Reutilization And Reduction Of Semi-solid Waste Pichia Pastoris Based On ABE Fermentation

Semi-solid waste Pichia pastoris having high cells density is a typical industrially-waste biomass with huge treating difficulty.However,it enriches with carbohydrates/proteins,and could be efficiently digested and reutilized by anaerobic fermentation processes.In this thesis,by properly pre-treating the semi-solid waste to form suitable suspensions and then implementing ABE fermentation using corn-starch/the waste suspensions as the substrate,raising the efficiencies of sugar utilization,ABE concentration,and waste yeast reutilization/reduction was attempted.At the same time,the problems of high raw materials cost and operation lose in ABE fermentation process was also tried to solve.The major results of the thesis were summarized as follows:1)The pre-treating manner as well as initial corn-starch amount,waste yeast and NaOH usage doses were optimized.The optimized amount or usage doses were 8%,80 g·L^-1 and 6¹0 g·L^-1,respectively.2)The ABE fermentations were carried out in 100 mL anaerobic bottles based on the above optimized results.Compared with the control groups,the total sugar utilization efficiency increased from about 40%to over 90%,and 57%corn-starch usage dose was saved,butanol concentration reached and stabilized around 10.63¹1.70 g·L^-1,which was 92.92%¹12.31%higher than that obtained with 8%corn-starch based substrate.3)Dynamic?concentrations?changes of the fermentation parameters such as targeted products,amino acids,total sugar/oligosaccharides,CO₂,organic acids,ammonia nitrogen,NH₄⁺,urea and SO₄^2-were analyzed in a 7 L static anaerobic fermentor.The results indicated that after supplementing the waste suspensions,the effective utilizations of disaccharides/trisaccharides accounted for the big increase in total sugar utilization efficiency,and the solvent concentration is greatly increased.In this way,not only the resource utilization of the corn-starch is greatly increased,but also the recycling of the waste P.pastoris is realized.4)In the ABE fermentation system under mixed substrate conditions,total organic acids reached a high level of 3.51 g·L^-1 and the maximum liquefaction rate of waste yeast is about11%;Total gas production is also greatly increased,and the maximum CO₂ gasification rate of48%originated from the waste yeast was obtained,which greatly contributed to the waste yeast reduction?gasification+liquefaction?.5)The relationship between total ABE concentrations and carbohydrate utilization rate in waste yeast when using corn-starch/waste yeast suspension mixture as the substrate was investigated.The results showed that the carbohydrate utilization rate could reach a high level of 65%while ABE concentration stayed at lower level of 14 g·L^-1 when processing 40 g·L^-1waste yeast;on the contrary,the carbohydrate utilization rate stayed about 52%but ABE concentration reached a higher level of 18 g·L^-1 when processing 80 g·L^-1 waste yeast.The analysis basically coincided with the experimental data,and it is possible to freely set/regulate the required total ABE concentration and carbohydrate utilization rate.