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The biosurfactant surfactin has potential to aid in the recovery of energy resources (oil recovery) or subsurface organic contaminants (environmental remediation). However, high medium and purification costs limit its use in these high-volume applications. In previous work, we showed that surfactin could be produced from an inexpensive low-solids potato process effluent with minimal amendments or pretreatments. Previous research has also shown that surfactin can be both produced in cultures and recovered by foam fractionation in an airlift reactor. Results using both purified potato starch and unamended low-solids potato process effluent as substrates for surfactin production indicate that the process is oxygen limited and that recalcitrant indigenous bacteria in the potato process effluent hamper continuous surfactin production. The research reported here features the use of a chemostat operated in batch mode for producing surfactin with concomitant use of antifoam to prevent surfactant loss. The antifoam did not interfere with surfactin recovery by acid precipitation or its efficacy. Initial trials took about 48 h to produce 0.9 g/L of surfactin from potato process effluent. Increasing the oxygen mass transfer by increasing the stirring speed and adding a baffle decreased production time to 12–24 h and produced about 0.6 g/L of surfactin from two different potato-processing facilities.

The feasibility of using cull potatoes as substrate for the simultaneous production of nisin, a natural food preservative, and lactic acid, a raw material for biopolymer production, was studied. Cull potatoes are potato tubers unacceptable for food processing because of size or damage caused by bruising or disease. Although cull potatoes are enriched in various nutrients including starch, minerals, and proteins, they alone still cannot provide enough essential nutrients for the growth and metabolism of subsp. (ATCC 11454). Stimulation of bacterial growth, nisin biosynthesis, as well as lactic acid production was observed when additional nutrients such as yeast extract, peptone from meat, peptone from soy (PS), corn steep solid (CSS), and distillers’ dried grains with solubles were provided. Considering the cost and availability, PS and CSS were selected as nutrient supplements for nisin and lactic acid coproduction. The conditions for nisin biosynthesis and lactic acid coproduction by subsp. in a cull potato-based medium were subsequently optimized using a statistically based experimental design.

The ethanol production cost in a simultaneous saccharification and fermentation-based bioethanol process is influenced by the requirements for yeast production and for enzymes. The main objective of this study was to evaluate—technically and economically—the influence of these two factors on the production cost. Abase case with 5 g/L of baker’s yeast and an initial concentration of water-insoluble solids of 5% resulted in an experimental yield of 85%. When these data were implemented in Aspen Plus, yeast was assumed to be produced from sugars in the hydrolysate, reducing the overall ethanol yield to 69%. The ethanol production cost was 4.80 SEK/L (2.34 US$/gal). When adapted yeast was used at 2 g/L, an experimental yield of 74% was achieved and the estimated ethanol production cost was the same as in the base case. A 50% reduction in enzyme addition resulted in an increased production cost, to 5.06 SEK/L (2.47 US$/gal) owing to reduced ethanol yield.

The stability at room temperature (25°C) of recombinant green fluorescent protein (GFPuv), expressed by cells and isolated by three-phase partitioning extraction with hydrophobic interaction column, was studied. The GFPuv was diluted in buffered (each 10 mM: Tris-HCl, pH 8.0; phosphate, pH 6.0 and 7.0 and acetate, pH 5.0) and in unbuffered (water for injection [WFI]; pH 6.70 ± 0.40) glucose solutions (from 1.5 to 50%). By assaying the loss of fluorescence intensity as a measure of denaturation, the stability of GFPuv in these solutions was evaluated relative to glucose concentration, pH, osmolarity, density, conductivity, and viscosity. The extent of protein denaturation (loss of fluorescence intensity) was expressed in decimal reduction time (-value), the time required to reduce 90% of the initial fluorescence intensity of GFPuv. The -value between 56 and 83 h of GFPuv at 1.5–15% glucose in WFI was equivalent to 20–30% glucose in a phosphate. The stability of GFPuv in 50% glucose was similar for all buffers studied and four times higher than in WFI. By the convenient measure of fluorescence intensity, GFPuv can be used as an indicator to report the extent of denaturation rates of other proteins in glucose solutions.

