Construction of Recycling System for Sugarcane-Derived Wastes by Incorporating Mushroom Cultivation

Abstract

Brown sugar shochu is the spirits produced in the Amami Islands, southern Japan. The waste lees (deposits of yeast and other particles) from shochu production amounts to 10,000 tons per year. A feature of shochu lees is the high potassium (K) content (5.2 g per 100 g dry weight). Brown sugar is imported for the production of brown sugar shochu because of its low cost, however, the disadvantage of this practice is the occurrence of excessive K in the farmland. The lees are usually sprinkled on local sugarcane fields where K accumulates in the soil. This excess K is likely to reduce sugar production by the cane, risking local core industries. On the other hand, bagasse fibers that remain after sugar extraction amounts to 100,000 t per year and have been used as fuel. Therefore, in order to stimulate the local economy and stabilize the sugarcane production in the Amami islands, it is essential to device new, high-value added products based on the lees and bagasse, by-products of local industries.

In this study, we tried effective waste disposal by using the two by-products for mushroom cultivation. Brown sugar shochu lees contain high level of nitrogen-free extracts and minerals including K, and these nutrients are required for the cultivation of mushroom. The bagasse was spontaneously fermented for 1-2 months indoors. The fermentation partially degrades refractory organic matters such as cellulose, lignin, and other high molecular compounds, which turns the bagasse to soft, air-permeable materials with storability. The combined usage of the two sugarcane by-products were good for the production of Jew’s ear mushroom (Auricularia polytricha).

1) When cultivating mushrooms in the media with fermented bagasse and brown sugar shochu lees, the synergistic effect of both materials was able to produce the mushroom more efficiently than conventional medium.

2) In the medium with 5% or more of the shochu lees, the mushroom production was better than that of the conventional medium, and the optimum medium for the production was bagasse 85% and shochu lees 10%.

3) In the medium using both wastes, the fruitbody production period could be drastically reduced by the high humidity control inside the generation room.

4) Fruitbodies produced in media using both wastes were rich in dietary fiber than those produced in conventional media. In addition, β-glucan content of some fruitbodies increased by 30% or more. For these reasons, highly functional fruitbodies have high added value judged as regional special products.

Keywords: Auricularia polytricha, Shochu lees, Mushroom cultivation, Sugarcane-derived wastes