Surfactant-enhanced anaerobic acidogenesis of Canna indica L. by rumen cultures

Polyoxyethylene sorbitan monoolate (Tween 80) was used to enhance the anaerobic acidogenesis of Canna indica L. (canna) by rumen culture in this study. Dose of Tween 80 at 1 ml/l enhanced the volatile fatty acids (VFA) production from the acidogenesis of canna compared to the control. However, Tween 80 at higher dosages than 5 ml/l inhibited the rumen microbial activity and reduced the VFA yield. Response surface methodology was successfully used to optimize the VFA yield. A maximum of VFA yield of 0.147 g/g total solids (TS) added was obtained at canna and Tween 80 concentrations of 6.3g TS/l and 2.0 ml/l, respectively. Dosage of Tween 80 at 1-3.75 ml/l reduced the unproductive adsorption of microbes or enzymes on the lignin part in canna and increased microbial activity. A high VFA production was achieved from canna presoaked with Tween 80, suggesting that the structure of canna was disrupted by Tween 80.     

Pretreatment of switchgrass for sugar production with the combination of sodium hydroxide and lime

Sodium hydroxide (NaOH) and lime (Ca(OH)₂) were innovatively used together in this study to improve the cost-effectiveness of alkaline pretreatment of switchgrass at ambient temperature. Based on the sugar production in enzymatic hydrolysis, the best pretreatment conditions were determined as: residence time of 6 h, NaOH loading of 0.10 g/g raw biomass, NaOH addition at the beginning, Ca(OH)₂ loading of 0.02 g/g raw biomass, and biomass wash intensity of 100 ml water/g raw biomass, at which the glucose and xylose yields were respectively 59.4% and 57.3% of the theoretical yields. The sugar yield of the biomass pretreated using the combination of 0.10 g NaOH/g raw biomass and 0.02 g Ca(OH)₂/g raw biomass was found comparable with that of the biomass pretreated using 0.20 g NaOH/g raw biomass at the same conditions, while the chemical expense was remarkably reduced due to the low cost of lime and the reduced loading of NaOH.     

Design of acidogenic reactors for the anaerobic treatment of the organic fraction of solid food waste

Volatile Fatty Acids (VFA) production by anaerobic fermentation of organic solid wastes was studied at laboratory scale. The influence of initial substrate concentration was evaluated on VFA production. Completely mixed reactors (0.9?l) were used at mesophilic temperature (35?°C). Food wastes had 43.8% Total Solids content. Three dilutions of substrate (1/25, 1/10 and 1/5) corresponding to 1.75%, 4.38% and 8.76% of Total Solids and five values of Organic Loading Rates: 2, 5, 10, 12.5 and 25?kg COD/m³?d were studied. It was found that substrate 1/10 led to 14?g VFA/l at a loading rate of 12.5?kg COD/m³?d and an hydraulic retention time of 3.7 d. The main VFA produced were especially acetate and butyrate. Substrate diluted 1/5 led to 26.1?g VFA/l at a loading of 5?kg COD/m³?d and an hydraulic retention time of 15.1 d, but biomass production was not optimal. In a second study, a cascade of three reactors was used. An effluent with 42?g VFA/l was obtained at steady-state conditions at a loading of 12.5?kg of COD/m³?d and an hydraulic retention time of 12.5?d. The distribution of VFA was the following: 36% of propionate, 34% of acetate and 22.5% of butyrate.     

Effect of Lime Pretreatment on Granulation of Switchgrass

Densification of switchgrass into consistent and high-density solid feedstock will reduce the cost of transport, handling, and storage to produce fuels and chemicals. Development a novel, low-cost densification technology is critical for reducing the delivered cost of feedstock while improving the bulk flow properties of densified products. In this paper, a novel wet granulation technology was proposed to investigate the effect of lime pretreatment on the production of switchgrass granules. Granulation is a process of agglomerating fine powders by wetting powder surfaces with liquid binders and mild application of shear/vibrating forces. Switchgrass was size reduced into fine powders using a knife mill and pretreated with three lime loading rates (0.05, 0.1, 0.2 g/g of biomass) at 121 °C for 30 min and at room temperature (25 °C) for 72 h. The structural modification of pretreated samples was analyzed by scanning electron microscopy and autofluorescence microscopy. Pretreated samples were granulated using a pan granulator with pre-formulated starch binder. Granules made from 20 % (0.2 g/g of biomass) lime loading rate had significantly higher single granule density and angle of repose with lower binder requirement than that of untreated granules. Lime treatment did not significantly increase the bulk density and hardness of granules. Lime-treated granules had significantly higher ash content and lower gross calorific value than that of untreated granules. In overall, lime treatment was not attractive to produce granules for thermochemical conversion platform, but lime-treated granules could be used to produce liquid biofuels and platform chemicals in biochemical conversion platform.     

