Simulation of fermentation conditions for vitamin B12 biosynthesis from whey

Vitamin B₁₂ production in fermentation of Propionibacterium shermanii and Propionibacterium arl AKU 1251 in whey permeate medium has been studied. The observed results and simulated expected values obtained by fitting statistical equations to the recorded data showed that 24 h old inoculum, 5 mg iron l^?1 and 4% whey lactose were optimal for vitamin B₁₂ biosynthesis in both strains when fermentation was carried out under anerobic (84 h) and aerobic (84 h) conditions at 30°C. The supplementation of whey medium with 0.5% (NH₄)₂HPO₄ enhanced further the metabolite yield; however, the preference for a mixed carbon source (lactose + d-glucose or lactose + d-fructose) at different levels varied in the strains under study. P. shermanii, under optimal cultural conditions, was found to be a better strain than Propionibacterium arl AKU, 1251 in fermenting whey lactose for product (vitamin B₁₂) formation.     

Automatic whole broth multi-fermentor sampling

Summary An efficient, aseptic method of obtaining whole broth fermentation samples was developed based on a piston-valve, a local sample loop, and an ability to drive the entire sample volume with sterile air through a sample line and into a remote tube. The configuration delivers 10-ml samples 10 m away with about 4 ml of broth wasted in the sampling process. An autosampler was enhanced and programmed to control acquisition into chilled tubes. The autosampler-based system represents a convenient way to provide frequent samples to profile intracellular and extracellular components for yeast and bacterial fermentations. A configuration to provide sampling from six fermentors with a multi-rack autosampler will be presented.     

Separation of algal mixtures and bacterial mixtures with flow-microfluorometer using chlorophyll and ethidium bromide fluorescence

The applicability of flow-microfluorometer to separate microbial cells was demonstrated with algal and bacterial cells. Algal mixtures were sorted according to the natural chlorophyll fluorescence and the bacterial mixtures were sorted according to the fluorescence of ethidium bromide-stained nucleic acid.Abbreviation FMF Flow-microfluorometer     

Net effect of wort osmotic pressure on fermentation course, yeast vitality, beer flavor, and haze

The net effect of increased wort osmolarity on fermentation time, bottom yeast vitality and sedimentation, beer flavor compounds, and haze was determined in fermentations with 12° all-malt wort supplemented with sorbitol to reach osmolarity equal to 16° and 20°. Three pitchings were performed in 12°/12°/12°, 16°/16°/12°, and 20°/20°/12° worts. Fermentations in 16° and 20° worts decreased yeast vitality measured as acidification power (AP) by a maximum of 10%, lowered yeast proliferation, and increased fermentation time. Repitching aggravated these effects. The 3rd “back to normal” pitching into 12° wort restored the yeast AP and reproductive abilities while the extended fermentation time remained. Yeast sedimentation in 16° and 20° worts was delayed but increased about two times at fermentation end relative to that in 12° wort. Third “back-to-normal” pitching abolished the delay in sedimentation and reduced its extent, which became nearly equal in all variants. Beer brewed at increased osmolarity was characterized by increased levels of diacetyl and pentanedione and lower levels of dimethylsulfide and acetaldehyde. Esters and higher alcohols displayed small variations irrespective of wort osmolarity or repitching. Increased wort osmolarity had no appreciable effect on the haze of green beer and accelerated beer clarification during maturation. In all variants, chill haze increased with repitching.     

Xylose anaerobic conversion by open-mixed cultures

Xylose is, after glucose, the dominant sugar in agricultural wastes. In anaerobic environments, carbohydrates are converted into volatile fatty acids and alcohols. These can be used as building blocks in biotechnological or chemical processes, e.g., to produce bioplastics. In this study, xylose fermentation by mixed microbial cultures was investigated and compared with glucose under the same conditions. The product spectrum obtained with both substrates was comparable. It was observed that, in the case of xylose, a higher fraction of the carbon was converted into catabolic products (butyrate, acetate, and ethanol) and the biomass yield was approximately 20% lower than on glucose, 0.16 versus 0.21 Cmol X/Cmol S. This lower yield is likely related to the need of an extra ATP during xylose uptake. When submitted to a pulse of glucose, the population cultivated on xylose could instantaneously convert the glucose. No substrate preference was observed when glucose and xylose were fed simultaneously to the continuously operated bioreactor.     

