Bacterial community diversity in paper mills processing recycled paper

Paper mills processing recycled paper suffer from biofouling causing problems both in the mill and final product. The total bacterial community composition and identification of specific taxa in the process water and biofilms at the stock preparation and paper machine areas in a mill with recycled paper pulp was described by using a DNA-based approach. Process water in a similar mill was also analyzed to investigate if general trends can be found between mills and over time. Bacterial community profiles, analyzed by terminal-restriction fragment length polymorphism (T-RFLP), in process water showed that the dominant peaks in the profiles were similar between the two mills, although the overall composition was unique for each mill. When comparing process water and biofilm at different locations within one of the mills, we observed a separation according to location and sample type, with the biofilm from the paper machine being most different. 16S rRNA gene clone libraries were generated and 404 clones were screened by RFLP analysis. Grouping of RFLP patterns confirmed that the biofilm from the paper machine was most different. A total of 99 clones representing all RFLP patterns were analyzed, resulting in sequences recovered from nine bacterial phyla, including two candidate phyla. Bacteroidetes represented 45% and Actinobacteria 23% of all the clones. Sequences with similarity to organisms implicated in biofouling, like Chryseobacterium spp. and Brevundimonas spp., were recovered from all samples even though the mill had no process problems during sampling, suggesting that they are part of the natural paper mill community. Moreover, many sequences showed little homology to as yet uncultivated bacteria implying that paper mills are interesting for isolation of new organisms, as well as for bioprospecting.     

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Description of heterotrophic bacteria occurring in paper mills and paper products

AIMS: To isolate aerobic mesophilic bacilli and thermophilic bacteria from different paper mill samples and to evaluate their potential harmfulness. METHODS AND RESULTS: A total of 109 mesophilic and 68 thermophilic isolates were purified and characterized by automated ribotyping and partial 16S rDNA sequencing. The mesophilic isolates belonged to the genera Bacillus (13 taxa), Brevibacillus (three taxa) and Paenibacillus (five taxa). The thermophilic bacteria represented seven taxa of Bacillus, Geobacillus or Paenibacillus, four of proteobacteria and one of actinobacteria. The most frequently occurring bacteria were Bacillus cereus, B. licheniformis, Pseudoxanthomonas taiwanensis and bacteria closely related to Paenibacillus stellifer, P. turicensis or Leptothrix sp. One mill was contaminated throughout with bacteria of a novel mesophilic genus most closely related to Brevibacillus centrosporus and another with bacteria of a novel thermophilic genus most closely related to Hydrogenophilus thermoluteolus. One B. cereus isolate producing haemolytic diarrhoeal enterotoxin was detected and all the tested B. licheniformis isolates produced a metabolite toxic to boar sperm cells. CONCLUSIONS: The bacilli and thermophilic bacteria isolated represent species which should not present occupational hazards in paper mill environments. The most harmful bacterium detected was B. licheniformis and potentially also B. cereus. SIGNIFICANCE AND IMPACT OF THE STUDY: Knowledge of the microbial diversity in a paper mill provides a rational basis for development of an effective controlling programme. A database constructed from the fingerprints generated using automated ribotyping helps to identify and trace the contamination routes of bacteria occurring in paper mills.