Effect of structural features on enzyme digestibility of corn stover

Corn stover was pretreated with excess calcium hydroxide (0.5 g Ca(OH)2/g raw biomass) in non-oxidative and oxidative conditions at 25, 35, 45, and 55 degrees C. The enzymatic digestibility of lime-treated corn stover was affected by the change of structural features (acetylation, lignification, and crystallization) resulting from the treatment. Extensive delignification required oxidative treatment and additional consumption of lime (up to 0.17 g Ca(OH)2/g biomass). Deacetylation reached a plateau within 1 week and there were no significant differences between non-oxidative and oxidative conditions at 55 degrees C; both conditions removed approximately 90% of the acetyl groups in 1 week at all temperatures studied. Delignification highly depended on temperature and the presence of oxygen. Lignin and hemicellulose were selectively removed (or solubilized), but cellulose was not affected by lime pretreatment in mild temperatures (25-55 degrees C), even though corn stover was contacted with alkali for a long time, 16 weeks. The degree of crystallinity slightly increased from 43% to 60% with delignification because amorphous components (lignin, hemicellulose) were removed. However, the increased crystallinity did not negatively affect the 3-d sugar yield of enzymatic hydrolysis. Oxidative lime pretreatment lowered the acetyl and lignin contents to obtain high digestibility, regardless of crystallinity. The non-linear models for 3-d hydrolysis yields of glucan (Y(g)), xylan (Y(x)), and holocellulose (Y(gx)) were empirically established as a function of the residual lignin (L) for the corn stover pretreated with lime and air.     

Effect of nickel oxide nanoparticles on bioethanol production: Process optimization,kinetic and metabolic studies

The present study optimized ethanol yield using nickel oxide (NiO) nanoparticles (NPs) as a biocatalyst. Additionally, Saccharomyces cerevisiae BY4743 cell growth and the bioethanol production kinetics were assessed. The Response Surface Methodology (RSM) model showed a coefficient of determination (R²) value of 0.93. The optimized process gave a biomass concentration and ethanol yield of 2.04 g/L and 0.26 g/g (1.03 and 1.19-fold increment compared to the control experiment), respectively. The process kinetic data showed that the inclusion of NiO NPs improved the affinity of S. cerevisiae BY4743 to glucose consumption, carbohydrate and protein accumulation. A significant reduction in volatile fatty acid (VFA) was observed in the presence of NiO NPs. The application of nano biocatalyst in simultaneous saccharification and fermentation of potato peel waste, meaningfully enhanced bioethanol production (>65 %). The study provided major insights into the use of NiO NPs to enhance the bioprocess of ethanol production.     

Application of response surface methodology for optimization of acidogenesis of cattail by rumen cultures

Acidogenesis of cattail using rumen cultures was carried out to produce volatile fatty acids (VFA) in this study. The influences of pH and substrate concentration on cattail degradation, VFA yield and microbial growth were investigated by using response surface methodology (RSM). Experimental results showed that a low substrate concentration and pH of 6.9 were optimal for acidogenesis of cattail. The highest cattail degradation efficiency, VFA yield and microbial yield were 75.9%, 0.41 g/g VS and 0.110 g/g VS, respectively. Further experiments confirmed that the main VFA in the acidogenesis of cattail were acetate, propionate and butyrate, while i-butyrate, valerate and i-valerate were also produced at low levels. The results suggested that acidogenesis using rumen cultures is a promising method for cattail disposal.     

