Mechanistic investigations in ultrasound-assisted biodegradation of phenanthrene

Ultrasonic Disintegration to Improve Anaerobic Digestion of Microalgae with Hard Cell Walls-Scenedesmus sp. and Pinnularia sp

Microalgae are considered to be very promising feedstocks for biomethane production. It has been shown that the structure of microalgal cell walls can be highly detrimental to the anaerobic digestibility of biomass. Therefore, there is a real need to seek ways to eliminate this problem. The aim of the present study was to assess the effect of ultrasonic disintegration of Scenedesmus sp. and Pinnularia sp. microalgal biomass on the performance and energy efficiency of anaerobic digestion. The pretreatment was successful in significantly increasing dissolved COD and TOC in the system. The highest CH₄ yields were noted for Scenedesmus sp. sonicated for 150 s and 200 s, which produced 309 ± 13 cm³/gVS and 313 ± 15 cm³/gVS, respectively. The 50 s group performed the best in terms of net energy efficiency at 1.909 ± 0.20 Wh/gVS. Considerably poorer performance was noted for Pinnularia sp., with biomass yields and net energy gains peaking at CH₄ 250 ± 21 cm³/gVS and 0.943 ± 0.22 Wh/gVS, respectively. Notably, the latter value was inferior to even the non-pretreated biomass (which generated 1.394 ± 0.19 Wh/gVS).

Ultrasonic stimulation of milk fermentation: effects on degradation of pesticides and physiochemical, antioxidant, and flavor properties of yogurt

BACKGROUND

Ultrasound has the potential to increase microbial metabolic activity, so this study explored the stimulatory effect of ultrasound pre-treatment on the degradation of four common pesticides (fenitrothion, chlorpyrifos, profenofos, and dimethoate) during milk fermentation by Lactobacillus plantarum and its effect on yogurt quality.

RESULTS

Appropriate ultrasound pretreatment significantly enhanced the growth of L. plantarum. The degradation percentages of pesticides increased by 19-38% under ultrasound treatment. Ultrasonic intensity, pulse duty cycle, and duration time were key factors affecting microbial growth and pesticide degradation. Under optimal ultrasonic pre-treatment conditions, the degradation rate constants of four pesticides were at least 3.4 times higher than those without sonication. In addition, such ultrasound pretreatment significantly shortened yogurt fermentation time, increased the water holding capacity, hardness and antioxidant activity of the yogurt, and improved the flavor quality of the yogurt.

CONCLUSION

Ultrasonic pretreatment significantly accelerated the degradation of the four pesticides during yogurt fermentation. In addition, such ultrasound pretreatment increased the efficiency of yogurt making and improved the quality of yogurt in terms of water holding capacity, firmness, antioxidant activity, and flavor. These findings provide a basis for the application of ultrasound to the removal of pesticide residues and quality improvement of yogurt. © 2022 Society of Chemical Industry.

Enhancing Biomethane Production From Lignite by an Anaerobic Polycyclic Aromatic Hydrocarbon Degrading Fungal Flora Enriched From Produced Water

The coal-degrading ability of microorganisms is essential for the formation of biogenic coalbed methane. The ability to degrade the aromatic compound of coal is more important because it is perceived as the main refractory component for bioconversion. In this paper, a polycyclic aromatic hydrocarbon (PAH) degrading fungal community (PF) was enriched from produced water using phenanthrene as sole carbon source. The goal was to improve both the microbial structure of the methanogenic microflora and its coal-degrading ability. Two strategies were pursued. The first used coal pretreatment with PF (PP), followed by methane production by methanogenic microflora; the second used methane production directly from coal by mixed culture of PF and methanogenic microflora (PM). The results showed that methane productions of PP and PM increased by 29.40 and 39.52%, respectively. After 7 days of cultivation, the fungal community has been altered in PP and PM, especially for Penicillium the proportions of which were 67.37 and 89.81% higher than that in methanogenic microflora, respectively. Furthermore, volatile fatty acid accumulations increased by 64.21 and 58.15%, respectively. The ¹³C-NMR results showed that PF addition promoted the transformation of aromatic carbons in coal to carboxyl and carbonyl carbons, which contributed greatly to the production of methane together with oxygen-containing functional groups. These results suggest that methane production can be increased by indigenous PAH-degrading fungi by improving the fermentation of aromatics in coal and the generation of volatile fatty acids. This provided a feasible method for enhancing biomethane generation in the coal seam.