System for Environmental Microbial Testing

Abstract

A gelled biological growth medium in a culture container, as well as kits and methods of producing the growth medium, utilize gelling of a liquid growth medium containing low methoxyl pectin on a film of calcium salt deposited on a growth surface of the culture container. The salt acts as a trigger for gelation and is conveniently deposited on the walls by evaporation of methanol or another volatile solvent.

What is claimed is: 
     
         1 . A kit for preparing a gelled growth medium, the kit comprising:
 a) a liquid growth medium comprising a low methoxyl pectin material having less than about 8% methoxyl content; and   b) a container for culturing microorganisms, wherein the container comprises a calcium lactate precipitate on a growth surface of the container.   
     
     
         2 . The kit of  claim 1 , further comprising:
 c) instructions for coating the calcium lactate precipitate with a liquid growth medium to form a gelled biological growth medium.   
     
     
         3 . The kit of  claim 1 , wherein the liquid growth medium is selected from the group consisting of potato dextrose broth, yeast extract dextrose broth, and combinations thereof. 
     
     
         4 . The kit of  claim 1 , wherein the liquid growth medium further comprises an antibacterial agent. 
     
     
         5 . The kit of  claim 4 , wherein the liquid growth medium comprises from about 50 to about 100 micrograms per milliliter of chloramphenicol as the antibacterial agent. 
     
     
         6 . The kit of  claim 1 , wherein the container is a Petri dish. 
     
     
         7 . The kit of  claim 1 , wherein the container for culturing microorganisms comprises from about 50 to about 350 mg of calcium lactate per gram of low methoxyl pectin in the liquid growth medium. 
     
     
         8 . The kit of  claim 1 , which is suitable for preparing a gelled growth medium for selective growth of yeast or mold. 
     
     
         9 . A kit for preparing a gelled growth medium, the kit comprising:
 a) a liquid growth medium comprising a low methoxyl pectin material having less than about 8% methoxyl content;   b) a solution comprising calcium lactate and methanol; and   c) a container for culturing microorganisms.   
     
     
         10 . The kit of  claim 9 , further comprising:
 d) instructions for depositing the solution onto a growth surface of the container, allowing the methanol to evaporate and form a calcium lactate precipitate on the growth surface, and coating the calcium lactate precipitate with a liquid growth medium to form a gelled biological growth medium.   
     
     
         11 . The kit of  claim 9 , wherein the solution comprising calcium lactate and methanol comprises from about 50 to about 350 mg of calcium lactate per gram of low methoxyl pectin. 
     
     
         12 . The kit of  claim 9 , wherein the solution comprising calcium lactate and methanol further comprises from about 2% to about 5% water by volume. 
     
     
         13 . A culture container for growth of microorganisms, the container comprising a coating of calcium lactate precipitated on a growth surface of the container and a gelled pectin growth medium deposited on the calcium lactate precipitate.