Biological Science and Technology,Yonsei University, Republic of Korea

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We analyzed the bacterial community structure of the intestines of earthworms and determined the effect of enzyme producing microorganisms on the biomass of earthworms in vermicompost. Fifty-seven bacterial 16S rDNA clones were identified in the intestines of earthworms by using polymerase chain reaction-denaturinggradient gel electrophoresis (PCR-DGGE) analysis. Entomoplasma somnilux and Bacillus licheniformis were the dominant microorganisms; other strains included Aeromonas, Bacillus, Clostridium, Ferrimonas, and uncultured bacteria. Among these strains, Photobacterium ganghwense, Aeromonas hydrophila, and Paenibacillus motobuensis were enzyme-producing microorganisms. In the mixtures that wereinoculated with pure cultures of A. hydrophila WA40 and P. motobuensis WN9, the highest survival rate was 100% and the average number of earthworms, young earthworms, and cocoons were 10, 4.00– 4.33, and 3.00–3.33, respectively. In addition, P. motobuensis WN9 increased the growth of earthworms and production of casts in the vermicompost. These results show that earthworms and microorganisms have asymbiotic relationship. Ó 2011 Elsevier Ltd. All rights reserved.

Article history: Received 17 December 2010 Received in revised form 11 February 2011 Accepted 23 February 2011 Available online 21 March 2011 Keywords: Earthworm Biomass Vermicompost Denaturing gradient gel electrophoresis

1. Introduction Vermicomposting is a waste management technique that promotes the conversion of organic wasteinto organic fertilizers (Garg et al., 2006). Earthworms are usually used for vermicomposting because they possess higher composting activity (Tripathi and Bhardwaj, 2004). Vermicomposting is a mesophilic process, which uses microorganisms and earthworms. In addition, it is faster and produces a richer end product than composting. Because organic material passes through the earthworm gut, theresulting vermicast (earthworm manure) is abundant in microbial activity, plant growth regulators, and pest repellants. The epigeic earthworm, Eisenia fetida, commonly known as a red wiggler, is a particularly efficient vermicomposting earthworm because it can consume its own body weight in food each day (Tripathi and Bhardwaj, 2004). In E. fetida, a variety of intestinal microorganisms that produceenzymes, such as amylase, proteases, lipases, and cellulases, enhance the biodegradation of organic matter (Aira et al., 2005). Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) is a molecular fingerprinting technique that is based on differences in the melting behavior of PCR amplified fragments in denaturing gradient gels (Muyzer et al., 1993). As a result, PCR-

DGGE canbe used to differentiate bacteria on the basis of sequence differences in their 16S rDNA. To better understand the beneficial effects of earthworms on soil properties, the role of intestinal microorganisms in earthworms needs to be defined. Although it is known that the intestines of earthworms host a variety of soil microorganisms (Parle, 1963), little is known about their interactions. In thisstudy, we used PCR-DGGE to investigate the symbiotic relationship between earthworms and microorganisms. Specifically, we analyzed the growth and reproduction of earthworms in vermicompost that was inoculated with enzyme producing microorganisms. 2. Methods 2.1. Sample preparation and enzyme assay Adult E. fetida were collected from an earthworm farm in Eumsung, Korea. The surface of the earthworms...