Aims: The present study describes a flow cytometric technique for quantification and differentiation of bacteria in bulk tank milk according to the main cause of elevated counts. Methods and Results: A total of 75 Danish bulk tank milk samples exceeding the grading level of 3AE0 · 10 4 CFU ml )1 were examined by both flow cytometry and traditional microbiological analyses. The correlation coefficient (r) between the two methods was 0AE71. For the differential analyses of the dominant bacterial populations four different parameters were used to give a species-characteristic pattern. The four parameters were as follows: staining with Oregon Green Ò conjugated wheat germ agglutinin that binds to the cell wall of bacteria, staining with hexidium iodide that binds to all bacterial DNA, the flow cytometric forward scatter and the flow cytometric side scatter. Three regions in the flow cytometric plot were defined: region 1 includes bacteria mainly associated with poor hygiene, region 2 includes psychrotrophic hygiene bacteria and region 3 includes bacteria mainly related to mastitis. The ability of the flow cytometric technique to predict the main cause of elevated bacterial counts on routine samples was examined. Comparing these results with results obtained by traditional microbiological analyses for identification showed that for 81% of the samples the two techniques agreed on the main cause of an elevated bacterial count.
Conclusions:The ability of the presented flow cytometric technique to enumerate and differentiate bacteria in bulk tank milk according to the main cause of elevated counts was demonstrated. Significance and Impact of the Study: This study described the first step in development of a technique suitable for routine analyses of bulk tank milk samples. A technique indicating the main cause of an elevated count will enable the farmer to eliminate the contamination source within a short time limit.
Escherichia coli was grown as a continuous culture at various defined conditions of temperature, pH, aeration rate and dilution rate. The lipids were extracted from disrupted cells and the relative fatty acid content of the individual and total phospholipids was determined. The lipid composition of E. coli was shown to change with the fermentation conditions. Interestingly, E. coli adapted to high growth rates and to low oxygen tension by changing the lipid composition of the membrane in exactly the same way, thus indicating a common effect.
The acetolactate decarboxylase produced by Lactobacillus casei DSM 2547 has been tested as an aid for accelerated removal of the diacetyl precursor acetolactic acid from beer. Addition of the enzyme to freshly fermented beer has been shown to effect efficient removal of the diacetyl precursor while addition of the decarboxylase to wort prior to pitching was found to lead to subsequent inactivation of the enzyme during the fermentation. It has been shown that zinc is a component of the acetolactate decarboxylase system, and that growing yeast cells remove the zinc ions.
Eleven different strains of Penicillium were screened for production of mannitol. All strains produced both mannitol and glycerol. Some of the strains also produced arabitol and/or erythritol in lower amounts. The highest amount of mannitol (43 g dm−3) was produced by Pencillium scabrosum IBT JTER 4, and the highest combined yield of mannitol and glycerol (65 g dm−3) was obtained with Pencillium aethiopicumIBT MILA 4 when grown on 150 g dm−3 sucrose and 20 g dm−3 yeast extract. These yields are comparable to yields obtained with Aspergillus strains after a considerable optimization effort. It is thus likely that biotechnological production of mannitol may benefit from the development of suitable Penicillium strains.
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