R. Vilu | Tallinn University of Technology (original) (raw)

Papers by R. Vilu

Acta Biotechnologica, 1988

... [11] [12] KAERU, A. IJXDEBS, M., VANATALU, K., VILU, R.: Arch. Microbiol. 133 (1982), 142. [1... more ... [11] [12] KAERU, A. IJXDEBS, M., VANATALU, K., VILU, R.: Arch. Microbiol. 133 (1982), 142. [13] BERCMEYER, HU, BERNT, E., SCHMIDT, F., STORK, H. In: Methods of Enzymatic Analysis [14] Srrto, M.-R., ROMAX, H., LOWREN, T.: Eur. J. Appl. Microbiol. Biotechnol. ...

Journal of General Microbiology, 1993

Bioresource technology, 2014

Lipid and protein rich solid slaughterhouse wastes are attractive co-substrates to increase volum... more Lipid and protein rich solid slaughterhouse wastes are attractive co-substrates to increase volumetric biogas production in co-digestion with dairy manure. Addition of decanter sludge (DS), containing 42.2% of lipids and 35.8% of proteins (total solids basis), up to 5% of feed mixture resulted in a stable process without any indication of long chain fatty acids (LCFA) or free ammonia (NH3) inhibition and in 3.5-fold increase of volumetric biogas production. Contrary, only lipids addition as technical fat (TF) at over 2% of feed mixture resulted in formation of floating granules (FG) and process efficiency decrease. Formed FG had low biodegradability and its organic part was composed of lipids and calcium salts of LCFAs. Anaerobic digestion process intentionally directed to FG formation, could be a viable option for mitigation and control of lipids overload and derived LCFA inhibition.

Biotechnology Techniques, 1995

An automatic fed-batch procedure for the production of recombinant proteins in Escherichia coli w... more An automatic fed-batch procedure for the production of recombinant proteins in Escherichia coli was developed. Using glycerol as carbon source and by controlling the growth rate by using feed-forward algorithm, enabled high specific expression level (10–20 % of total cell protein) at high cell densities (20 g dry wt/l) to be achieved: rat and human soluble catechol-O-methyltransferase, calf prochymosin, and human troponin C were expressed with nearly 50-fold higher volumetric yield compared to the conventional (batch) procedures.

Biotechnology and Bioengineering, 1990

Growth cessation of Escherichia coli in nondialysis fedbatch culture at biomass densities over 30... more Growth cessation of Escherichia coli in nondialysis fedbatch culture at biomass densities over 30-40 g/L has been shown to be the result of the accumulation of acetate, lactate, pyruvate, succinate, propionate, and isobutyrate in the culture broth.' This conclusion was supported by the fact that high cell concentrations (140 g/L) and cellular yields were achieved in dialysis fed-batch culture of E. coli.

Bioresource Technology, 2013

h i g h l i g h t s " Sterilized mass (SM) is an attractive substrate for biogas production. " Hi... more h i g h l i g h t s " Sterilized mass (SM) is an attractive substrate for biogas production. " High TS, fat and proteins content of SM give methane yield of 590.5 m 3 CH4 t Àl . " SM addition of 5% (w/w) to sewage sludge increased methane production 5.7 times. " Free ammonia inhibition threshold value was determined at 596.5 ± 68.6 g NH3 L À1 . " SM addition of 10% (w/w) was detrimental to AD process due to intensive foaming.

Biochimica et Biophysica Acta (BBA) - Molecular Cell Research, 1982

Photoassimilation of 13CO2 and acetate by the photosynthetic bacterium Ctdorobium thiosulfatophil... more Photoassimilation of 13CO2 and acetate by the photosynthetic bacterium Ctdorobium thiosulfatophilum was investigated using 13C-NMR as the method for determination of the labelling pattern of the glucose synthesized by the bacterium. Metabolic pathways functioning in the bacterium were identified by analysis of the multiplet structure of the spectra of tightly coupled systems. The labelling pattern showed that glucose was synthesized in C. thiosulfatophilum mainly by the gluconeogenesis pathway. In agreement with previous investigations, the reserve polysaccharide of C. thiosultatophilum was shown to be polyglucose, with the glucose units linked predominantly a-glucosidic linkages.

