Microbiological examination of air-borne and resident microflora in a kenkey production plant and a mushroom production centre

Abstract

The microbial load of lactic acid bacteria, aerobic mesophiles, yeasts and moulds on the surfaces of a steeping tank and fermentation trough in an upgraded fermented maize dough and kenkey production plant and on a laboratory floor and bench top in a mushroom spawn producing laboratory were enumerated on Universal Beer Agar, Plate Count Agar, Malt Agar and DO 18. The air-borne microflora in these two facilities were also investigated. The microflora of the kenkey production plant contained 1OS-106cfulml and 104-1OS cfulml. lactic acid bacteria in the fermentation trough and the steeping tank respectively. Lactobacillus species were found to be the dominant species accounting for 89-90% of all organisms isolated on Universal Bear Agar. The other major lactic acid bacteria identified was Pediococcus species accounting for 10-11%. The microflora on Plate Count Agar in both the trough and the tank were at levels of 105cfulml with Bacillus species forming the dominant flora accounting for 80.2% and 43.2% from the fermenting trough and steeping tank respectively. Cocci isolated were identified as Staphylococcus/micrococcus species forming 13.2% in the fermentation trough and 28.4% in the steeping tank. The microbial population on Plate Count Agar also contained 6.6% and 21.3% yeasts from the fermenting trough and steeping tank respectively which were identified as mainly Saccharomyces cerevisiae. The yeasts population enumerated on Malt extract Agar containing chloramphenicol and chlotetracycline was dominanted by Candida krusei. The flora of air sample from the kenkey production plant was dominated by Bacillus species accounting for 67% of all isolates examined on PCA. Moulds were isolated from the air sample the dominant genus being Aspergillus spp., Fusarium spp. and Mucor spp. The microbial load at the National Mushroom Development Project were found to be 102 _103cfulml. on PCA and 102 cfulml on DO 18 plates from both laboratory floor and a laboratory bench top. The counts of microorganisms in the air of the laboratory were 19-25 cfulmin. on PCA and 4-7 cfulrnin. on DO 18 plates. Staphylococcus and Micrococcus species accounted for 68.7%, 40% and 8.3% of the population of aerobic mesophiles of laboratory floor, laboratory bench top and laboratory air sample enumerated on Plate Count Agar whilst Bacillus species accounted for 18.8%, 50% and 75.1% of the population respectively. Yeasts isolated were identified as Sacch. cerevisiae. The moulds Aspergillus and Penicilium spp were isolated from air sample whilst Aspergillus niger was isolated from laboratory bench top. The laboratory floor was. however, colonised by Aspergillus spp, Penicillium spp ,Fusarium species and Paecilomyces variotii