Design of automatic multi-layer tumbling horizontal fermentation bed and fermentation experiment

Abstract: To achieve high-value bio-products, solid-state fermentation (SSF) is a sustainable alternative for bio-based processes, in which agro-industrial by-products may be used as culture media or substrates. As a traditional fermentation technology, it has some disadvantages in condition control, industrial enlargement, energy consumption and large floor area, which make it difficult to obtain industrial production line and adapt to the large-scale developmental need of the fermentation industry. In order to solve these problems, using the concept of modern industrial design combined with the mechanized and automatic control technology, the solid fermentation equipment for sterilization, inoculation, mixing and fermentation was designed. Based on this device, the solid fermentation production system which integrates raw material pre-treatment, batching, fermentation and drying, has been formed and successfully put into operation. As the core of production system, the solid fermentation equipment is composed of a scraper feeder, a buffer outlet, a scraper conveyor of the discharge hole and a fermentation chamber with the shape of square column, which is divided into 10 layers (feeder layer is on the top, discharge layer in bottom and 8 fermentation bed layers in the middle) and has 30 m in length, 3 m in width and an area of 50 m2 covered. The materials access to the scraper feeder automatically from hoist hopper, and spread automatically and evenly into the fermentation bed through pendulous feeder. The bottom of each layer is composed of a plurality of platform trap doors which can achieve a 360° forward or reverse turning through computer-controlled cylinder drive. In the fermentation bed, the platform trap doors have turned over one by one from left to right, and the process can be repeated several times until the materials have no residue in the platform trap door. The materials can be transferred effectively from the upper layer to the lower layer, and this process can realize automatic control of temperature and humidity. Using soybean meal as raw material, the experiment of biological feed fermentation was carried out with the system. During the process of fermentation, the moisture of material varied within 38%-42% and the temperature could maintain at 37 ?C, which created a good environment for microbial growth; the moisture and crude protein content could meet the requirements of the product. After 72 h fermentation, the content of acid soluble protein of the feed was increased by 21.2% relatively, and the protein solubility in KOH solution increased from 57.19% to 77.45%. Results showed that the parameters of biological feed met the enterprise standard and the product quality was excellent; the stable operation of the device and large-scale production (production capacity of single batch was 10 t) could meet the needs of industrial production during the process of fermentation. The device has high mechanical automation level and continuous production capacity, which are suitable for the preparation of biological feed, biological fertilizer, biological pigment, biological pesticide, biological fuel and biological enzyme and other fields. As the largest automatic SSF production line, the device can not only ferment biomass materials on a large scale, but also be suitable for the production of a variety of products. It has the features of high degree of automation, less pollution and low energy consumption, which can promote significantly biomass conversion industry in China.