Production of fatty acids by engineered Ogataea polymorpha / 生物工程学报

Fatty acids (FA) are widely used as feed stocks for the production of cosmetics, personal hygiene products, lubricants and biofuels. Ogataea polymorpha is considered as an ideal chassis for bio-manufacturing, due to its outstanding characteristics such as methylotroph, thermal-tolerance and wide substrate spectrum. In this study, we harnessed O. polymorpha for overproduction of fatty acids by engineering its fatty acid metabolism and optimizing the fermentation process. The engineered strain produced 1.86 g/L FAs under the optimized shake-flask conditions (37℃, pH 6.4, a C/N ratio of 120 and an OD600 of seed culture of 6-8). The fed-batch fermentation process was further optimized by using a dissolved oxygen (DO) control strategy. The C/N ratio of initial medium was 17.5, and the glucose medium with a C/N ratio of 120 was fed when the DO was higher than 30%. This operation resulted in a titer of 18.0 g/L FA, indicating the potential of using O. polymorpha as an efficient cell factory for the production of FA.

High cell density culture of an engineered yeast strain for sclareol production / 生物工程学报

Cell growth profiles were evaluated in shake-flask culture to improve sclareol production by the engineered yeast strain Saccharomyces cerevisiae S7. Product formation was tightly coupled with cell growth. High cell density cultures were performed with different carbon sources using a dissolved oxygen level feedback-control strategy in a 3 L bioreactor. The titers of sclareol were 253 mg/L, 386 mg/L and 408 mg/L, respectively, when glucose, ethanol and glucose/ethanol mixture were used as the carbons sources. The maximal titer was 27-fold higher than that obtained under shake-flask culture conditions. The results suggested that the presence of ethanol was beneficial to sclareol production. These results provided useful information for optimization of yeast cell factory and efficient production of terpenoids.

Beta-1,3-glucomannanase assisted lipid extraction from Rhodosporidium toruloides / 生物工程学报

To evaluate the effectiveness of enzymatic assisted extraction (EAE) of lipid from the oleaginous yeast Rhodosporidium toruloides in the presence of beta-1,3-glucomannanase at a larger scale, we investigated the effects of enzymatic treatment and extraction conditions on lipid extraction yields at 10-L scale by using the broth of R. toruloides Y4 as the feed and ethyl acetate as the solvent. When it was treated for 0.5 h, the lipid extraction yield reached 71.1%, indicating that the enzymatic treatment process reached similar efficiency to that obtained at 10-mL scale. The inhibitory effect of emulsification was greatly reduced by repeated extraction. After extracted for three times, yields of lipid extraction, solvent recovery and total material recovery reached 92.9%, 87.0% and 94.2% respectively. As it can use the lipid production slurry with good extraction efficiency, EAE technology is promising for industrial production of microbial lipids.

Effects of dilution rate and carbon-to-nitrogen ratio on lipid accumulation by Rhodosporidium toruloides under chemostat conditions / 生物工程学报

The objective of this work is to investigate how dilution rate and carbon-to-nitrogen (C/N) ratio affects lipid accumulation by Rhodosporidium toruloides AS 2.138 9 in continuous culture. Under steady-state conditions, the increase in dilution rate led to the decrease in lipid content and lipid yield. The highest lipid yield and lipid content at D = 0.02 h(-1) were 0.18 g lipid/g sugar and 57.1%, respectively, while the highest lipid productivity and biomass productivity were obtained at D = 0.14 h(-1). The increase in C/N ratio led to the increase in lipid content. The highest lipid content of 38% was obtained at C/N = 237. The highest lipid yield of 0.12 g lipid/g sugar was obtained at C/N = 92. However, the highest lipid productivity of 0.12 g/(L x h) was obtained at C/N = 32. No significant changes were observed in terms of fatty acid composition of the lipid produced under different C/N ratios, and these three fatty acids, palmitic acid, stearic acid and oleic acid, took over 85% in all samples.

Clinical application of immediate latissimus dorsal myocutaneous flap in breast reconstruction after partial re-moval of breast / 中华医学美学美容杂志

Objective To study the immediate conservative breast surgical reconstruction by trans-ferring the same lateral latissimus dorsal myocutaneous flap (LDM) for the treatment of stage Ⅱ and stage Ⅲ breast cancer, combined with neoadjuvant chemotherapy. Methods Breast cancer patients in stage Ⅱ and Ⅲ with pathological diagnosis by core needle biopsy, had undergone immediate conservative breast reconstruction surgery with transferring the latissimus dorsal myocutaneous (LDM). We scored the reconstructed breast twice at one month after operation and completion of radiation. The final score was decided using the mean value of the twice evaluating score. Kaplan-Meier survival was used to analyze the survival of 18 cases with traditional mastectomy. Results The tumor size ranged from 30 mm to 55 mm before neoadjuvant chemotherapy, and ranged from 25mm to 45 mm after neoadjuvant chemotherapy. The median weight of the tumor specimens in breast conservative operation was 140 g (90 g to 220 g). A-mong the 18 patients, 16 cases had more than 3 scores with satisfied cosmetics (93.33 % ). Dorsal subcu-taneous seroma in donation area was observed in 5 of 18 patients (27.78 %) and dorsal incision dehiscence was observed in 2 of 18 patients (11.11%). None of the patients developed recurrence except that 1 pa-tient (5.55 %) had distance metastasis (bone metastasis} in a mean 22-months follow-up. The Kaplan-Meier survival curve in breast conservation reconstruction patients had no different from that of traditional mastectomy patients at the same time. Conclusions Immediate conservative breast surgical reconstruction by using the same lateral latissimus dorsal myocutaneous flap is an effective method for stage Ⅱ and stage Ⅲ breast cancer patients combined with neoadjuvant chemotherapy, which can increase satisfactory breast so that cosmetic outcome can be reached.