Medium chain length polyhydroxyalkanoate (mcl-PHA) production from volatile fatty acids derived from the anaerobic digestion of grass

A two step biological process for the conversion of grass biomass to the biodegradable polymer medium chain length polyhydroxyalkanoate (mcl-PHA) was achieved through the use of anaerobic and aerobic microbial processes. Anaerobic digestion (mixed culture) of ensiled grass was achieved with a recirculated leach bed bioreactor resulting in the production of a leachate, containing 15.3 g/l of volatile fatty acids (VFAs) ranging from acetic to valeric acid with butyric acid predominating (12.8 g/l). The VFA mixture was concentrated to 732.5 g/l with a 93.3 % yield of butyric acid (643.9 g/l). Three individual Pseudomonas putida strains, KT2440, CA-3 and GO16 (single pure cultures), differed in their ability to grow and accumulate PHA from VFAs. P. putida CA-3 achieved the highest biomass and PHA on average with individual fatty acids, exhibited the greatest tolerance to higher concentrations of butyric acid (up to 40 mM) compared to the other strains and exhibited a maximum growth rate (μ_MAX?=?0.45 h^?1). Based on these observations P. putida CA-3 was chosen as the test strain with the concentrated VFA mixture derived from the AD leachate. P. putida CA-3 achieved 1.56 g of biomass/l and accumulated 39 % of the cell dry weight as PHA (nitrogen limitation) in shake flasks. The PHA was composed predominantly of 3-hydroxydecanoic acid (>65 mol%).     

Enhanced methane production in a two-phase anaerobic digestion plant, after CO2 capture and addition to organic wastes

Cost-effective technologies are needed to reach the international greenhouse gas (GHG) reduction targets in many fields, including waste and biomass treatment. This work reports the effects of CO₂ capture from a combustion flue gas and its use in a newly-patented, two-phase anaerobic digestion (TPAD) process, to improve energy recovery and to reduce CO₂ emissions. A TPAD process, fed with urban wastewater sludge, was successfully established and maintained for several months at pilot scale. The TPAD process with injection of CO₂ exhibits efficient biomass degradation (58% VSS reduction), increased VFA production during the acidogenic phase (leading to VFA concentration of 8.4 g/L) and high biomethane production (0.350 Sm³/kg_SSV; 0.363 Sm³/m³_react·d). Moreover, CO₂ intake in the acid phase has a positive impact on the overall GHG balance associated to biomethane production, and suggests an improved solution for both emission reduction and biomass conversion into biomethane.     

Ethanol recovery from corn fiber hydrolysate fermentations by pervaporation

Corn fiber, a byproduct of corn wet milling, is an attractive feedstock for biomass ethanol production. Corn fiber was hydrolyzed by dilute sulfuric acid and neutralized by one of two methods: conventional lime treatment or neutralization by strongly basic anion exchange. The anion exchange neutralized (AEN) hydrolysate contained substantially lower levels of the inhibiting compounds furfural, 5-hydroxymethylfurfural, and acetic acid compared to the lime neutralized hydrolysate. In batch fermentations the ethanol yields and final ethanol concentration of the two hydrolysates were similar at 0.32-0.43 g/g and 29-44 g/l, respectively. Sugar consumption in the AEN fermentations was superior. Coupling of a membrane pervaporation unit to a fed-batch fermentation of AEN hydrolysate maintained the ethanol concentration below 25 g/l with complete sugar utilization for approximately 5 days. A concentrated ethanol stream of 17 wt.% ethanol was produced by the pervaporation unit.     

Optimization of exopolysaccharide overproduction by Lactobacillus confusus in solid state fermentation under high salinity stress

It is believed that high concentrations of sodium chloride (NaCl) suppress the biosynthesis of exopolysaccharide (EPS) in lactic acid bacteria (LAB). Nevertheless, overproduction of EPSs due to high salinity stress in solid state fermentation performed on an agar surface was demonstrated in this study using a response surface methodology via a central composite design (CCD). Under optimized conditions with NaCl 4.97% and sucrose 136.5 g/L at 40.79 h of incubation, the EPS yield was 259% (86.36 g/L of EPS), higher than the maximum yield produced with the modified MRS medium containing only 120 g/L of sucrose without NaCl (33.4 g/L of EPS). Biosynthesis of EPS by Lactobacillus confusus TISTR 1498 was independent of biomass production. Our results indicated that high salinity stress can enhance EPS production in solid state fermentation.     

