PubMed · 6741775
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L Greenberg. 1984. Program on heat stress computation.. https://pubmed.ncbi.nlm.nih.gov/6741775/
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Heat resistance of Talaromyces flavus was determined using two methods. Standard thermal death time vials were used to determine the heat resistance of T. flavus ascospores, from 80 to 90 degrees C with a decimal reduction time D90 of 6.2 min. A continuous two-phase slug flow heat exchanger system with heating, holding and cooling sections was used to determine the heat resistance from 90 to 100 degrees C. Inoculated heating medium was pumped through 1.85 mm ID tubing in 'slugs' separated by air bubbles to interrupt laminar flow. Varying pump speed, length of tubing in the heating bath and temperature allowed collection of data under varied heating conditions. D90 with the slug flow heat exchanger system was 6.4 min, indicating the two methods were comparable, z values were 6.7 and 6.4 degrees C, respectively. The slug flow heat exchanger system permits rapid determination of heat resistance over a range of temperatures. Because of minimum come-up time the slug flow heat exchanger can be used at temperatures near the upper limit of heat resistance for the microorganism being tested.
Z (Glu342 --> Lys) and S(iiyama) (Ser53 --> Phe) genetic variations of human alpha1-antitrypsin (alpha1-AT) cause a secretion blockage in the hepatocytes, leading to alpha1-AT deficiency in the plasma. Using in vitro folding analysis, we have shown previously that these mutations interfere with the proper folding of polypeptides. To understand the fundamental cause for the secretion defect of the Z and S(iiyama) variants of alpha1-AT, we investigated in vivo folding and stability of these variant alpha1-AT using the secretion system of yeast Saccharomyces cerevisiae. Various thermostable mutations suppressing the folding block of the Z variant in vitro corrected the secretion defect as well as the intracellular degradation in the yeast secretion system. Significantly, the extent of suppression in the secretion defect of Z protein was proportional to the extent of suppression in the folding defect, assuring that the in vivo defect associated with the Z variant is primarily derived from the folding block. In contrast, the folding and secretion efficiency of S(iiyama) was not much improved by the same mutations. In addition, none of the rarely secreted S(iiyama) alpha1-AT carrying the stabilizing mutations for the wild type and Z variant were active. It appears that the major defect in S(iiyama) variant is the loss of stability in contrast to the kinetic block of folding in the Z variant.
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