SummaryCulture filtrates from three mutant strains of Trichoderma reesei grown on lactose and on cellulose were compared under use conditions on four cellulose substrates. Cellulose culture filtrates contained five to six times as much cellulase as lactose culture filtrates. Unconcentrated cellulose culture filtrates produced up to 10% sugar solutions from 1570 cellulose in 24 h. Specific activity in enzyme assays and efficiency in saccharification tests were low for enzymes from all the mutants. Over a wide range the percent saccharification of a substrate in a given time was directly proportional to the logarithm of the ratio of initial concentrations of enzyme and substrate. As a result of this, dilute enzyme is more efficient than concentrated enzyme, but if high sugar concentrations are desired, very large quantities of enzyme are required. Since the slopes of these plots varied, the relative activity of cellulase on different substrates may be affected by enzyme concentration.

Glucosidase of Aspergillus phoenicis QM 329 was immobilized on chitosan, using the bifunctional agent glutaraldehyde. The most active preparation based on the amount of support contained a 1:2.5 enzyme-to-chitosan ratio (wt/wt). However, the specific activity of the bound enzyme decreased from 10 to 1% with increasing enzyme-to-chitosan ratio. Compared with free f-glucosidase, the immobilized enzyme exhibited: (i) a similar pH optimum but more activity at lower pH values; (ii) improved thermal stability; (iii) a similar response to inhibition by glucose; and (iv) mass transfer limitations as reflected by higher apparent Km and lower energy of activation.

The presence of four thioureas in a mixture derived from the volatile isothiocyanates of fresh white cabbage has been indicated by paper chromatography and countercurrent distribution. The predominant component has been proved unequivocally to be allylthiourea by isolation of S-methyl-S-allylisothiuronium picrate, and the presence of 3-methylthiopropylthiourea has been established unambiguously by chromatography and infrared spectroscopy. Evidence is presented that two of the remaining constituents are 3-butenylthiourea and 3-methylsulfinylpropylthiourea. Estimates of the quantities of isothiocyanates present in fresh cabbage are gi\ en.The nature of the isothiocyanates in various plants of the genus Brassica has been the subject of several recent investigations. 2 , 3 With few exceptions, the seeds, rather than the fresh parts of the plant, have been studied. The volatile isothiocyanates released from the thioglucosides in cabbage are believed to be of importance to the taste and odor of the fresh ~e g e t a b l e .~ The presence of allyl isothiocyanate in the head of white cabbage and of allyl isothiocyanate and 3-butenyl isothiocyanate in the head of red cabbage has been indicated, on the basis of paper chromatographic evidence in only one solvent system, by Kjaer and co-workers. 2a In the present investigation, the fresh, wet tissues of white cabbage heads were macerated, subjected to enzymatic action for the liberation of the mustard oils from the thioglucosides, and extracted with n-hexane. The resultant solution of isothiocyanates was steam distilled and converted to thioureas. Paper chro>natography indicated the presence of four thioureas, namely, allyl-, 3-methylthiopropyl-, 3-butenyl-and 3-methylsulfinylpropy1-thiourea5 The simultaneous occurrence of allyl and 3-methylthiopropyl isothiocyanates is reasonable since the former (or its glucoside) could be derived from the latter by the mere loss of methyl mercaptan.Allylthiourea was separated from the mixture by countercurrent distribution. I t was characterized by the formation of a crystalline derivative, S-methyl-N-allylisothiuronium picrate. The identity of the derivative with an authentic sample6 was established by a mixed melting point determination, X-ray diffraction analysis and infrared spectra of the natural and synthetic compounds, giving the first unequivocal proof of the occurrence of allyl isothiocyanate in fresh cabbage leaves.

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