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Lignocellulosic biomass has been widely considered as a renewable source for bioproducts and bioenergy production via various biorefinery techniques. Much effort has been taken for the valorization of carbohydrate compositions (cellulose and hemicellulose). Until recently, lignin has started to gain increasing attention as a renewable source that can be valorized to high-value products. It has unique advantages including low-cost, flexible modifiability, and wide compatibility that can be used for diverse purposes. The valorization of lignin into novel nanomaterials is a recent research endeavor that promises opportunities to increase the overall economy of conventional biorefineries, thus promoting the development of a circular bioeconomy, while its suitability for nanomaterial preparation and application is significantly related to its sources. To support the successful integration of conventional biorefineries and lignin nanomaterial preparation and utilization, this review first identify major biorefineries which produce lignin as byproducts, summarizes major preparation and applications of lignin, and then raises considerations and suggestions on the suitability of different lignin sources for nanomaterial preparation and application. Finally, some key challenges and perspectives are proposed for advancing the integration of lignin nanomaterials production and conventional biorefineries toward near-complete valorization of lignocellulosic biomass.

The characteristics of high-solids anaerobic digestion (AD) of sewage sludge were investigated by comparison with conventional low-solids processes. A series of batch experiments were conducted under mesophilic condition and the initial solid contents were controlled at four levels of 1.79%, 4.47%, 10.28% and 15.67%. During these experiments, biogas production, organic degradation and intermediate products were monitored. The results verified that high-solids batch AD of sewage sludge was feasible. Compared with the low-solids AD with solid contents of 1.79% or 4.47%, the high-solids processes decreased the specific biogas yield per gram of sludge volatile solids slightly, achieved the same organic degradation rate of about 40% within extended degradation time, but increased the volumetric biogas production rate and the treatment capability of digesters significantly. The blocked mass and energy transfer, the low substrate to inoculum rate and the excessive cumulative free ammonia were the main factors impacting the performance of high-solids batch AD.

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BACKGROUND: The potential effect of chromium on the denitrification process has drawn much attention recently. The efficient remediation of groundwater contaminated by both hexavalent chromate [Cr(VI)] and nitrate (NO 3 − ) was hampered due to the deficiency of denitrification in the presence of Cr(VI). The goal of this work was to understand the mechanisms of how Cr(VI) affected denitrification. RESULTS:To better understand the underlying nature, Cr(VI) effects on denitrification were investigated in batch. Negative effects of Cr(VI) exposure on denitrification were confirmed and ascribed to restriction of bacterial activities, by regulating functional genes expression and altering community composition. Stronger inhibition of the expression of denitrifying genes was observed with increased Cr(VI) loading (0-50 mg L −1 ). The critical inhibitory concentration and IC 50 of Cr(VI) on electron transport system activities were calculated to be 3.21 and 4.87 mg L −1 , respectively. Further amplicon analysis revealed that Betaproteobacteria were enriched, implying their potential key role in simultaneously removing nitrate and Cr(VI). The presence of Cr(VI) also upregulated the metabolic activities related to apoptosis. CONCLUSION: These findings shed light on the biogeochemical fates of Cr(VI) and NO 3− in aquifers, and may contribute in enhancing their practical application for bioremediation using microbial processes. ETSA assayElectron transport activity of the bacteria was measured by reducing 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyl tetrazolium wileyonlinelibrary.com/jctb

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