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 10(3)-10(6) cfu g-1 d.w., whereas the untreated pulps contained 10(8)-10(10) cfu g-1 d.w. Aerobic, anaerobic and facultatively anaerobic spore-forming bacteria formed a large group in the bacterial flora of pulp samples (10(3)-10(6) and 10(2)-10(4) cfu g-1 d.w., respectively). In the boards the maximum numbers of aerobic spore-forming bacteria were about 10(4) cfu g-1 d.w. and the numbers of anaerobic and facultatively anaerobic spore formers were negligible. Moulds were common in the untreated pulp sampled at 10(2)-10(6) 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 circulation process water. Both mesophilic and thermophilic actinomycetes were detected in pulps at levels up to 10(2)-10(5) cfu g-1 d.w. However, no mesophilic actinomycetes were detected in boards, although some boards contained up to 10(2) 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.