Manganese was accumulated by cells of Escherichia coli by means of an active transport system quite independent of the magnesium transport system. When the radioisotope 54 Mn was used, manganese transport showed saturation kinetics with a K m of 2 × 10 −7 m and a V max of 1 to 4 nmoles/min per 10 12 cells at 25 C. The manganese transport system is highly specific; magnesium and calcium did not stimulate, inhibit, or compete with manganese for cellular uptake. Cobalt and iron specifically interfered with 54 Mn uptake, but only when added at concentrations 100 times higher than the K m for manganese. Active transport of manganese is temperature- and energy-dependent: uptake of 54 Mn was inhibited by cyanide, dinitrophenol, and m -chlorophenyl carbonylcyanide hydrazone (CCCP). Furthermore, the turnover or exit of manganese from intact cells was inhibited by energy poisons such as dinitrophenol and CCCP.

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Pectinesterase was isolated from Bramley apple waste (peel, cores and offcuts)

The in situ de-esterification of pectin in lime pulp by the action of pectinesterase (PE) has been investigated. It has been shown that the degree of pectin esterification is reduced to about 20% when the pulp is held at pH 8.5 for 90 min. The rate of de-esterification by the enzyme in situ is highest when the pH is in the range 7.5-9.0 and the NaCl concentration is 0.1-0.3111. At pH values above 9 chemical de-esterification becomes important. The activity of extracted lime PE was shown to be almost independent of pH in the range pH 6.c9.0. It is suggested that the difference between the behaviour of the extracted and the in situ enzyme is due to the fact that the latter needs to be solubilised before it can act on some of the pectin in the pulp. In support of this it is found that the proportion of lime PE which can be extracted from the pulp decreases with decreasing pH and ionic strength, reflecting electrostatic binding to the cell wall.