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( Sheng Rong Liu ),( Qing Ping Wu ),( Ju Mei Zhang ),( Shu Ping Mo ) 한국미생물 · 생명공학회 2015 Journal of microbiology and biotechnology Vol.25 No.3
ε-Poly-L-lysine (ε-PL) is a homopolymer of L-lysine molecules connected between the epsilon amino and alpha carboxyl groups. This polymer is currently used as a natural preservative in food. Insufficient biomass is a major problem in ε-PL fermentation. Here, to improve cell growth and ε-PL productivity, various nitrogen-rich nutrients were supplemented into flask cultures after 16 h cultivation, marking the onset of ε-PL biosynthesis. Yeast extract, soybean powder, corn powder, and beef extract significantly improved cell growth. In terms of ε-PL productivity, yeast extract at 0.5% (w/v) gave the maximum yield (2.24 g/l), 115.4% higher than the control (1.04 g/l), followed by soybean powder (1.86 g/l) at 1% (w/v) and corn powder (1.72 g/l) at 1% (w/v). However, supplementation with beef extract inhibited ε-PL production. The optimal time for supplementation for all nutrients examined was at 16 h cultivation. The kinetics of yeast-extract-supplemented cultures showed enhanced cell growth and production duration. Thus, the most commonly used two-stage pH control fed-batch fermentation method was modified by omitting the pH 5.0-controlled period, and coupling the procedure with nutrient feeding in the pH 3.9-controlled phase. Using this process, by continuously feeding 0.5 g/h of yeast extract, soybean powder, or corn powder into cultures in a 30 L fermenter, the final ε-PL titer reached 28.2 g/l, 23.7 g/l, and 21.4 g/l, respectively, 91.8%, 61.2%, and 45.6% higher than that of the control (14.7 g/l). This describes a promising option for the mass production of ε-PL.
Sheng-Rong Liu,Wei-Rui Zhang 한국식품과학회 2018 Food Science and Biotechnology Vol.27 No.4
To facilitate Ganoderma lucidum submerged culture and obtain high productivity, a fine powder of wheat bran was used to grow the fungus for solid-state fermentation and as solid seed for its submerged cultures. The results indicated that the optimal inoculum size was low, being 0.75 g in 250 mL-sized flasks containing 80 mL medium. The maximal exopolysaccharide concentration and biomass produced was 0.74 and 14.71 g/L, respectively, which is considerably higher than that obtained with the commonly used mycelial pellet liquid seed (0.47 and 8.56 g/L, respectively). The EPS and biomass productivity of the solid seed cultures decreased only slightly, even after a 6-month storage period. EPS produced showed higher antioxidant activity compared with that produced in the liquid seed cultures. The developed solid seed can serve as a ready-to-use inoculum for long-term use in G. lucidum submerged culture for the hyperproduction of highly bioactive EPS and biomass.
Sheng-Rong Liu,Wei-Rui Zhang 한국식품과학회 2019 Food Science and Biotechnology Vol.28 No.4
To facilitate Ganoderma lucidum submergedcultivation and achieve high productivity, four fine powdersolid substrates incorporated with different nitrogen-richsupplements were utilized to grow the fungus and as solidseed for its submerged culture. Of the four solid seeds, thesoybean meal solid seed gave the highest biomass (10.73 g/L) and exopolysaccharide (EPS) (1.22 g/L), higher thanthose (8.36 g/L biomass and 0.44 g/L EPS) obtained withmycelial liquid seed. The optimal level of soybean mealsupplementation was 20% (w/w) for production of the solidseed. Following single factor experiments, levels of threeselected process variables were optimized as: the moisturecontent of solid seed, 70%; inoculum size, 0.8 g/flask; androtary speed, 160 rpm. These conditions were validatedexperimentally with improved EPS yield of 1.33 g/L. Thedeveloped solid seed can be conveniently used for G. lucidumsubmerged culture with improved EPS productivity.
( Liu Sheng Rong ),( Qing Ping Wu ),( Ju Mei Zhang ),( Shu Ping Mo ),( Xiao Juan Yang ),( Chun Xiao ) 한국미생물 · 생명공학회 2012 Journal of microbiology and biotechnology Vol.22 No.9
ε-Poly-L-lysine (ε-PL), produced by Streptomyces or Kitasatospora strains, is a homo-poly-amino acid of Llysine, which is used as a safe food preservative. The present study investigates the combined use of cell immobilization and in situ adsorption (ISA) to produce ε-PL in shaken flasks. Loofah sponge-immobilized Streptomyces ahygroscopicus GIM8 produced slightly more ε-PL than those immobilized on synthetic sponge, and sugarcane bagasse. Moreover, loofah sponge supported the maximum biomass. Hence, loofah sponge was chosen for cell immobilization. Meanwhile, the ion-exchange resin D152 was employed for ISA. The loofah sponge-immobilized cells produced 0.54 ± 0.1 g/l ε-PL, which significantly increased to 3.64 ± 0.32 g/l after combining with ISA through the addition of resin bags. The free cells with ISA using the dispersed resin yielded 2.73 ± 0.26 g/l of ε-PL, an increase from 0.82 ± 0.08 g/l. These data illustrate that the proposed combination method improved production most significantly compared with either immobilization or ISA only. Moreover, the immobilized cells could be repeatedly used and an ε-PL total amount of 8.05 ± 0.84 g/l was obtained. The proposed combination method offers promising perspectives for ε-PL production.
Analysis and Design of a New Topology of Soft-Switching Inverters
Rong Chen,Jia-Sheng Zhang 전력전자학회 2013 JOURNAL OF POWER ELECTRONICS Vol.13 No.1
This paper proposes the power conversion mechanism of a bailer-charge-transfer zero-current-switching (CT-ZCS) circuit. The operation modes are analyzed and researched using state trajectory equations. The topology of CT-ZCS based on soft-switching inverters offers some merits such as: tracking the input reference signal dynamically, bearing load shock and short circuit, multiplying inverter N+1 redundancy parallel, coordinating power balance for easy control, and soft-switching commutation for high efficiency and large capacity. These advantages are distinctive from conventional inverter topologies and are especially demanded in AC drives: new energy generation and grid, distributed generation systems, switching power amplifier, active power filter, and reactive power compensation and so on. Prototype is manufactured and experiment results show the feasibility and dynamic voltage-tracking characteristics of the topology.