Fermentations inhibition

Therefore, routine application of adequately sensitive test kits is required to avoid major losses due to presence of undetected but fermentation-inhibiting residues in milk. 

The same conditions also resulted in the maximum glucose yield, 17.2 g/ 100 g of SFF. At the pretreatment conditions used, the formation of fermentation-inhibiting compounds was very low (results not shown) (16). The concentration of furfural in the slurry pretreated at 190°C for 10 min was about 0.3 g/L. No HMF was detected. 

To evaluate the degree of microbial growth inhibition caused by the hydrolysate used, Debaryomyces hansenii was grown in detoxified hydrolysates and in a hydrolysate only subjected to a pH correction, both nonsupple-mented and supplemented. As detoxification methods, anion-exchange resins and activated charcoal treatments were chosen because both enable the reduction of most of the fermentation-inhibiting compounds (7,38,39). 

Botrytis Effect on Fermentation. Peynaud et al. (28) suggest that Botrytis cinerea ( noble rot ) produces a substance that inhibits yeast activity. While this substance has not been isolated in the United States, it has been the author s observation that botrytis-infected grapes ferment at a slower rate and have more difficulty completing fermentation. This fermentation inhibition also may be attributable to the higher initial °Brix and, later, to the ethanol and higher residual sugar content of the botrytized wines. 

The production of elfamycins is described in the references cited in Table 1. Fermentation yield improvements with aurodox (1, R = CH ) proved difficult because of feedback inhibition (48). Aurodox-resistant strains (49), however, responded positively to conventional mutagenic methods leading to yield increases from 0.4 to 2.5 g/L (50). Scale-up of efrotomycin (7, R = CH ) fermentations were found to be particularly sensitive to small changes in sterilization conditions of the oil-containing medium used (51). 

Carbon dioxide generated by the fermentation process must be removed to help maintain the pH of the solution at pH 7.6—8.0. Carbon dioxide also inhibits the activity of the bacteria. The oxidation reduction potential is kept at 100—200 mV. The ideal temperature in the reactor varies with different strains in the bacteria but generally is 25—35°C. 

The converted mash is pumped to a clean sterilised fermentor and the yeast inoculum is added. The set temperature range for whiskey fermentation of 72 hours is usually 17—21°C. At the beginning, the mash converted composition is approximately 80% sugars, mainly maltose and some (<1%) dextrose (primary conversion). The pH is adjusted to reduce initial bacterial growth. Grain neutral spidts are usually set at 27—29°C to expedite fermentation. Temperatures above 35°C inhibit yeast reproduction and promote rapid bacterial growth. Above 40°C actual yeast kill occurs. 

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