Biomass Conversion and Biorefinery

The widespread use of hexavalent chromium Cr(VI) in the leather industry causes substantial environmental problems when effluents are left untreated. Therefore, the present work attempts to assess the ability of Bacillus thuringiensis (V45) and Staphylococcus capitis (S21), isolated from tannery industry sediment, to detoxify Cr(VI) by reducing the oxidation state. Initially, the minimum tolerance of chromium by both bacteria was found up to 1000 μg/mL. V45 could tolerate Cr(VI) (520 μg/mL), and S21 could also tolerate hexavalent Cr(VI) (340 μg/mL). Similarly, both bacteria were able to tolerate other metals such as Hg2+ (40 μg/mL), Cu2+ (30 μg/mL), Ni2+ (60 μg/mL), Zn2+ (40 μg/mL), and Pb2+ (30 μg/mL). V45 and S21 could decrease Cr(VI) at a primary concentration of 50 μg/mL up to 86.42% and 97.34%, respectively. In optimization experiments, the best temperature to decrease Cr(VI) was shown to be 35 °C with pH 7 for 96 h. The occurrence of Cu2+ and Na+ slightly increased during the decrease of hexavalent Cr(VI) by V45, while the isolate S21 exhibited the same effects with Cu2+, Mn2+, and Na+. The carboxylate and amino conjugates in the biomass are intricate in the bioreduction of Cr(VI), as confirmed by FTIR spectroscopy. In addition, SEM imagery revealed the accumulation of Cr(VI) around both types of bacterial cells. The occurrence of other elements was evident from SEM-EDS spectroscopy. This study demonstrated the ability of native bacterial populations (V45 and S21) in tannery sediment to reduce Cr(VI) compounds.

Pythium oligandrum-derived biomass-activated carbon/graphene oxide (POC/GO) nanohybrid material is prepared for the first time by direct carbonization using the two-dimensional graphene oxide (GO)-incorporated Pythium oligandrum (PO). Note that the implanted GO is adsorbed and wrapped by the generated PO, which may be a feasible method to separate GO from aqueous systems. The obtained POC/GO exhibits special textural and high conductivity properties due to rapid electron transfer through the two-dimensional GO incorporated into carbonaceous network. Based on the functional POC/GO as a sensitizing substrate, the eosin Y dye-sensitized POC/GO@Pt photocatalysts show high-efficiency H2 evolution activity, which is 1.3 and 2.1 times higher than GO@Pt and POC@Pt. As well as the apparent quantum efficiency of POC/GO@Pt can reach to 32.2% at 430 nm. The superior catalytic activities for H2 evolution are attributed to the inner heat-treated GO which provided fast electron transport channels, while the outer POC with rich defect sites provided adsorption sites for the reactant H2O and co-catalyst Pt. Research ideas and design methods in this paper might provide a new way for preparing other biomass-based carbon materials and solar-driven high active photocatalyst.

