Application one,
A method for increasing the yield of pullulan by double-stage temperature control and adding Tween 60. During the fermentation and cultivation of Aureobasidium pullulans, when the growth of the bacteria is in the adaptation period (fermentation liquid OD620<0.5), control The temperature is 32°C. When the growth of the bacteria is in the early logarithmic phase (OD620 of the fermentation broth ≥ 0.5), the temperature is controlled to 28°C, and Tween 60 with a volume of 0.08%-0.12% of the fermentation broth is added to shorten the fermentation cycle and fermentation time. It is 58-63h. This method increases the yield of pullulan polysaccharide according to the different optimal growth temperatures of the bacteria in different growth cycles and the addition of an appropriate amount of Tween 60 to the bacteria when synthesizing secondary metabolites. The method is convenient to operate and has obvious effects, greatly shortening the fermentation cycle , improve the conversion rate of the substrate, and reduce the cost of pullulan.
Application two,
A gold nanometer colorimetric method for detecting lipase activity in rice bran. It utilizes Tween 60 to modify nano-gold, and in the presence of lipase in rice bran, it hydrolyzes the carboxylate bond of Tween 60, thereby weakening the steric electrostatic repulsion of Tween 60, thereby shortening the distance between nano-gold distance, making it gather blue. It solves the problems of complicated process, high cost, slow detection speed and low sensitivity of the current traditional detection method of lipase activity in rice bran. The steps of the invention are as follows: use Tween 60 to modify nano-gold, construct a nano-gold colorimetric sensor, establish a standard curve with lipases with different activities, and apply it to detect the lipase activity in rice bran. The ratio of absorbance at 650nm and 520nm and lipase activity in rice bran showed a good linear relationship in the range of 0.02-1.8mg/mL, and the detection limit was 2.56×10?4mg/mL (S/N=3). This process does not require sample pretreatment, has strong specificity and high sensitivity, and can detect lipase activity in the rice bran production process in real time.
