Marjatta Vahvaselkä

The formation and characterisation of ultra-thin films containing Ag nanoparticles

A simple three step method for creating ultra-thin films, which contain Ag nanoparticles, on both glass and stainless steel surfaces, is presented. First, during the immersion into N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane (DIAMO) a monolayer of DIAMO is attached on the sample surface after which immersion in silver nitrate is performed and a complex between the two amino groups of DIAMO and silver ions forms, leading to large clusters on the surface. During the annealing step these silver containing clusters are converted into silver nanoparticles which are homogeneously distributed and bound to the surface. The formation of the film was characterised using UV/Vis, FE-SEM and FE-AES. Additionally, SERS activity of the surface and the effect of the attachment of the nanoparticles on their antibacterial nature were also investigated.

Production of cis-9,trans-11-conjugated linoleic acid in Camelina meal and okara by an oat-assisted microbial process.

A method to obtain cis-9,trans-11-conjugated linoleic acid (c9,t11-CLA) into camelina meal and okara, the byproducts of plant oil processing, is described. The triacylglycerols in these materials were hydrolyzed with the aid of lipolytically active oat flour for 3 weeks at a water activity of 0.70. The resulting free linoleic acid was then isomerized predominantly to c9,t11-CLA by resting cells of Propionibacterium freudenreichii ssp. shermanii in 5% aqueous camelina meal and okara slurries. In camelina meal slurries, c9,t11-CLA content after 21 h of fermentation was 0.83 mg/mL and 96 mg/g of total lipids. In okara slurries, the content of c9,t11-CLA was 1.1 mg/mL and 78 mg/g of total lipids. Doubling the hydrolysis time in okara increased the subsequent content of c9,t11-CLA to 1.4 mg/mL, corresponding to 110 mg/g of total lipids. After isomerization, CLA was concentrated into a particulate material of the slurries by acidification. The results suggest that the method is applicable to a wide spectrum of lipid-containing plant materials to further increase their nutritional value.

Integrating the opposites of biofuel production: Absorption of short-chain alcohols into oleaginous yeast cells for butanol recovery and wet-extraction of microbial oil

Recovery of two biotechnologically produced fuel components, butanol and microbial oil, is assessed by absorption of the six shortest 1-alcohols into oleaginous yeast cells. We show an unexpectedly high extent of absorption of >C3 alcohols from water into Rhodosporidium fluviale cells with a lipid content of 69% of cell dry weight (CDW). Increasing the carbon chain length of the alcohol boosts both the rate and the quantity of absorption of the alcohol from water containing an initial ratio of 9.5 of CDW to alcohol. Under these conditions, 40% of butanol is removed from water, while the methanol concentration remains unchanged in 48 h incubation with the oleaginous yeast cells. Lower absorption of alcohols into non-oleaginous bakers yeast cells as a reference suggests that a majority of the alcohols combines with the lipid droplets inside oleaginous cells. The partition coefficient of the intracellular microbial oil to butanol exceeds those of oleyl alcohol and rapeseed oil by factors of 4 and 16. The capacity of oleaginous yeast cells to absorb butanol reaches 13% of CDW from 48 g per L butanol solution. Leakage of intracellular microbial oil occurs when the initial butanol concentration exceeds approximately 20 g L−1. Butanol can be recovered after absorption from oleaginous yeast biomass, while microbial oil can be separated by subsequent wet-extraction with the alcohols as solvents. These results suggest that synergistic outcomes can be achieved by process integration both for industry and the environment.

Effect of malolactic fermentation on the volatile aroma compounds in four sea buckthorn varieties

Abstract Volatile compound composition of sea buckthorn juice headspace was investigated before and after malolactic fermentation of the juice. Ethyl acetate, 3-methylbutanol and 3-methylbutyl acetate were formed in abundance during fermentation, whereas concentrations of ethyl 2-methypropanoate, ethyl 3-methylbutanoate, ethyl hexanoate and ethyl octanoate decreased.