Gần đây, biochar đã được thử nghiệm như một chất mang dinh dưỡng để tổng hợp phân bón giải phóng chậm. Tuy nhiên, loại phân bón giải phóng chậm này được thiết kế đặc biệt cho các loại đất có tính kiềm và nhiều canxi. Biochar có khả năng hấp thụ/kết hợp lượng lớn các ion dinh dưỡng nhờ vào diện tích bề mặt rộng, độ rỗng và các nhóm chức năng trên bề mặt. Thêm vào đó, các thuộc tính tự nhiên của biochar có thể được điều chỉnh để phù hợp với công dụng cụ thể. Do đó, trong nghiên cứu này, chúng tôi đã tập trung vào việc chế tạo một loại phân bón nitơ giải phóng chậm được thiết kế bằng cách biến đổi biochar thông qua quy trình loại tro để phù hợp với các loại đất có tính kiềm nhiều canxi, vì những loại đất này dễ bị mất nitơ nghiêm trọng. Biochar từ gỗ keo (Acacia Arabica L.) được sản xuất và loại tro bằng 0,1 M HCl. Sau đó, biochar thô và biochar đã loại tro được phân tích để đánh giá sự thay đổi về pH, CEC, hàm lượng tro, chất bay hơi, carbon cố định, diện tích bề mặt, thể tích lỗ, hình thái bề mặt, cấu trúc khoáng chất và các nhóm chức năng trên bề mặt sau khi loại tro. Phân bón nitơ giải phóng chậm dựa trên biochar (BSRNF) được tổng hợp bằng cách ngâm urea vào biochar, trong khi tinh bột và polyvinyl alcohol được sử dụng làm chất kết dính. Tác động của BSRNF đối với việc giải phóng N, bay hơi NH3, rửa trôi NO3 và phát thải N2O đã được nghiên cứu trên hai loại đất khác nhau so với urea thông thường. Kết quả cho thấy, việc loại tro đã thay đổi một cách đáng kể các thuộc tính của biochar, từ đó làm tăng khả năng hấp thụ urea vào biochar, điều này được xác nhận qua hình ảnh SEM, mẫu XRD và phổ FTIR của biochar thô và đã loại tro. Đánh giá BSRNF trên hai loại đất có tính kiềm nhiều canxi khác nhau cho thấy khả năng giải phóng N kéo dài lên đến ≥ 60 ngày. Do đó, BSRNF so với urea thông thường, đã giảm đáng kể lượng bay hơi NH3 lên đến 38,09%, rửa trôi NO3 lên đến 49,66% và phát thải N2O lên đến 52,39% của lượng N được bổ sung. BSRNF đã trì hoãn một cách đáng kể sự giải phóng nitơ trong đất, dẫn đến giảm thiểu tổn thất nitơ so với urea thông thường. Cơ chế này liên quan đến sự hấp thụ nitơ vào biochar, được cải thiện thêm bởi quá trình loại tro. Việc loại tro cũng đã khiến biochar trở nên phù hợp hơn cho các loại đất có tính kiềm nhiều canxi. Ngoài ra, tỷ lệ ứng dụng của biochar cũng đã tiết kiệm hơn.

Rice husk ash, an undervalued resource has a vast potential for the production of innovative materials. This research focuses on its twofold exploitation to a benign cum cost-effective catalytic material and silica, thereby paving a greener approach in the context of waste utilization. In the present study, engineered ash was prepared by activating rice husk ash. The engineered ash was functionalized via sulfonation and the efficacy of the developed catalyst was evaluated through esterification of hexadecanol. An experimental matrix was generated to investigate the effect of various process parameters onto the developed catalyst and determine the optimal conditions employing response surface methodology. An optimal value of temperature 189.3 °C, time 12 h and acid char ratio 5:1 was suggested for devising a high-performance catalyst having conversion and yield of 85.72% and 44.25% with a desirability of 0.994. Finally, the optimal catalyst was overlaid onto ceramic substrates to develop monoliths and explored for its efficacy as a stirrer in the esterification of hexadecanol. The developed catalyst can be used till five cycles revealing the strong adherence of the sulfonic groups. The physicochemical properties, textural characteristics and surface morphology of optimized catalyst were characterized by Fourier-transform infrared spectra, X-ray diffraction, field emission scanning electron microscope, X-ray fluorescence and thermogravimetric analysis. A consistent performance of engineered monoliths up to five cycles makes it one of the plausible alternatives to conventional catalysts at the industrial level. Simultaneously, silica of 84% yield with 96% purity extracted from rice husk ash embraces the concept of waste valorization.

Algae require optimal conditions for efficient photosynthesis. The present study investigates the effect of different growth conditions on the production of biomass, lipid, protein, total chlorophyll, and carotenoid. The findings show that the increase of light intensity from 80 to 280 μ mol/(m2.s) leads to higher specific growth rates (21.03/h). Also, total chlorophyll, lipid, and carotenoid content at the end of cultivation are the highest in the light intensity of 280 μ mol/(m2.s) due to higher biomass production (1.92 g/L). Under salinity stress, the specific growth rates (11.81/h) and the content of biomass (1.4 g/L), lipid, total chlorophyll, and carotenoid are slightly reduced compared to the control culture at the end of cultivation. This study also investigates the kinetics of chlorophyll and carotenoid extraction from mixed microalgae at different operating conditions with methanol solvent for the first time. The extraction results reveal that the highest kinetic constant and extraction efficiency of chlorophyll and carotenoid (94.10 and 95.43%, respectively) were achieved at 40 ˚C, pH 7, agitation of 300 rpm, and algal concentration of 4 g/L‏.

