Improved glucose yield and concentration of sugarcane bagasse by the pretreatment with ternary deep eutectic solvents and recovery of the pretreated liquid

Selective separation of poplar hemicellulose and simultaneous enrichment of soluble xylose in the hydrolysate by itaconic acid pretreatment

Organic-acid pretreatments designed to efficiently separate hemicellulose and preserve high-value soluble monosaccharides in hydrolysates have become a significant research focus. In this study, the efficiency of the catalytic degradation of a lignocellulosic model using itaconic acid (IA) was evaluated. The exceptional selectivity of IA for xylan degradation was confirmed. The separation yield of poplar fractions was assessed after IA pretreatment. The yield of xylose was 81.91 % under the optimal conditions (IA concentration: 5.0 wt%, 160 °C, 60 min). The hydrolysate contained up to 12.10 g/L xylose, exceeding that obtained with formic acid and levulinic acid pretreatments. The simultaneous separation of hemicellulose and protection of soluble sugars was achieved. The high crystallinity index (66.69 %) of the residual solid (RS) confirmed the effective protection of cellulose by IA pretreatment. Additionally, the lignin in the RS contained 53.45 % β-O-4 and 1.21 mmol/g phenolic hydroxyl. This suggests that the IA-pretreated lignin retains more active functional groups, which are advantageous for subsequent conversion and utilization. These findings offer a novel approach for efficient hemicellulose separation and the effective protection of soluble xylose during organic-acid pretreatment.

Transcriptomic profiling of adding cobalt chloride to improve dendrobine-type total alkaloid production

Trichoderma longibrachiatum UN32 is known for its efficient production of dendrobine-type total alkaloids (DTTAs). This study aimed to determine the optimal medium composition for the UN32 strain using response surface methodology. Key factors, including glucose, beef extract, and CoCl2, were selected through the Plackett-Burman design. Subsequently, a factorial optimization approach was employed using the steepest ascent design, and 17 trial sets were completed via the Box-Behnken design. The optimal medium composition was found to consist of 29.4 g/L of glucose, 17.3 g/L of beef extract, and 0.28 mmol/L of CoCl2. This optimized medium resulted in an impressive 80.8% increase in mycelial dry weight (reaching 12.303 g/L) and a substantial 76.4% boost in DTTA production (reaching 541.63 ± 46.95 μg). Furthermore, the fermentation process was scaled up to a 5-L bioreactor, leading to a DTTA production approximately 1.95 times than the control. Transcriptome analysis of strain UN32 in response to CoCl2 supplementation revealed significant changes in the expression of critical genes associated with the TCA cycle and L-valine, L-leucine, and L-isoleucine biosynthesis changed. These alterations resulted in a heightened influx of acetyl-CoA into DTTA production. Additionally, the expression of genes related to antioxidant enzymes was modified to maintain homeostasis of reactive oxygen species (ROS). A potential mechanism for the accumulation of DTTAs based on ROS as a signal transduction was proposed. These findings provide valuable insights into the regulatory mechanisms of DTTA biosynthesis, potentially offering a method to enhance the production of secondary metabolites in the UN32 strain. KEY POINTS: • After the RSM optimization, there is a substantial increase of 80.8% in biomass production and a significant 76.4% rise in DTTA production. • Transcriptome analysis revealed that the inclusion of CoCl2 supplements resulted in an enhanced influx of acetyl-CoA. • Proposed a mechanism for the accumulation of DTTAs for the role of ROS as a signal transduction pathway.