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In this study, the target was the generation of fermentable monosaccharides from hardwoods that can be converted into value-added chemicals, such as polyhydroxybutyrates (PHB). Poplar flour was subjected to a hot-water pretreatment. The pretreatment conditions were optimized using a response surface methodology (RSM) on a 2 3 full central composites design by varying temperature, reaction time and solid loading. The optimal pretreatment condition for producing sugars was 200 °C, 22 min and 20% solid loading. After pretreatment the solid residue was treated with a commercial cellulase/xylanase preparation and released sugars quantified. The total sugars yield was applied as response variable to the RSM. A maximum yield of 96% sugars was obtained. Potential fermentation inhibitors were also detected at low concentrations (acetic acid, furfural, hydroxymethylfurfural). A preliminary trial using wood hydrolysates in a fed-batch bioreactor using a mixed microbial consortia afforded PHB (14% on biomass basis) and maximum PHB productivity of 0.18 g/L/h. [ABSTRACT FROM AUTHOR]

Potato peel waste (PPW) as zero value byproduct generated from food processing plant contains a large quantity of starch, non-starch polysaccharide, lignin, protein, and lipid. PPW as one promising carbon source can be managed and utilized to value added bioproducts through a simple fermentation process using undefined mixed cultures inoculated from wastewater treatment plant sludge. A series of non-pH controlled batch fermentations under different conditions such as pretreatment process, enzymatic hydrolysis, temperature, and solids loading were studied. Lactic acid (LA) was the major product, followed by acetic acid (AA) and ethanol under fermentation conditions without the presence of added hydrolytic enzymes. The maximum yields of LA, AA, and ethanol were respectively, 0.22 g g −1 , 0.06 g g −1 , and 0.05 g g −1 . The highest LA concentration of 14.7 g L −1 was obtained from a bioreactor with initial solids loading of 60 g L −1 at 35 °C. [ABSTRACT FROM AUTHOR]

Polyhydroxybutyrate (PHB) is one of most biodegradable bioplastic, but its high cost and brittleness limits its applications. In this study, low-value waste byproduct from a fermentation process of potato peel waste, called the potato peel waste fermentation residue (PPW-FR) fibers, were recovered and compounded with PHB to form biocomposites of tunable properties. The mechanical and thermal properties of pure PHB and biocomposites were investigated by thermogravimetric analysis (TGA), tensile and flexural tests, and dynamic mechanical analysis (DMA). Fiber content was shown to have a significant effect on the surface hydrophobicity and water absorption of the biocomposites. All absolute and specific mechanical properties and water absorption (by normalizing the measured parameters against the measured density ( ρ )) were investigated. The biodegradability of PHB and biocomposites were evaluated in soil over 8 months. The surface morphology, chemistry and melting/crystallization behavior were monitored and characterized by microscopy, FTIR spectroscopy and differential scanning calorimetry (DSC), respectively. The biocomposites showed poor mechanical properties but extremely higher biodegradation rate as compared with pure PHB, especially when the fiber content was >15%. The degradation rate increased with increasing fiber content and positively correlated to the water absorption showing more cracks and deeper pits. FTIR spectroscopic analysis showed that the plant polysaccharides and PHB within the biocomposite were degraded with exposure time. At 50% fiber content the biocomposites were completely degraded by 8 months. These PPW-FR based biocomposites offer new opportunities for fast degrading biomaterials in agricultural and horticultural applications. [ABSTRACT FROM AUTHOR]

Efficient conversion of all components in lignocellulosic biomass is essential to realizing economic feasibility of biorefineries. However, lignin cannot be fermented using biochemical routes. Furthermore, high lignin and high ash residues from simultaneous saccharification and fermentation (SSF) is difficult to thermochemically process due to feed line plugging and bed agglomeration. In this study a corn stover SSF digester residue was thermally pretreated at 300 °C for 22.5 min and gasified in a fluidized bed gasifier to study the effect of thermal pretreatment on its processing behavior. Untreated, pelletized SSF residue was gasified at the same conditions to establish the baseline processing behavior. Results indicate the thermal pretreatment process removes a substantial portion of the polar and non-polar extractives, with a resultant increase in the concentration of lignin, cellulose, and ash. Feed line plugging was not observed, although bed agglomeration occurred at similar rates for both feedstocks, suggesting that overall ash content is the most important factor affecting bed agglomeration. Benzene, phenol, and polyaromatic hydrocarbons in the tar were present at higher concentrations in the treated material, with higher tar loading in the product gas. Total product gas generation is lower for the treated material, although overall gas composition does not change. [ABSTRACT FROM AUTHOR]

Mixed cultures fermentation can be used to convert organic wastes into various chemicals and fuels. This study examined the fermentation performance of four batch reactors fed with different agricultural (orange, banana, and potato (mechanical and steam)) peel wastes using mixed cultures, and monitored the interval variation of reactor microbial communities with 16S rRNA genes using Illumina sequencing. All four reactors produced similar chemical profile with lactic acid (LA) as dominant compound. Acetic acid and ethanol were also observed with small fractions. The Illumina sequencing results revealed the diversity of microbial community decreased during fermentation and a community of largely lactic acid producing bacteria dominated by species of Lactobacillus developed. [ABSTRACT FROM AUTHOR]

Three undefined mixed cultures (activated sludge) from different municipal wastewater treatment plants were used as seeds in a novel lactic acid fermentation process fed with potato peel waste (PPW). Anaerobic sequencing batch fermenters were run under identical conditions to produce predominantly lactic acid. Illumina sequencing was used to examine the 16S rRNA genes of bacteria in the three seeds and fermenters. Results showed that the structure of microbial communities of three seeds were different. All three fermentation products had unique community structures that were dominated (>96%) by species of the genus Lactobacillus , while members of this genus constituted <0.1% in seeds. The species of Lactobacillus sp. differed among the three fermentations. Results of this study suggest the structure of microbial communities in lactic acid fermentation of PPW with undefined mixed cultures were robust and resilient, which provided engineering prospects for the microbial utilization of carbohydrate wastes to produce lactic acid. [ABSTRACT FROM AUTHOR]