Soaking in aqueous ammonia (SAA) was investigated as a pretreatment method for corn stover. In this method, the feedstock was soaked in aqueous ammonia over an extended period (10–60 d) at room temperature. It was done without agitation at atmospheric pressure. SAA treatment removed 55–74% of the lignin, but retained nearly 100% of the glucan and 85% of the xylan. The xylan remaining in the corn stover after SAA treatment was hydrolyzed along with the glucan by xylanase present in the Spezyme CP enzyme. In the simultaneous saccharification and fermentation (SSF) test of SAA-treated corn stover, using S. cerevisiae (D5A), an ethanol yield of 73% of theoretical maximum was obtained on the basis of the glucan content in the treated corn stover. The accumulation of xylose in the SSF appears to inhibit the cellulase activity on glucan hydrolysis, which limits the yield of ethanol. In the simultaneous saccharification and co-fermentation (SSCF) test, using recombinant E. coli (KO11), both the glucan and xylose were effectively utilized, resulting in on overall ethanol yield of 77% based on the glucan and xylan content of the substrate. When the SSCF process is used, the fact that the xylan fraction is retained during pretreatment is a desirable feature since the overall bioconversion can be carried out in a single step without separate recovery of xylose from the pretreatment liquid.

Pretreatment of corn stover by soaking in aqueous ammonia.

Corn stover is usually treated by an energy-intensive or expensive process to extract sugars for bioenergy production. However, it is possible to directly generate electricity from corn stover in microbial fuel cells (MFCs) through the addition of microbial consortia specifically acclimated for biomass breakdown. A mixed culture that was developed to have a high saccharification rate with corn stover was added to single-chamber, air-cathode MFCs acclimated for power production using glucose. The MFC produced a maximum power of 331 mW/m2 with the bioaugmented mixed culture and corn stover, compared to 510 mW/m2 using glucose. Denaturing gradient gel electrophoresis (DGGE) showed the communities continued to evolve on both the anode and corn stover biomass over 60 days, with several bacteria identified including Rhodopseudomonas palustris. The use of residual solids from the steam exploded corn stover produced 8% more power (406 mW/m2) than the raw corn stover. These results show that it is possible to directly generate electricity from waste corn stover in MFCs through bioaugmentation using naturally occurring bacteria.

Bioaugmentation for electricity generation from corn stover biomass using microbial fuel cells.

It has been suggested that the ecological impact of crickets as a source of dietary protein is less than conventional forms of livestock due to their comparatively efficient feed conversion and ability to consume organic side-streams. This study measured the biomass output and feed conversion ratios of house crickets (Acheta domesticus) reared on diets that varied in quality, ranging from grain-based to highly cellulosic diets. The measurements were made at a much greater population scale and density than any previously reported in the scientific literature. The biomass accumulation was strongly influenced by the quality of the diet (p 99% mortality without reaching a harvestable size. Therefore, the potential for A. domesticus to sustainably supplement the global protein supply, beyond what is currently produced via grain-fed chickens, will depend on capturing regionally scalable organic side-streams of relatively high-quality that are not currently being used for livestock production.

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Crickets are not a free lunch: protein capture from scalable organic side-streams via high-density populations of Acheta domesticus.

Alkali treatment of corn stover improves the availability of cellulose and hemicellulose for enzymatic attack. Treatments were carried out for 1 to 60 min at temperatures and NaOH concentrations ranging from 100 to 150 degrees C and 0 to 2%, respectively. Solubilization of the stover and sugar production by enzymatic hydrolysis (Trichoderma viride cellulase) of the solid residue and the dissolved solids were used to measure the effect of caustic treatment. At 150 degrees C and 2% NaOH concentration, 65% of the original stover was dissolved after 5 min and 52% saccharification (g sugar/g stover) of the residue and dissolved solids by enzymatic hydrolysis was achieved compared to 20% for untreated corn stover. (6 Refs.)

Alkali treatment of corn stover to improve sugar production by enzymatic hydrolysis

A comparison of alkali treatment methods to improve the nutritive value of straw. i. digestibility and metabolizability

Alkali Treatments of Corn Stover to Increase Nutritive Value

Effects of urea and aqueous ammonia treatment on the composition and nutritive value of maize residues

Nutritive value of thermoammoniated and steam-treated maize stover. I. Intake, digestibility and nitrogen retention.

Fodder and tuber yields, and fodder quality of sweet potato cultivars at different maturity stages in the West African humid forest and savanna zones

Corn stover, ground through a 16-cm screen, was steam-processed at 162 kg/cm2 and 205 °C for 15 min Control and treated stover were evaluated for intake and digestibility of organic constituents with eight wether lambs in a single crossover design Prior to feeding, water was added to control corn stover to approximate the moisture content of treated stover and to reduce dustiness Soybean meal was added to both rations and, in addition, urea was added to treated stover to attempt to make up for nitrogen rendered unavailable by treatment Steam treatment increased (P < 005) ADF, ADIN, permanganate lignin and acetic acid Dry matter intake increased (P < 005) by 55% with steam treatment Treatment also increased (P < 005) apparent digestibilities of organic matter, energy, non cell wall contents and cellulose but decreased (P < 005) digestibilities of NDF and ADF The extent of improvement in energy digestibility was limited by heat damage due to processing Modifications in treatment conditions sho

U. I. Oji

Papers

Alkali Treatments of Corn Stover to Increase Nutritive Value

Effects of urea and aqueous ammonia treatment on the composition and nutritive value of maize residues

Nutritive value of thermoammoniated and steam-treated maize stover. I. Intake, digestibility and nitrogen retention.

Fodder and tuber yields, and fodder quality of sweet potato cultivars at different maturity stages in the West African humid forest and savanna zones

Nutritive value of steam-treated corn stover