Optimizing the Conditions of Pretreatment and Enzymatic Hydrolysis of Sugarcane Bagasse for Bioethanol Production.

The agricultural waste sugarcane bagasse (SCB) is a kind of plentiful biomass resource. In this study, different pretreatment methods (NaOH, H2SO4, and sodium percarbonate/glycerol) were utilized and compared. Among the three pretreatment methods, NaOH pretreatment was the most optimal method. Response surface methodology (RSM) was utilized to optimize NaOH pretreatment conditions. After optimization by RSM, the solid yield and lignin removal were 54.60 and 82.30% under the treatment of 1% NaOH, a time of 60 min, and a solid-to-liquid ratio of 1:15, respectively. Then, the enzymolysis conditions of cellulase for NaOH-treated SCB were optimized by RSM. Under the optimal enzymatic hydrolysis conditions (an enzyme dose of 18 FPU/g, a time of 64 h, and a solid-to-liquid ratio of 1:30), the actual yield of reducing sugar in the enzyme-treated hydrolysate was 443.52 mg/g SCB with a cellulose conversion rate of 85.33%. A bacterium, namely, Bacillus sp. EtOH, which produced ethanol and Baijiu aroma substances, was isolated from the high-temperature Daqu of Danquan Baijiu in our previous study. At last, when the strain EtOH was cultured for 36 h in a fermentation medium (reducing sugar from cellulase-treated SCB hydrolysate, yeast extract, and peptone), ethanol concentration reached 2.769 g/L (0.353%, v/v). The sugar-to-ethanol and SCB-to-ethanol yields were 13.85 and 11.81% in this study, respectively. In brief, after NaOH pretreatment, 1 g of original SCB produced 0.5460 g of NaOH-treated SCB. Then, after the enzymatic hydrolysis, reducing sugar yield (443.52 mg/g SCB) was obtained. Our study provided a suitable method for bioethanol production from SCB, which achieved efficient resource utilization of agricultural waste SCB.

The effect of PK gene overexpression on content and antioxidant properties of carotenoids in marine microalga Dunaliella parva.

Dunaliella parva can extensively accumulate carotenoids, which is a promising raw material for carotenoids production. Carotenoids have important medicinal value. D. parva is an ideal organism for studying the mechanism of carotenoid synthesis. Our previous study identified a transcription factor DpAP2 which could regulate carotenoid synthesis in D. parva. In addition, DpAP2 could interact with three proteins with different activities (DNA binding transcription factor activity, protein kinase activity, and alpha-D-phosphohexomutase). To investigate the function of PK gene encoding interacting protein of DpAP2 with protein kinase activity in D. parva, PK gene was cloned into vector pBI221-GFP-UbiΩ-CAT and transformed into D. parva in this study. The results showed that overexpression of PK gene enhanced the contents of carotenoids, total sugars, proteins, and antioxidant activities of carotenoid extract such as superoxide radical scavenging activity, reducing power, hydroxyl radical scavenging activity in transgenic D. parva with overexpression of PK gene. This study explored the function of PK gene, and improved the medicinal value of D. parva.