Automatica, 1989

ABSTRACT A stochastic control law for the recycling flow of sludge which stabilizes the load char... more ABSTRACT A stochastic control law for the recycling flow of sludge which stabilizes the load characteristic of an aerotank near a given optimal level is proposed. It is shown that the mean square error of stabilization of the load characteristic using the control law proposed is three times less than in the case of conventional control laws.

Archives of Microbiology, 1983

Several growth monitoring parameters, including adenine nucleotide contents, were measured during... more Several growth monitoring parameters, including adenine nucleotide contents, were measured during Escherichia coli K12 batch cultivation in mineral medium with glucose. The adenylate energy charge with its mean value of 0.83 remained roughly stable during growth. The total adenylate and ATP pools (nmol/mg dry weight), and also the individual cell volume changed with a pattern of two maxima at approximately 4 and 10 h of cultivation. After the exhaustion of the glucose from the growth medium the adenylate energy charge, the pools of ATP and total adenylate started to decrease marking the onset of the stationary growth phase. Our data indicate that actually there was only a limited period within the logarithmic growth phase during which the growth might have been balanced: during this period of 1.5 h different growth monitoring parameters (optical absorbance, cell number, total cell volume, and ATP content per ml) increased with almost equal rates. Moreover, as ATP pool and median cell volume during this short period were approximately constant, the culture might have been even in the steady state.

Applied Microbiology and Biotechnology, 2014

Elimination of acetate overflow in aerobic cultivation of Escherichia coli would improve many bio... more Elimination of acetate overflow in aerobic cultivation of Escherichia coli would improve many bioprocesses as acetate accumulation in the growth environment leads to numerous negative effects, e.g. loss of carbon, inhibition of growth, target product synthesis, etc. Despite many years of studies, the mechanism and regulation of acetate overflow are still not completely understood. Therefore, we studied the growth of E. coli K-12 BW25113 and several of its mutant strains affecting acetate-related pathways using the continuous culture method accelerostat (A-stat) at various specific glucose consumption rates with the aim of diminishing acetate overflow. Absolute quantitative exo-metabolome and proteome analyses coupled to metabolic flux analysis enabled us to demonstrate that onset of acetate overflow can be postponed and acetate excretion strongly reduced in E. coli by coordinated activation of phosphotransacetylase-acetyl-CoA synthetase (PTA-ACS) and tricarboxylic acid (TCA) cycles. Fourfold reduction of acetate excretion (2 vs. 8 % from total carbon) at fastest growth compared to wild type was achieved by deleting the genes responsible for inactivation of acetyl-CoA synthetase protein (pka) and TCA cycle regulator arcA. The Δpka ΔarcA strain did not accumulate any other detrimental by-product besides acetate and showed identical μ max and only ~5 % lower biomass yield compared to wild type. We conclude that a fine-tuned coordination between increasing the recycling capabilities of acetate in the PTA-ACS node through a higher concentration of active acetate scavenging Acs protein and downstream metabolism throughput in the TCA cycle is necessary for diminishing overflow metabolism of acetate in E. coli and achieving higher target product production in bioprocesses.

Advances in Environmental Research, 2003

Anaerobic digestion of distillery waste was studied in a mesophilic two-stage system consisting o... more Anaerobic digestion of distillery waste was studied in a mesophilic two-stage system consisting of an anaerobic filter (AF) and an upflow anaerobic sludge blanket (UASB) reactor. The experiments were conducted with hydraulic retention times (HRT) ranging from 10 to 19 days at loading rates of 2.5-5.1 kg CODy(m day) in the first stage, 3 and up to 20-39 days, corresponding to loading rates 0.6-2.5 kg CODy(m day) in the second stage. The treatment 3 efficiencies (COD removals) achieved were 54 and 93% in the first and second stage, respectively. The acidogenic reactor provided satisfactory conversion of initial COD to volatile fatty acids (VFAs), averaging 20.5%. As a result of self-regulation, pH in the methanogenic reactor was in the range of 7.2-7.8. The generation of biogas in the second stage was significantly higher (6 lyday) than that in the first stage (1 lyday). The bacterial growth rate of acetogenicymethanogenic populations, determined by microcalorimetry, was higher in the separated methanogenic stage (average m s0.433 1yh) as compared to the single-stage reactor (acidogenic stage, average m s0.159 1y max max h). To accelerate start-up of the process, increase gas generation and retard production of VFAs in the acidogenic stage small amounts of the algal preparation Biotreat 100 were used.