Papers by Author: Ge Yang

Abstract: Air pressure amplitude serves as a critical control parameter in periodic pressure solid state fermentation process. Effects of air pressure amplitudes on thermostable xylanase production by Thermomyces lanuginosus SD-21 were investigated. Under the optimum periodic pressure amplitude, namely: at lower limit of 0.05 MPa and upper limit of 1.5 MPa. Among the lignocellulosic substrates tested, corn cob and wheat bran supported a high xylanase (EC 3.2.1.8) secretion by Humicola lanuginosa in solid-state fermentation (SSF). Enzyme production reached a peak in 96 h followed by a decline thereafter. Enzyme production was very high, xylanase activity 8237 IU /g of dry moldy bran can be obtained in the system compared with 4520 IU/g in conventional tray fermenter, cultivation of the mold in large enamel trays yielded a xylanase titer comparable with that in flasks. Parametric optimization resulted in a 45.13% increase in enzyme production in PPSSF.

Abstract: Poly-γ-glutamic acid (γ-PGA) is a kind of water-soluble and biodegradable polymer, as a potential targeted biopolymer that can be refined from biomass directly. In this work, the effect of environmental parameters on γ-PGA formation by Bacillus licheniformis is investigated . The influence of culture temperature, pH and culture time on cell growth, γ-PGA production and molecular weight, polymer stereochemistry are determined. The γ-PGA yield is higher(30.13g/L) at culture temperature 37 , pH 7.0. Alteration of the medium pH, temperature, culture time and aeration had little to no significant effects on the product quality as measured by stereochemical composition. But alteration of the medium pH, temperature, culture time and aeration have obvious effects on the γ-PGA yield and molecular weight, increasing the biomass and γ-PGA yields. Under the optimal environmental conditions yields of γ-PGA in excess of 36g/L is obtained in submerged culture. Finally, the large-scale fermentation of γ-PGA production was successfully scaled up to a 100-l fermentor, with the highest γ-PGA productivity for over 57.5 g/l.

Abstract: We studied a novel bioflocculant poly(γ-glutamic acid) (PGA). With the addition of 4mg/L PGA (Mw=9×10⁵Da) and 12 Mm CaCl₂, the optimal temperature for flocculation performance of PGA in the kaolin suspension was about 30°C, giving the highest flocculating activity of 98%, respectively. Studies of the flocculating properties revealed that it was stable at 30-90°C and pH 7-11. With treatment of jean dyeing wastewater flocculation, PGA showed that the color, COD, NH₃-N, alkalinity and hardness removal ratios were 90%, 91.7%, 73.3%, 65 % and 86 %, respectively. Bioflocculant PGA may find possible application as an alternative for textile dyeing industry and environmental bioremediation.

Abstract: Docosahexaenoic acid (DHA. C22:6 ω-3) is an important structural component of neural and retinal tissues .The DHA yield was highest at pH5.5. Glucose and maltose utilization were similar as a function of pH, linseed oil consumption increased at pH 5.5, indicating that the formation of DHA from linseed oil at pH5.5 was of increased importance. Increased aeration resulted in doubling of T. aureum cell dry weights, increasing DHA yields and increasing in the maximum DHA -specific production rate .