No abstract

No abstract

Lignin component in lignocellulosic biomass always adversely affects the efficiency of its enzymatic saccharification and subsequent bioethanol production. To mitigate the lignin inhibition, this work thoroughly evaluated the effectiveness of deacetylation and steam pretreatment for improved fermentable sugars and bioethanol production from hardwood as well as quantified the relative contribution of lignin toward physical blockage effect and unproductive adsorption effect on cellulose hydrolysis. It was found that deacetylation reduced the formation of acid catalyst, thus significantly mitigating lignin inhibition on cellulose hydrolysis. The addition of Na2S in deacetylation was more liable in improving biomass porosity, and the addition of Na2SO3 was more favorable for removing surface lignin; both of these factors contributed to the decreased physical blockage effect of lignin. Besides, X-ray photoelectron spectroscopy (XPS) results indicated that deacetylation distinctly suppressed the undesirable lignin repolymerization and the formation of phenolic hydroxyl groups, which could alleviate the unproductive adsorption effect of lignin. When lignin was isolated from the deacetylation–steam-pretreated substrates and added to the enzymatic hydrolysis of Avicel, a distinctly lower lignin inhibition was observed compared to the samples without deacetylation. Besides, the lignin inhibition showed a strong correlation with the extent of lignin repolymerization, proving the lignin inhibition mitigating effect of deacetylation through modification of the lignin structure.

No abstract

Abstract. Temperature sensitivity of soil organic carbon (SOC) mineralization (i.e., Q 10 ) determines how strong the feedback from global warming may be on the atmospheric CO 2 concentration; thus, understanding the factors influencing the interannual variation in Q 10 is important for accurately estimating local soil carbon cycle. In situ SOC mineralization rate was measured using an automated CO 2 flux system (Li-8100) in long-term bare fallow soil in the Loess Plateau (35 • 12 N, 107 • 40 E) in Changwu, Shaanxi, China from 2008 to 2013. The results showed that the annual cumulative SOC mineralization ranged from 226 to 298 g C m −2 yr −1 , with a mean of 253 g C m −2 yr −1 and a coefficient of variation (CV) of 13 %, annual Q 10 ranged from 1.48 to 1.94, with a mean of 1.70 and a CV of 10 %, and annual soil moisture content ranged from 38.6 to 50.7 % soil water-filled pore space (WFPS), with a mean of 43.8 % WFPS and a CV of 11 %, which were mainly affected by the frequency and distribution of precipitation. Annual Q 10 showed a quadratic correlation with annual mean soil moisture content. In conclusion, understanding of the relationships between interannual variation in Q 10 , soil moisture, and precipitation are important to accurately estimate the local carbon cycle, especially under the changing climate.