Ethanol production from spent cherry brine.

Spent cherry brine is an acidic byproduct of maraschino cherry processing and typically consists of variable amounts of glucose and fructose of up to 11% fermentable solids, 0.5-1.5% CaCl2, up to 0.4% sulfur dioxide, sorbitol, and lesser amounts of other cherry constituents. Disposal of brine represents a significant cost to processors because of its high biological oxygen demand. As an alternative, brine was tested as a substrate for ethanol production. Initially, the toxic level of sulfur dioxide was reduced by raising brine pH to 8.0 to precipitate calcium sulfite. Because alkalinization was subsequently found to result in a 10-fold reduction in phosphorous, brines were titrated with phosphoric acid to pH 6.0 prior to inoculation with Saccharomyces cerevisiae. All strains of Saccharomyces cerevisiae tested were able to ferment all lots of Ca(OH)2-treated and phosphorous-enriched brines efficiently. One lot of brine containing 10% (w/v) fermentable sugar yielded 4.7% (w/v) ethanol in 4 days.