Effect of ensilage on bioconversion of switchgrass to ethanol based on liquid hot water pretreatment / 生物工程学报

Ensilage is a traditional way of preserving fresh biomass. However, in order to apply ensilage to the ethanol biorefinery, two parameters need to be evaluated: quantity and quality changes of the biomass; and its effects on bioconversion process. To study these two aspects, switchgrass harvested on three different time points (Early, mid and late fall) were used as feedstock. The early fall harvested biomass was ensiled at 5 moisture levels ranging from 30% to 70%. Silage of 40% moisture and 3 other raw switchgrass were pretreated with liquid hot water, followed by enzymatic hydrolysis as well as simultaneous saccharification and fermentation. After 21 days storage pH values of all silages decreased below 4.0 and the dry matter losses were less than 2.0%, and structural sugars contents did not change dramatically. Liquid hot water caused more hemicellulose dissolution in the silage than in unensiled switchgrass. However, ensilage also increased the risk of releasing more sugar degradation products; After enzymatic hydrolysis, silage obtained higher total glucose, xylose and galactose yields than raw materials; After simultaneous saccharification and fermentation, ethanol concentration in silage was 12.1 g/L, higher than the unensiled switchgrass (10.3 g/L, 9.7 g/L and 10.6 g/L for early, mid and late fall respectively). Our results suggest that ensilage helps increase pretreatment efficiency and sugar yield, which increases final ethanol production.

Effects of Fertilization and Irrigation on Establishment and Growth of Switchgrass (Panicum virgatum L.) in Sokoto, Nigeria.

Aims: To determine the effects of fertilization and irrigation on establishment and growth of switchgrass (Panicum virgatum L.) in Sokoto, Nigeria and its adaptability. Study Design: A factorial experiment laid down in split – plot design. Place and Duration of Study: The study was carried out during 2008/2009 and 2009/2010 dry seasons in upland and lowland areas in Sokoto, Nigeria. Methodology: The effects of nitrogen fertilizer, manure and irrigation interval on percentage plant establishment, plant height, number of leaves and stem diameter of P. virgatum were assessed. Four levels of nitrogen (0, 25, 50 and 75 kg N ha-1), three rates of manure (0, 5 and 10 t ha-1) and three irrigation regimes (w2, w4 and w6). Results: Results indicate that there is no significant (P = 0.05) increase in percentage plant establishment, plant height, number of leaves and stem diameter by raising nitrogen rate from 50 to 75 kg N ha-1, manure rate from 5 – 10 t ha-1 or irrigation intervals from w2 to w4 days. The findings of the study revealed that a combination of 50 kg N ha-1, with 5 t ha-1 of manure and w2 irrigation interval enhanced percentage plant establishment, plant height, number of leaves and stem diameter.