The fermentation of cell wall substances in grass silage and in potato pulp

Summary The amount of acid formed in grass silage was greater than could have been formed from the soluble sugars present, even when only a lactic fermentation took place. This seemed to point to fermentation of cell wall substances by lactic acid bacteria. Lactic acid fermentation in potato pulp always takes place with cell wall substances as substrates, as sugars are absent. It was found that galactose, probably occurring as galactan, and also some pectic acid were fermented in potato pulp. Some lactobacilli were isolated from potato pulp; streptobacteria which could ferment galactan but no pectic or galacturonic acid, and betabacteria which could ferment galacturonic acid but no galactan or pectic acid. A number of homofermentative lactobacilli were all found to belong to the speciesStreptobacterium casei. It was shown that a strain of this species could ferment galactan in potato pulp sterilised previously with ethylene oxide. Part of this work was carried out at the Netherlands Institute for Dairy Research, Ede, Netherlands.