Short‐term lime pretreatment of poplar wood

Short‐term lime pretreatment uses lime and high‐pressure oxygen to significantly increase the digestibility of poplar wood. When the treated poplar wood was enzymatically hydrolyzed, glucan and xylan were converted to glucose and xylose, respectively. To calculate product yields from raw biomass, these sugars were expressed as equivalent glucan and xylan. To recommend pretreatment conditions, the single criterion was the maximum overall glucan and xylan yields using a cellulase loading of 15 FPU/g glucan in raw biomass. On this basis, the recommended conditions for short‐term lime pretreatment of poplar wood follow: (1) 2 h, 140°C, 21.7 bar absolute and (2) 2 h, 160°C, and 14.8 bar absolute. In these two cases, the reactivity was nearly identical, thus the selected condition depends on the economic trade off between pressure and temperature. Considering glucose and xylose and their oligomers produced during 72 h of enzymatic hydrolysis, the overall yields attained under these recommended conditions follow: (1) 95.5 g glucan/100 g of glucan in raw biomass and 73.1 g xylan/100 g xylan in raw biomass and (2) 94.2 g glucan/100 g glucan in raw biomass and 73.2 g xylan/100 g xylan in raw biomass. The yields improved by increasing the enzyme loading. An optimal enzyme cocktail was identified as 67% cellulase, 12% β‐glucosidase, and 24% xylanase (mass of protein basis) with cellulase activity of 15 FPU/g glucan in raw biomass and total enzyme loading of 51 mg protein/g glucan in raw biomass. Ball milling the lime‐treated poplar wood allowed for 100% conversion of glucan in 120 h with a cellulase loading of only 10 FPU/g glucan in raw biomass. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

Mesophilic anaerobic treatment of sludge from saline fish farm effluents with biogas production

The mesophilic anaerobic treatment of sludge from saline fish farm effluents (total solids (TS): 8.2-10.2 wt%, chemical oxygen demand (COD): 60-74 g/l, sodium (Na): 10-10.5 g/l) was carried out in continuously stirred tank reactors (CSTRs) at 35 degrees C. COD stabilization between 36% and 55% and methane yields between 0.114 and 0.184 l/g COD added were achieved. However, the process was strongly inhibited, presumably by sodium, and unstable, with propionic acid being the main compound of the volatile fatty acids (VFA). When diluting the sludge 1:1 with tap water (Na: 5.3 g/l), the inhibition could be overcome and a stable process with low VFA concentrations was achieved. The results of the study are used to make recommendations for the configuration of full-scale treatment plants for the collected sludge from one salmon farming licence and to estimate the energy production from these plants.     

Growth monitoring of <Emphasis Type="Italic">Fibrobacter succinogenes</Emphasis> by pressure measurement

In life support systems, such as the MELiSSA (Micro-Ecological Life Support Alternative) project, developed by the European Space Agency, the aim is to understand and assemble artificial ecosystems for ensuring human subsistence in space. Fibrobacter succinogenes, an anaerobic bacterium, was used for the degradation of vegetable wastes produced in higher plants chambers, but the process does not allow the monitoring of biomass concentration and degradation rates. This study proposes a growth and a degradation monitoring technique using pressure measurements. First, volatile fatty acids (VFA) production was compared with biomass growth and with CO₂ production. The experiments were carried out in batch and fed-batch processes on glucose and on vegetables. The results have shown that a link could be established between VFA production, degradation rate and gas pressure measurements. Thus, the pressure could be used both as a relevant variable for online evaluation of biomass growth and of degradation of complex vegetable wastes.     

Solid-state fermentation for production of griseofulvin on rice bran using Penicillium griseofulvum

Griseofulvin is a secondary metabolite produced from fungal species that have morphology suitable for solid-state fermentation (SSF). Reports on production of griseofulvin by SSF are scarce. The present work investigates SSF for griseofulvin production, optimization of its process parameters vis-à-vis the conventional submerged fermentation and its downstream processing from the same. Rice bran adjusted to an initial moisture content (IMC) of 50% (v/w) inoculated with 1 mL of a suspension of 10(6) spores/mL under agitation at 250 rpm containing the modified Czapek-Dox medium and additional 0.1% choline chloride as a precursor gave a yield of griseofulvin in 9 days that was comparable to submerged fermentation after 28 days. The yield of griseofulvin (microg/g dry biomass) was comparable in SSF and submerged fermentation. The biomass was estimated by estimation of chitin. Discussions on the effect of each parameter in SSF have also been included.     

