Abstract: Solutions containing nucleic acids are treated with an alkaline protease to digest proteins such as nucleases that degrade the nucleic acids. In the isolation of nucleic acids, a biological sample containing nucleic acids is suspended in a solution containing water, buffer and chelating agent, the pH of the solution is adjusted to at least about 10 by adding a solution of sodium hydroxide and anionic detergent, an alkaline protease is incubated in the solution until nucleases are degraded, the pH of the solution is lowered to reduce activity of the alkaline protease by adding a solution having a pH between 3.5 and 4.5 and the alkaline protease is heat inactivated. Lowering of the pH may produce a cloudy solution which is cleared by centrifuging. Nucleic acids are isolated from the cleared solution by alcohol precipitation, or by using paramagnetic particles or a resin matrix containing silica particles. A chaotropic salt can be used to reversibly bind DNA to the resin matrix.

Abstract: Proteases are susceptible to autolytic degradation. The method of the invention provides a method to identify susceptible autolysis sites which are cleaved to produce a few discrete fragments. Once identified, amino acid(s) at or in the vicinity of the cleavage site may be chemically modified or the DNA sequence capable of encoding the amino acid present at the site may be changed or deleted by site directed mutagenesis to produce an autolysis stable protease. The invention is particularly applicable to alkaline proteases which are produced in large quantities and used as detergent additives. Stable alkaline proteases could then be used in liquid detergent formulations.

Abstract: A method is provided for detecting a microorganism which produces a desired substance. The method involves overlaying a membrane on an agar surface in a predetermined orientation. Microorganisms are grown on the membrane and the substance allowed to pass into the agar. The membrane is removed and a detectable reaction between the substance and one or more reagents is observed. The location of the microorganism to be detected can be determined by the predetermined orientation, and the microorganism can be isolated by removing it from the membrane. When the substance is not secreted by the microorganism, the microorganisms are lysed releasing the substance for passage into the agar. The microorganisms producing the substance can be located on replicate plates and isolated.