Vijay Singh

Process integration for simultaneous saccharification, fermentation, and recovery (SSFR): Production of butanol from corn stover using Clostridium beijerinckii P260

A simultaneous saccharification, fermentation, and recovery (SSFR) process was developed for the production of acetone-butanol-ethanol (AB or ABE), of which butanol is the main product, from corn stover employing Clostridium beijerinckii P260. Of the 86 g L(-1) corn stover provided, over 97% of the sugars were released during hydrolysis and these were fermented completely with an ABE productivity of 0.34 g L(-1)h(-1) and yield of 0.39. This productivity is higher than 0.31 g L(-1)h(-1) when using glucose as a substrate demonstrating that AB could be produced efficiently from lignocellulosic biomass. Acetic acid that was released from the biomass during pretreatment and hydrolysis was also used by the culture to produce AB. An average rate of generation of sugars during corn stover hydrolysis was 0.98 g L(-1)h(-1). In this system AB was recovered using vacuum, and as a result of this (simultaneous product recovery), 100% sugars were used by the culture.

Autohydrolysis of Miscanthus x giganteus for the production of xylooligosaccharides (XOS): kinetics, characterization and recovery.

The optima conditions of production and purification of xylooligosaccharides (XOS) from Miscanthus x giganteus (MxG) were investigated. Using autohydrolysis, XOS were produced at 160, 180 and 200°C at 60, 20 and 5min, respectively. XOS yield up to 13.5% (w/w) of initial biomass and 69.2% (w/w) of xylan were achieved. Results from HPAEC-PAD analysis revealed that X1-X9 sugar oligomers were produced. Higher temperature and longer reaction time resulted in lower product molecular weight. The three optimum conditions had similar degrees of polymerization XOS. Using 10% activated carbon (w/v) with ethanol/water elution recovered 47.9% (w/w) of XOS from pretreated liquid phase. The XOS could be fractionated by degree of polymerization according to ethanol concentration in the ethanol/water elution. Most of the XOS were washed out in 30% and 50% ethanol/water (v/v) fractions. Recoveries of 91.8% xylobiose, 86.9% xylotriose, 66.3% xylotetrose, 56.2% xylopentose and 48.9% xylohexaose were observed in XOS.

Ethanol production from food waste at high solids content with vacuum recovery technology.

Ethanol production from food wastes does not only solve environmental issues but also provides renewable biofuels. This study investigated the feasibility of producing ethanol from food wastes at high solids content (35%, w/w). A vacuum recovery system was developed and applied to remove ethanol from fermentation broth to reduce yeast ethanol inhibition. A high concentration of ethanol (144 g/L) was produced by the conventional fermentation of food waste without a vacuum recovery system. When the vacuum recovery is applied to the fermentation process, the ethanol concentration in the fermentation broth was controlled below 100 g/L, thus reducing yeast ethanol inhibition. At the end of the conventional fermentation, the residual glucose in the fermentation broth was 5.7 g/L, indicating incomplete utilization of glucose, while the vacuum fermentation allowed for complete utilization of glucose. The ethanol yield for the vacuum fermentation was found to be 358 g/kg of food waste (dry basis), higher than that for the conventional fermentation at 327 g/kg of food waste (dry basis).

Promise of combined hydrothermal/chemical and mechanical refining for pretreatment of woody and herbaceous biomass.

Production of advanced biofuels from woody and herbaceous feedstocks is moving into commercialization. Biomass needs to be pretreated to overcome the physicochemical properties of biomass that hinder enzyme accessibility, impeding the conversion of the plant cell walls to fermentable sugars. Pretreatment also remains one of the most costly unit operations in the process and among the most critical because it is the source of chemicals that inhibit enzymes and microorganisms and largely determines enzyme loading and sugar yields. Pretreatments are categorized into hydrothermal (aqueous)/chemical, physical, and biological pretreatments, and the mechanistic details of which are briefly outlined in this review. To leverage the synergistic effects of different pretreatment methods, conducting two or more pretreatments consecutively has gained attention. Especially, combining hydrothermal/chemical pretreatment and mechanical refining, a type of physical pretreatment, has the potential to be applied to an industrial plant. Here, the effects of the combined pretreatment (combined hydrothermal/chemical pretreatment and mechanical refining) on energy consumption, physical structure, sugar yields, and enzyme dosage are summarized.

Improvement of sugar yields from corn stover using sequential hot water pretreatment and disk milling.

Efficient pretreatment is essential for economic conversion of lignocellulosic feedstocks into monosaccharides for biofuel production. To realize high sugar yields with low inhibitor concentrations, hot water or dilute acid pretreatment followed by disk milling is proposed. Corn stover at 20% solids was pretreated with hot water at 160-200°C for 4-8min with and without subsequent milling. Hot water pretreatment and disk milling acted synergistically to improve glucose and xylose yields by 89% and 134%, respectively, compared to hot water pretreatment alone. Hot water pretreated (180°C for 4min) and milled samples had the highest glucose and xylose yields among all hot water pretreated and milled samples, which were comparable to samples pretreated with 0.55% dilute acid at 160°C for 4min. However, samples pretreated with 1% dilute acid at 150°C for 4min and disk milled had the highest observed glucose (87.3%) and xylose yields (83.4%).