Optimization of the medium composition for production of mycelial biomass and exo-polymer by Grifola frondosa GF9801 using response surface methodology

In this work, a three-level Box-Behnken factorial design was employed combining with response surface methodology (RSM) to optimize the medium composition for the production of the mycelial biomass and exo-polymer in submerged cultures by Grifola frondosa GF9801. A mathematical model was then developed to show the effect of each medium composition and their interactions on the production of mycelial biomass and exo-polymer. The model estimated that, a maximal yield of mycelial biomass (17.61 g/l) could be obtained when the concentrations of glucose, KH2PO4, peptone were set at 45.2 g/l, 2.97 g/l, 6.58 g/l, respectively; while a maximal exo-polymer yield (1.326 g/l) could be achieved when setting concentrations of glucose, KH2PO4, peptone at 58.6 g/l, 4.06 g/l and 3.79 g/l, respectively. These predicted values were also verified by validation experiments. Compared with the values obtained by other runs in the experimental design, the optimized medium resulted in a significant increase in the yields of mycelial biomass and exo-polymer. Maximum mycelial biomass yield of 22.50 g/l was achieved in a 15-l fermenter using the optimized medium.     

High-density spore production of Piriformospora indica, a plant growth-promoting endophyte, by optimization of nutritional and cultural parameters

Piriformospora indica is an axenically cultivable root endophytic fungus which exerts plant growth promoting effects on its host plants. To enable commercial production of its spores, the medium composition and culture conditions have been optimized in a 14 L bioreactor such that they result in maximum biomass during growth phase and in maximum spore yield during subsequent sporulation phase. Maximum spore yields were obtained with modified Kaefer medium using a glucose deprivation strategy. An enhancement of 100% in overall biomass productivity (0.18 g L(-1) h(-1)) and reduction of about 70% in the time (60 h) required to achieve the maximum spore yield (9.25×10(7) spores/mL) was achieved in comparison to the original Kaefer medium. The high spore yield obtained in the present study seems to be economical for commercial production of P. indica.     

Biological decolorization of xanthene dyes by anaerobic granular biomass

Biodegradation of a xanthene dyes was investigated for the first time using anaerobic granular sludge. On a first screening, biomass was able to decolorize, at different extents, six azo dye solutions: acid orange 7, direct black 19, direct blue 71, mordant yellow 10, reactive red 2 and reactive red 120 and two xanthene dyes--Erythrosine B and Eosin Y. Biomass concentration, type of electron donor, induction of biomass with dye and mediation with activated carbon (AC) were variables studied for Erythrosine B (Ery) as model dye. Maximum color removal efficiency was achieved with 4.71 g VSS L?1, while the process rates were independent of the biomass concentration above 1.89 g VSS L?1. No considerable effects were observed when different substrates were used as electron donors (VFA, glucose or lactose). Addition of Ery in the incubation period of biomass led to a fivefold increase of the decolorization rate. The rate of Ery decolorization almost duplicated in the presence of commercial AC (0.1 g L?1 AC?). Using different modified AC samples (from the treatment of AC?), a threefold higher rate was obtained with the most basic one, AC(H?), as compared with non-mediated reaction. Higher rates were obtained at pH 6.0. Chemical reduction using Na?S confirmed the recalcitrant nature of this dye. The results attest that decolorization of Ery is essentially due to enzymatic and adsorption phenomena.     

Optimization of Exopolysaccharide Overproduction by Lactobacillus confusus in Solid State Fermentation under High Salinity Stress

It is believed that high concentrations of sodium chloride (NaCl) suppress the biosynthesis of exopolysaccharide (EPS) in lactic acid bacteria (LAB). Nevertheless, overproduction of EPSs due to high salinity stress in solid state fermentation performed on an agar surface was demonstrated in this study using a response surface methodology via a central composite design (CCD). Under optimized conditions with NaCl 4.97% and sucrose 136.5 g/L at 40.79 h of incubation, the EPS yield was 259% (86.36 g/L of EPS), higher than the maximum yield produced with the modified MRS medium containing only 120 g/L of sucrose without NaCl (33.4 g/L of EPS). Biosynthesis of EPS by Lactobacillus confusus TISTR 1498 was independent of biomass production. Our results indicated that high salinity stress can enhance EPS production in solid state fermentation.     

Production of thuringiensin from Bacillus thuringiensis using a net-draft-tube,modified airlift reactor

A net-draft-tube, modified airlift reactor and a stirred-tank reactor were used for thuringiensin production by Bacillus thuringiensis subsp. darmstadiensis growing with various concentrations of molasses. The optimum concentration of molasses for thuringiensin production in both reactors was 15 g/l. There was a 6 h delay in sporulation in the modified airlift reactor compared with that in the stirred-tank reactor. Thuringiensin yield in the modified airlift reactor (2.2 g/l) was consequently higher than that in the stirred-tank reactor (1.1 g/l).