Optimization Of The Process For Synthesizing Bacterial Cellulose By Fermentation Of Corn Starch Hydrolysate

Bacterial cellulose(BC)is a kind of high-purity cellulose,which is produced by bacteria through a series of fermentation reactions.Compared with plant cellulose,BC has better performance,some excellent special properties,and has a wide range of applications in medical dressings,food,biochemical and other fields.However,in the laboratory research stage and modern industrial production,oligosaccharides such as purified monosaccharides or disaccharides are used as the carbon source of synthetic or semi synthetic medium,so the production cost of bacterial cellulose will be very high,and the output is not high,which has a limiting effect on the application and development of bacterial cellulose.It is an effective way to find a relatively low-cost carbon source as the culture medium for bacterial cellulose production by microbial fermentation and improve the production of bacterial celluloseCorn is the main grain economic crop in China.In China,the output of corn is steadily increasing every year,and the output of corn starch is gradually expanding Corn mainly contains starch,and corn starch is mainly carbohydrate,which is composed of a single structure sugar unit.Therefore,corn starch can be dried,pretreated with citric acid and hydrolyzed with amylase to produce reducing sugar glucose and related oligosaccharides.The treated hydrolysate can be used for the fermentation of Acetobacter xylinum to synthesize bacterial cellulose.In this paper,the hydrolysis technology of corn starch was studied,and the best conditions for the hydrolysis of corn starch to obtain reducing sugar were explored.In this experiment,corn starch hydrolysate was used as the carbon source of Acetobacter xylinum fermentation to synthesize bacterial cellulose.The practicability of batch feeding or continuous fermentation mode to synthesize bacterial cellulose was further exploredIn the process optimization of corn starch hydrolysis,the effects of enzyme dosage,temperature,pH and fermentation time on the yield of reducing sugar produced by corn starch hydrolysis were studied respectively.By selecting several influencing factors at different levels,orthogonal experiments were carried out to explore the optimal hydrolysis conditions of corn starch.The results of orthogonal test showed that the best hydrolysis conditions of corn starch were:reaction temperature 50℃,glucoamylase dosage 60 U/g,pH value 5,hydrolysis time 60 H.According to this condition,the yield of reducing sugar is the highest.This study focuses on obtaining high yield of reducing sugar,which provides enough carbon source for the production of bacterial celluloseIn the study of the production process optimization of bacterial cellulose,corn starch with wide sources and low price is used as the raw material to produce reducing sugar solution through hydrolysis,which is used as the carbon source of bacterial cellulose.Through the preliminary exploration of several single factor experiments,the optimal production process of bacterial cellulose was determined by orthogonal test.In the process of my experimental research,the chemical properties of the fiber were studied,and some characteristics of bacterial cellulose were understood by means of SEM,elemental analysis,infrared analysis and other analytical means This experiment focuses on the effects of several factors such as concentration of corn starch hydrolysate,initial pH,culture temperature,liquid loading and microbial inoculation on yield improvement.Research findings:1.The synthesis of bacterial cellulose is affected by temperature.With the increase of temperature,the synthesis of bacterial cellulose increased first and then decreased.When the fermentation temperature is controlled at 30℃,the production of bacterial cellulose is the highest2.The amount of bacterial cellulose synthesis is affected by the initial pH value The initial pH value was set from slightly acidic to slightly alkaline.The synthesis amount of bacterial cellulose first increased and then decreased with the pH value When the initial pH value is 6,the yield is the highest.3.The amount of bacterial cellulose synthesis is affected by the amount of liquid It was found that the largest amount of bacterial cellulose was synthesized when the liquid content was 75ml in a 250ml volumetric flask.The amount of bacterial cellulose synthesis decreased slowly when the liquid content was more than 75ml4.The amount of bacterial cellulose synthesis was affected by the amount of corn starch hydrolysate.It was found that the synthesis of bacterial cellulose increased with the increase of corn starch hydrolysate.When the increasing amount is 6%,the synthesis amount is the highest.With the increase of corn starch hydrolysate,the amount of bacterial cellulose synthesis began to decrease.5.The synthesis of bacterial cellulose was affected by the inoculation amount of Acetobacter xylinum.After the study,when the inoculation amount of Acetobacter xylinum was 8%,the bacterial cellulose synthesis was the highest,and then the yield was stable.After obtaining the optimal process conditions,the secondary fed batch fermentation was carried out according to the process conditions.The total production of bacterial cellulose increased by 54%.Based on the analysis of the content and pH of reducing sugar in the fermentation waste liquid,the scheme of fed batch fermentation for the fermentation waste liquid was put forward:by adjusting the content of reducing sugar,inoculation amount and pH value of the fermentation waste liquid,the fermentation environment could be improved,and the secondary fermentation of microorganisms could be carried out.It is expected that the continuous production of bacterial cellulose can be realized,the production cost can be reduced and the output of bacterial cellulose can be increased through the secondary feeding fermentation and the possible continuous feeding fermentation.