Hybrid Variability and Effect of Growth Location on Corn Fiber Yields and Corn Fiber Oil Composition

ABSTRACT The variability in commercial corn hybrids for corn fiber yields, amounts of extractable oil, and levels of individual and total phytosterol components in corn fiber oil was determined. Also, the effect of growth location on fiber yields, fiber oil content, and the levels of individual and total phytosterol compounds was determined. Significant variation was observed in the commercial hybrids for fiber yield (13.2–16.6%) and fiber oil yield (0.9–2.4%). No significant correlation was observed between fiber and oil yields. Significant variations in the commercial corn hybrids were also observed in the individual phytosterol compounds in corn fiber oil: 2.9–9.2% for ferulate phytosterol esters (FPE); 1.9–4.3% for free phytosterols (St); and 6.5–9.5% for phytosterol fatty acyl esters (St:E). Positive correlations were observed among the three phytosterol compounds in the corn fiber oil (R = 0.75 for FPE and St:E; 0.48 for St:E and St; and 0.68 for FPE and St). The effect of location on dependent vari...

Pasting Properties and Surface Characteristics of Starch Obtained from an Enzymatic Corn Wet-Milling Process

ABSTRACT Recently, we reported the development of an enzymatic corn wet-milling process that reduces or eliminates sulfur dioxide requirements during steeping, considerably reduces steep time, and produces starch yields comparable to that of conventional corn wet-milling. The best results so far, using the enzymatic corn wet-milling procedure, were achieved when a particular protease enzyme (bromelain) was used. In this study, pasting properties and surface characteristics of starch obtained from six different enzyme treatments (three glycosidases [β-glucanase, cellulase, and xylanase] and three proteases [pepsin, acid protease, and bromelain]) using the enzymatic corn wet-milling procedure were evaluated and compared with those from starch obtained using the conventional corn wet-milling procedure. Significant effects from enzymatic milling were observed on all the three starch pasting properties (peak, shear thinning, and setback). The setback viscosities of starch from all enzyme treatments were signif...

Effect of Various Acids and Sulfites in Steep Solution on Yields and Composition of Corn Fiber and Corn Fiber Oil

ABSTRACT The addition of six acids (organic and inorganic) and four sulfite compounds (including gaseous SO2) during the conventional corn wet-milling steeping process of two yellow dent corn hybrids were evaluated for the effect on corn fiber yield, corn fiber oil yield, and the composition of three phytosterol compounds (ferulate phytosterol esters [FPE], free phytosterols [St], and phytosterol fatty acyl esters [St:E]) in the corn fiber oil. No significant effect of different sulfite compounds and acids were observed on corn fiber yields. However, a significant effect was observed on corn fiber oil yield and the composition of corn fiber oil for phytosterol compounds. Three of the sulfite compounds (including gaseous SO2) caused very little effect on the levels of phytosterol compounds compared with the control sample (corn steeped with sodium metabisulfite and lactic acid). However, for one hybrid, ammonium sulfite gave a significantly higher yield of FPE and St:E and had no effect on the yield of St....

A comparative study of anthocyanin distribution in purple and blue corn coproducts from three conventional fractionation processes

The aim was to compare the distribution of ANCs in purple and blue corn coproducts from three conventional corn fractionation processes and linking ANC partitioning in different coproducts to corn kernel phenotype. Total monomeric anthocyanin (TA) from purple corn extract was 4933.1±43.4mg cyanidin-3-glucoside equivalent per kg dry corn, 10 times more than blue corn. In dry milled purple corn, maximum ANCs were present in the pericarp (45.9% of total ANCs) and in wet-milling they were concentrated in steeping water (79.1% of total ANCs). For blue corn, the highest TA was in small grits and gluten slurry in dry-milling and wet-milling coproducts, respectively. HPLC showed the highest concentration of each ANC in steeping water for purple corn coproducts. Micrographs of kernel showed pigments concentrated in pericarp layer of purple but only in aleurone of blue corn. ANCs can concentrate in certain coproducts depending upon physical distribution of pigments in kernel.

Processing Method and Corn Cultivar Affected Anthocyanin Concentration from Dried Distillers Grains with Solubles

Anthocyanins are water-soluble pigments with health benefits and potential use as food colorants. The objectives of this work were to (1) determine optimum parameters for the extraction of anthocyanins from dried distillers grain with solubles (DDGS), (2) develop a method of anthocyanin extraction from DDGS, (3) quantify and identify the extracted anthocyanins, and (4) determine the effect of processing methods and corn cultivars on anthocyanin concentration. DDGS samples were prepared from purple (PC) and dark (DC) corn and processed using conventional enzymes (C) and granular starch hydrolyzing enzymes (GC). Three independent variables (ethanol concentration (0, 12.5, and 25%); liquid-to-solid ratio (30:1, 40:1, 50:1 mL/g); and extraction temperature (4, 22, and 40 °C)) and two dependent variables (anthocyanin concentration and a-value (redness)) were used. Results showed that dark corn DDGS gave anthocyanin concentration higher than that of purple corn. The GC process showed total anthocyanin concentration higher than that of the conventional method of DDGS production. The maximum anthocyanin concentration was obtained at 12.5% ethanol, 40:1 liquid-to-solid ratio, and 22 °C for C-PC [321.0 ± 37.3 μg cyanidin-3 glucoside (C3G) equivalent/g DDGS]. For GC-PC, 25% ethanol, 30:1 liquid-to-solid ratio, and 22 °C gave 741.4 ± 12.8 μg C3G equivalent/g DDGS. For GC-DC, 12.5% ethanol, 40:1 liquid-to-solid ratio, and 40 °C extraction gave 1573.4 ± 84.0 μg C3G equivalent/g DDGS. LC/MS-MS analysis showed that the major anthocyanins were cyanidin-3-glucoside, cyanidin-3-(6″-malonyl) glucoside, and peonidin-3-(6″malonyl) glucoside. In conclusion, anthocyanin extraction from colored corn DDGS can be optimized using 12.5% ethanol, 40:1 mL/g ratio, and 22 °C.