Isolation Of Azotobacteria And Effects Of The Inoculants On Crude Protein Content In Products Of Potato Processing Waste Fermentation

Potato residues and the juice as the by-product of the starch production process contain a lot of hard-degradable cellulose and lignin in starch factories. These hard-degradable ingredients and other substances can not be directly used, made them difficult to disposal as wastes. However, they are also important renewable resources to some extent. In recent years, the potato residues and juice are often used as feedstock of animal forages, which can not completely solve the problem. Because nutritional ingredients such as crude protein are in low levels, resulting that the animal feed is of poor nutritional value and palatability.Previous studies showed that when the potato residues and juice are fermented with inoculating mixed microbes of Aspergillus niger,Bacillus pumilus and Candida utilis(1:7:2), a certain improvement of the crude protein content is showed in the fermented products, the nitrogen content of which, nevertheless, can not meet the requirements of animal feed. Because in this approach, the microbes enhanced the crude protein contend of fermentation products by degradation and transformation, but total nitrogen is constant in fermentation. Azotobacteria can intake the nitrogen from the air and transform into the nitrogen resources. Therefore, it will make an improvement on nutritional value of the fermented products using the azotobacteria and the mixed microbes together. This research was based on the prior experiments that the mixed inoculations play an important role in the fermentation of potato residues and juice. We investigated the fermentation process of potato residues with inoculation mixed microbes and azotobacteria, analyzd the effect of adding azotobacteria, and optimized the conditions of potato residues fermentation.In our research, a strain with nitrogen fixation from the vegetable garden near the campus was isolated (denoted as H strain) at the beginning, the ITS sequences of which was identified sequentially, exhibiting the closest relationship with Azotobacter chrococcum of the genus Azotobacter and had 98% homology. After that we made the physiological and biochemical identification of H strain, and ascertained that H strain is A. chrococcum.The co-culture experiments between mixed inocula and A. chrococcum showed that they do not inhibit each other's growth. Due to the better effect of fermentation,We selected the inoculation ratio that A. chrococcum: mixed microbes is 0.5:1, and achieved the new mixed inocula and inoculation ratio 5:1:2:7 as A. chrococcum: A. niger: Candida utilis: B. pumilus. We analyzed the fermentation effect of potato residues and juice by adding the new mixed inoculums and optimized its conditions; the experiments showed that when the fermentation temperature was 40℃, the proportion of dry matter in substrate was 3% and pH 7.0, the fermentation had the best effect. In this condition, the amount of dry fermentation product containing 36% crude protein increased by 100% compared with dry potato residues, in the same way, had a 38.5% improvement than the fermentation with original mixed inoculums. This research provided theoretical basis and important parameters for using A. chrococcum in the fermentation process of potato residues and increasing the crude protein amount of the fermentation products by a large margin. We presented a feasible biological-treatment method as well to transform the fermentation products into animal feed and enhance the nutritional value in animal feed.