Prevention of bacterial growth in fermentation process

Abstract

A fermentation process for the production of ethanol from natural sources, such as corn, comprising introducing a fermentable sugar, an inoculant, and a stabilized chlorine dioxide into a fermentation system is disclosed. The stabilized chlorine dioxide is added preventatively to the fermentation system, at concentrations in the fermentation system of acetic acid no greater than 0.30% (weight/volume) and lactic acid no greater than 0.60% (weight/volume). The stabilized chlorine dioxide is added in an amount effective to substantially prevent growth of bacteria.

1 . A process to substantially prevent the growth of bacteria in a fermentation system comprising introducing a fermentable sugar, an inoculant and a stabilized chlorine dioxide into a fermentation system wherein the inoculant converts the sugar to ethanol and carbon dioxide; wherein the stabilized chlorine dioxide is added, in an amount effective to substantially prevent growth of bacteria, to one or more of the fermentable sugar, the inoculant, or the fermentation system at concentrations in the fermentation system of acetic acid no greater than 0.30% (weight/volume) and lactic acid no greater than 0.60% (weight/volume), and further wherein the amount of stabilized chlorine dioxide added is from about 0.0001 to about 5%, based on the weight of activated chlorine dioxide which can be produced and the total weight of the fermentation system. 
   
   
       2 . The process of  claim 1  wherein the stabilized chlorine dioxide is added to the fermentable sugar. 
   
   
       3 . The process of  claim 1  wherein the stabilized chlorine dioxide is added to the inoculant. 
   
   
       4 . The process of  claim 1  wherein the stabilized chlorine dioxide is added to the fermentation vessel. 
   
   
       5 . The process of  claim 4  wherein the stabilized chlorine dioxide is added before addition of fermentable sugar or before addition of inoculant to the fermentation system. 
   
   
       6 . The process of  claim 1  wherein the stabilized chlorine dioxide is added in an amount from about 0.01% to about 3% based on the weight of activated chlorine dioxide which can be produced and total weight of the contents of the fermenter. 
   
   
       7 . The process of  claim 6  wherein the stabilized chlorine dioxide is added in an amount from about 0.1% to about 2% based on the weight of activated chlorine dioxide which can be produced and total weight of the contents of the fermenter. 
   
   
       8 . The process of  claim 1  wherein the stabilized chlorine dioxide is a chlorine dioxide-containing oxy-chlorine complex which is a complex of chlorine dioxide with carbonate, chlorine dioxide with bicarbonate or a mixture thereof. 
   
   
       9 . The process of  claim 1  wherein the stabilized chlorine dioxide is a chlorite-containing component, which is one or more metal chlorites. 
   
   
       10 . The process of  claim 8  wherein the metal chlorite is an alkali metal chlorite or an alkaline earth metal chlorite. 
   
   
       11 . The process of  claim 9  wherein the metal chlorite is sodium chlorite. 
   
   
       12 . The process of  claim 1  wherein the stabilized chlorine dioxide is provided in a liquid medium at a concentration having a potential concentration of activated chlorine dioxide in the range of about 0.002% to about 40% by weight, based on the total weight of the liquid medium. 
   
   
       13 . The process of  claim 12  wherein the stabilized chlorine dioxide is provided in a liquid medium at a concentration having a potential concentration of activated chlorine dioxide in the range of about 2% to about 25% by weight, based on the total weight of the liquid medium. 
   
   
       14 . The process of  claim 12  wherein the stabilized chlorine dioxide is provided in a liquid medium at a concentration having a potential concentration of activated chlorine dioxide in the range of about 5% to about 15% by weight, based on the total weight of the liquid medium. 
   
   
       15 . The process of  claim 1  wherein the inoculant is yeast. 
   
   
       16 . The process of  claim 15  wherein the inoculant is added in an amount of about 1 pound of dry yeast per 1000 gallons (1 kilogram per 8000 liters) of composition comprising fermentable sugar. 
   
   
       17 . The process of  claim 15  wherein the fermentable sugar is derived from one or more of one or more corn, wood chips, wheat straw, corn stover, switch grass, milo, barley, millet, sorghum, sugar cane, sugar beets, molasses, whey, potatoes. 
   
   
       18 . The process of  claim 17  wherein the fermentable sugar is derived from corn. 
   
   
       19 . The process of  claim 18  wherein the fermentable sugar is present in the fermentation system in a concentration of about 5 to about 40% (weight/volume). 
   
   
       20 . The process of  claim 19  wherein the fermentable sugar is present in the fermentation system in a concentration in the range of about 10 to 35% (weight/volume). 
   
   
       21 . The process of  claim 15  wherein the stabilized chlorine dioxide is added to the fermentation system prior to addition of the inoculant. 
   
   
       22 . The process of  claim 1  wherein the fermentable sugar is derived from corn and is present in the fermentation system in a concentration in the range of about 10 to 35% (weight/volume); the inoculant is yeast; the stabilized chlorine dioxide is added to the fermentation system before addition of fermentable sugar or before addition of inoculant to the fermentation system; the stabilized chlorine dioxide is added in an amount from about 0.01% to about 3% based on the weight of activated chlorine dioxide which can be produced and total weight of the contents of the fermenter; the stabilized chlorine dioxide is an alkali metal chlorite or an alkaline earth metal chlorite, which is provided in a liquid medium at a concentration having a potential concentration of activated chlorine dioxide in the range of about 2% to about 25% by weight, based on the total weight of the liquid medium.