Ground cover and slope exposure effects on micro- and mesobiota in forest soils

The interrelation of Alpine topography with the micro − and mesobiota is still poorly understood. We investigated the effects of ground cover type and slope exposure on the soil microbial biomass (double-stranded DNA, dsDNA) and abundances (real time PCR, qPCR); hydrolytic enzyme activities; and enchytraeid community structure in top soils (2.5-cm increments depth) in subalpine forests in the Italian Alps. Dominant ground covers were grass, moss, litter and woody debris at the north- and the south-facing slopes. The autochthonous soil microbiota (bacteria, fungi and archaea) was quantified by qPCR in the extracellular (eDNA) and intracellular fraction (iDNA) of the total soil DNA pool. A higher eDNA/iDNA ratio indicative of lower microbial activity was recorded in the deepest layer of the grass plots at the north-facing slope. This can be related to a lower degradation of eDNA and/or to an accumulation of eDNA with increasing depth as a result of leaching. The exposure effect was enzyme-specific and higher activities occurred under woody debris primarily at the south-facing slope. These plots also showed a higher nutrient content and a greater microbial biomass assessed as dsDNA yields. Total microannelid abundance was elevated on north-facing slopes on account of strong acidity indicator species. This was related to soil pH being one unit lower compared to the south-facing slope. The thickness of the organic layer (OL + OF + OH) was elevated at the north-facing slope due to a considerably thicker OH-horizon. The vast majority of microannelids at this slope occurred in the organic layer, while at south exposure they were almost evenly distributed between the organic layer and the mineral soil (A-horizon). Exposure was found to be more determinative for the composition of microannelid assemblages than the ground cover type.     

The effect of internal capacitance on power quality and energy efficiency in a tubular microbial fuel cell

The pseudo-capacitive behaviour of a high surface area carbon veil electrode in a tubular microbial fuel cell (MFC) was investigated as a mechanism to enhance power quality and energy efficiency. Accumulated charge and energy from the anodic biofilm after prolonged open circuit times (1–120 min) were compared against equivalent periods of steady state loading (R = 100–3000 Ω). A significant difference in the amount of accumulated charge with different loads was observed, resulting in 1.051 C (R = 100 Ω) compared to 0.006 C (R = 3 kΩ). The automated application of short open and closed circuit (0.5–10 s) cycles resulted in an increase of power/current production (closed circuit alone), but presented lower efficiency considering entire open and closed period. The cumulative charge on the carbon veil electrode with biofilm was 39,807 C m⁻² at 100 Ω. Electrochemical Impedance Spectroscopy (EIS) showed that the Helmholtz layer presented a double layer capacitance of more than ten times the biofilm on electrode. The results indicate that the capacitive behaviour could be utilized to increase the power quality, i.e. its availability/applicability with respect to the operation of low power consuming devices.     

Luminometric measurement of population activity of genetically modified Pseudomonas fluorescens in the soil

Genetically modified cells of Pseudomonas fluorescens, chromosomally marked with genes for bioluminescence, were inoculated into sterile soil microcosms. During incubation for 90 days, viable cell concentration did not change significantly but light output, measured by luminometry, decreased, indicating reduced metabolic activity due to lack of substrates. Amendment with nutrients resulted in parallel increases in both luminescence and dehydrogenase activity. Luminometry therefore enables rapid monitoring of the activity of populations of luminescence-marked microbial inocula in the soil, with greater sensitivity and selectivity than traditional techniques.     

Facile synthesis and antimicrobial activity of CdS-Ag2S nanocomposites

In this study CdS-Ag₂S nanocomposites for antibacterial activity were synthesized via facile co-precipitation method using PVP as capping agent. The prepared nanocomposites have particle sizes in the range of 50–100 nm (SEM) and PVP addition has good influence on the morphology of nanocomposites. The antimicrobial activity of pure Ag₂S, CdS and CdS-Ag₂S composites was evaluated against Pseudomonas aeruginosa, Staphylococcus aureus and Escherichia coli. The results demonstrate that antibacterial activity was significantly improved due to increasing ratio of CdS into CdS-Ag₂S nanocomposites in comparison to pure Ag₂S and CdS.     

Enhanced endoxylanase production by Myceliophthora thermophila using rice straw and its synergism with phytase in improving nutrition

The goal of the present investigation was to attain the enhanced production of endoxylanase in submerged fermentation using different approaches followed by its utility in improving nutrition of wheat and rice flours along with phytase. Myceliophthora thermophila BJTLRMDU3 produced 51.70 U/mL of xylanase using rice straw as a substrate after optimization with ‘one variable at a time’ approach. After Plackett-Burman design study, sodium nitrate, K₂HPO₄ and Tween 20 were selected as critical factors and further optimized by response surface methodology. Increased xylanase production (80.15 U/mL) was attained with 2.5 % (w/v) sodium nitrate, 1.25 % (w/v) K₂HPO₄, and 2 % (v/v) Tween 20 at 40 °C. An overall 1.5-fold increase in xylanase production was achieved after statistical optimization. Applicability of M. thermophila xylanase (200 U/g flour) alone and in combination with phytase (15 U/g flour) from Aspergillus oryzae SBS50 in wheat and rice flours showed enhancement in nutritional qualities of both flours. About 45.67 %, 29.73 %, and 107.91 % increase in reducing sugars, soluble proteins and inorganic phosphate, respectively in wheat flour, while 94.16 %, 134.52 %, and 473.33 % increase in reducing sugars, soluble proteins and inorganic phosphate, respectively in rice flour was achieved at 60 °C and pH 5.0 by synergistic action of xylanase and phytase as compared to control having only xylanase.