As a non-food, renewable energy resource, lignocellulosic biomass can be used for reducing greenhouse gas emissions. Hydrothermal carbonization (HTC) is a process to prepare the lignocellulosic biomass for subsequent thermochemical conversion. Biomass is reacted in hot compressed water at temperatures between 200 and 275 °C and at pressures sufficient to maintain liquid water. HTC was performed on corn stover, rice hulls, Tahoe mix (Jeffrey pine and white fir), switch grass, and Loblolly pine. These biomass sources encompass a variety of types, including a primary agricultural residue, a secondary agricultural residue, a forest product removed to reduce wildfires, a primary energy crop, and a primary forest crop. HTC reaction temperature was found to be the process variable with the greatest effect. For the five biomass studied, hydrochar mass yields were found to decrease with increasing reaction temperature, while higher heating values increased with increasing reaction temperature. Differences in these results among biomass sources were found to correlate with their original hemicellulose, lignin, aqueous soluble, and ash contents. These components appeared to be observable in scanning electron microscope images of hydrochar.

Based on previous studies on lactic acid (LA) production from food waste (FW, “cooked” waste from canteens and restaurants), the present study explored the feasibility of LA production from kitchen garbage (KG, “raw” waste from household kitchens). A considerable pretreatment method for fermentable sugar release in KG was investigated, and acid pretreatment was found to significantly promote polysaccharide hydrolysis. Furthermore, the optimal conditions of acid pretreatment were investigated through response surface methodology and determined to be 1.45% (w/v) sulfuric acid, 118.14 °C and 0.66 h, respectively, resulting in a polysaccharide conversion rate of 72.88%. Fourier transform infrared spectroscopy and X-ray diffraction revealed that the hemicellulose and lignin of KG were dissolved, which increased polysaccharide conversion in KG during acid pretreatment. Enterococcus mundtii was used in LA fermentation because it could metabolize a variety of fermentable sugars, including glucose, xylose, and fructose. Finally, the feasibility of LA production from KG hydrolysate with acid pretreatment was explored, and the maximum LA concentration and yield reached 60.3 g/L and 0.83 g/g total sugar, and 0.31 g/g KG (dry weight), respectively, which were 11% higher than those without acid pretreatment.

Currently, nanoemulsions (NEs) have been broadly applied for the target delivery and improved biological utilities of natural constituents. The present study aimed to prepare jojoba nanoemulsion (JOJ NE) and chitosan/jojoba nanoemulsion (CS/JOJ NE) by exploring the biological activities. JOJ NE and CS/JOJ NE have been successfully fabricated through an ultrasonic emulsification process. Zetasizer showed that the sizes of JOJ NE and CS/JOJ NE droplets are 76 ± 5 nm and 20 ± 3 nm, respectively. However, CS/JOJ NE showed a greater size with narrower PDI than the CS/JOJ NE owing to the presence of positively charged chitosan as shells incorporating the nanodroplets. Furthermore, surface charge results proved the high stability of the developed NE systems owing to the repulsive forces abundant within the systems. Finally, thermodynamic stability was investigated for 4 weeks, and the results confirmed the high stability of both emulsions. Various constituents were detected in jojoba oil via GC–MS analysis such as β-sitosterol, lupeol, and olean-12-en-3á-ol, acetate. CS/JOJ NE reflected more antibacterial activity than JOJ NE. For example, inhibition zones of B. subtilis and S. aureus were 31 mm and 20.67 mm using CS/JOJ NE and 24.67 mm and 17 mm using JOJ NE, respectively. MIC of CS/JOJ NE was 15.62 and 62.5 µg/mL, while MIC of JOJ NE was 125 and 500 µg/mL against B. subtilis and K. pneumoniae, respectively. MBC of CS/JOJ NE was 31.25 µg/mL for B. subtilis and 125 µg/mL for K. pneumoniae and C. albicans. Biofilm of B. subtilis was more sensitive followed by K. pneumoniae, S. aureus, and E. coli with an anti-biofilm percent of 94.42, 84.61, 84.66, and 88.64%, respectively, at CS/JOJ NE 75% of MBC. CS/JOJ NE was more effective than JOJ NE on the ultrastructure of tested bacteria. CS/JOJ NE exhibited α-amylase inhibitory with IC50 (133.8 µg/mL) less than JOJ NE (284.08 µg/mL).