The performance of immobilized in sodium alginate beads and on a spiral-sheet bioreactor for the production of lactic acid from cheese whey was evaluated. Lactose utilization and lactic acid yield of were compared with those of immobilized in sodium alginate beads showed better performance in lactose utilization and lactic acid yield than . In the spiral-sheet bioreactor, a lactose conversion ratio of 79% and lactic acid yield of 0.84 g of lactic arid/g of lactose utilized were obtained during the first run with the immobilized lactose conversion ratio of 69% and lactic acid yield of 0.51 g of lactic acid/g of lactose utilized were obtained during the first run with immobilized in the spiral-sheet bioreactor. In producing lactic acid performed better when using the Spiral Sheet Bioreactor and showed better performance with gel bead immobilization. Because is a very promising new bacterium for lactic acid production from cheese whey, its optimum fermentation conditions such as pH and metabolic pathway need to be studied further. The ultrafiltration tests have shown that 94% of the cell and cheese whey proteins were retained by membranes with a mol wt cutoff of 5 and 20 KDa.

Foam fractionation cannot be used to recover cellulase from an aerated water solution effectively because cellulase by itself can produce only a small amount of foam. The addition of a surfactant can, however, increase the foamate volume and enhance the concentration of cellulase. We studied three detergents individually added to a 200 mg/L cellulase solution to promote foaming. These detergents were anionic, cationic, and nonionic surfactants, respectively. Although contributing to foam production, it was observed that nonionic surfactant (Pluronic F-68) barely concentrated cellulase, leaving the enrichment ratio unchanged, near 1. With anionic surfactant, sodium dedecyl sulfate, and cationic surfactant, cetyltrimethylammonium bromide (CTAB), the enrichment ratio became much larger, but cellulase denaturation occurred, reducing the activity of the enzyme. When CTAB was used to help foam cellulase, β-cyclodextrin was subsequently added to the foamate to help restore the enzyme activity.

This article reports experimental data on the production of fatty acid ethyl esters from refined and degummed soybean oil and castor oil using NaOH as catalyst. The variables investigated were temperature (30–70°C), reaction time (1–3 h), catalyst concentration (0.5–1.5 w/wt%), and oil-to-ethanol molar ratio (1:3–1:9). The effects of process variables on the reaction conversion as well as the optimum experimental conditions are presented. The results show that conversions >95% were achieved for all systems investigated. In general, an increase in reaction temperature, reaction time, and in oil-to-ethanol molar ratio led to an enhancement in reaction conversion, whereas an opposite trend was verified with respect to catalyst concentration.

Sawdust hydrolysates were investigated for their ability to support cell growth and cellulase production, and for potential inhibition of Rut C30. Simultaneous fermentations were conducted to compare the hydrolysate-based media with the controls having equivalent concentrations of glucose and Avicel cellulose. Six hydrolysates differing in the boiling durations in the hydrolysis procedure were evaluated. The hydrolysates were found to support cell growth and induce active cellulase synthesis. The maximum specific cellulase production rate was 0.046 filter paper units (FPU)/(g of cells · h) in the hydrolysate-based systems, much higher than that (0.017 FPU/[g of cells · h]) in the controls.

The effects of saturated and unsaturated fatty acids (lauric acid, palmitic acid, steric acid, oleic acid, linoleic acid, soybean oil) on ( sp.), and recombinant were studied. Oleic acid enhances Poly-3-hydroxybutyrate (PHB) production in these three bacterial strains, suggesting that the single double bond of the acid activates the polyhydroxylkanoate accumulation enzymatic reaction. Under the effect of lauric acid and linoleic acid, the growth of and were totally inhibited. However, the enhanced PHB accumulation in recombinant was observed.

Hexane is a toxic volatile organic compound that is quite abundant in gas emissions from chemical industries and printing press and painting centers, and it is necessary to treat these airstreams before they discharge into the atmosphere. This article presents a treatment for hexane-contaminated air in steady-state conditions using an internal-loop airlift bioreactor inoculated with a strain. Bioprocesses were conducted at 20-mL/min, a load of 1.26 g/m of CH, and a temperature of 28°C. The results of hexane removal efficiencies were presented as a function of the inoculum size (approx 0.07 and 0.2 g/L) and cell reuse. Bioprocess monitoring comprises quantification of the biomass, the surface tension of the medium, and the hexane concentration in the fermentation medium as well as in the inlet and outlet airstreams. The steady-state results suggest that the variation in inoculum size from 0.07 to 0.2 g/L promotes hexane abatement from the influent from 65 to 85%, respectively. Total hydrocarbon removal from the waste gas was achieved during experiments conducted using reused cells at an initial microbial concentration of 0.2 g/L.