certain species of lactobacillus ferment glucose into mainly lactic acid in a process termed fermentation, while other species of lactobacillus ferment a mixture including lactic acid, acetic acid and carbon dioxide in a process termed heterolactic fermentation.certain species of lactobacillus ferment glucose into mainly lactic acid in a process termed fermentation, while other species of lactobacillus ferment a mixture including lactic acid, acetic acid and carbon dioxide in a process termed heterolactic fermentation.