Value-Added Recycling of Distillation Remnants of Kuma Shochu: A Local Traditional Japanese Spirit, with Photosynthetic Bacteria

Abstract

Kuma Shochu is a traditional spirit produced from rice in Kuma and Hitoyoshi areas, Kumamoto, Japan. Currently, the distillation remnants of Kuma Shochu are concentrated and recycled as fertilizer and animal feeds, which are relatively low-value materials (about $50 per ton). The distilleries’ cost for recycling is more than $100 per ton of the distillation remnants, and this cost is a financial burden for the distilleries. For more value-added use of the distillation remnants, we proposed that the distillation remnants be used to provide culture nutrients for photosynthetic bacteria (PSB), which has ability to promote the growth of plants and can be applied to various agricultural practices. We screened 22 PSB strains for growth in the diluted distillation remnants of Kuma Shochu and successfully isolated 4 PSB strains that grew well without any additives. The effectiveness of the PSB cultured in the distillation remnants (Kuma PSB) was examined with field experiments by the agricultural high school students in the region, and their results indicated that the fresh weights of cabbage, Chinese cabbage, broccoli, and Japanese radish were significantly increased by the PSB treatment. We used these PSB strains to start a university-student-run business venture for manufacturing and distributing the Kuma PSB to local farmers. The present study is the first example of the use of PSB for the recycling of distillation remnants of spirits, and can widely be applied to various spirit industries in the world.