A study of the microflora of some recycled fibre pulps, boards and kitchen rolls

Current methodology used for studying the microflora of pulps and boards was assessed and some improvements are recommended. Microbiological quality of 37 samples including recycled fibre pulps, boards, kitchen rolls, virgin fibre sheets and circulating process water were investigated. The papermaking process had drastically reduced the total microbial counts. The dominant microflora in all the samples were aerobic bacteria. The amounts in boards were only 103–106 cfu g−1 d.w., whereas the untreated pulps contained 108–1010 cfu g−1 d.w. Aerobic, anaerobic and facultatively anaerobic spore‐forming bacteria formed a large group in the bacterial flora of pulp samples (103–106 and 102–104 cfu g−1 d.w., respectively). In the boards the maximum numbers of aerobic spore‐forming bacteria were about 104 cfu g−1 d.w. and the numbers of anaerobic and facultatively anaerobic spore formers were negligible. Moulds were common in the untreated pulp samples at 102–106 cfu g−1 d.w., but their occurrence in boards was close to the detection limit. Yeasts were common only in the pulps of one mill, and were found to be present in the circulating process water. Both mesophilic and thermophilic actinomycetes were detected in pulps at levels up to 102–105 cfu g 1 d.w. However, no mesophilic actinomycetes were detected in boards, although some boards contained up to 102 cfu g−1 d.w. of thermophilic actinomycetes. The virgin fibre sheets were practically free of microbes. Only a few bacterial colonies were detected from the kitchen rolls.