Lipid yields from oleaginous yeasts isolated from the north Peruvian Andes by culture media non-limiting nitrogen

Oleochemicals can be obtained from oily yeasts due to their ability to produce a high lipid content. This research aimed to isolate them from the North Peruvian Andes with a lipid content greater than 20%. They were identified by sequencing internal transcribed spacer regions ITS of conserved ribosomal DNA (rDNA), evaluate their growth kinetics, biomass and lipid yields, using culture media with C/N 100:1+xylose (MS-1-7) and 2:1+glucose (MS-2-7). Growth kinetics up to the maximum stationary phase was evaluated using the parameterized Gompertz type II model. Rhodotorula glutinis, R. mucilaginosa, and R. kratochvilovae were selected. The C/N ratio in the culture medium influenced growth kinetics, biomass and lipids yields. With MS-1-7, a high specific growth rate (?max) was obtained, reaching the stationary phase between 6 to 9 h and the highest lipid accumulation between 23.1% and 31.5%. With the MS-2-7 medium, maximum biomass value obtained in the stationary phase between 37 and 51 h, which generated the highest biomass yields at the end of the entire process and lipid yield of 4.65, 5.59, and 8.80 g L-1 in the strains mentioned. There is potential to obtain high lipid yields using a culture media non-limiting nitrogen, examining not only the C/N ratio. But also, the quantities, nature of the components, and type of oleaginous yeasts taking care to avoid a high carbon concentration to prevent the Cabtree effect.

Microalgae: The Multifaceted Biomass of the 21st Century

Microalgae are unicellular, eukaryotic organisms which possess unique qualities of replication, producing biomass as a precursor for biofuels, nutraceuticals, biofertilizer, and fine chemicals including hydrocarbons. Microalgae access nitrates and phosphates in wastewater from municipalities, industries, and agricultural processes to grow. Wastewater is, therefore, culture media for microalgae, and provides the needed nutrients, micronutrients, inorganic and organic pollutants to produce microalgae biomass. Suitable strains of microalgae cultivated under mesophilic conditions in wastewater with optimized hydrodynamics, hydraulic retention time (HRT), luminous intensity, and other co-factors produce biomass of high specific growth rate, high productivity, and with high density. The hydrodynamics are determined using a range of bioreactors from raceway ponds, photobioreactors to hybrid reactors. Carbon dioxide is used in the photosynthetic process, which offers different growth stimuli in the daytime and the night-time as the microalgae cultivation technique is navigated between autotrophy, heterotrophy, and mixotrophy resulting in microalgal lipids of different compositions.

Fertigation of Brassica rapa L. using treated landfill leachate as a nutrient recycling option

Optimising nutrient availability and minimising plant metal contamination are vital in sustainable agriculture. This paper reports experiments in which treated leachate was used at different concentrations with predetermined N content for fertigation of Brassica rapa L. (leafy vegetable). An inorganic fertiliser, with N content equivalent to the leachate amount, was also prepared, as well as a control. Growth (leaf length, leaf width and stem height), harvest parameters (total number of leaves, root length and root dry weight) and specific growth rates (mm/day) were determined for three consecutive seasons. The dry weights of leaves, roots and stems in the leachate treatments were within the ranges of 1.95–3.60 g, 1.18–3.60 g and 0.33–1.37 g, with biomasses of 1.75 g, 1.14 g and 0.2 g, respectively, which were higher than those of the control. B. rapa L. fertigated with 25% diluted treated leachate recorded high specific growth rate and a leaf length of 0.53 mm/day and 0.23.17±0.58 cm, respectively (%N=0.023; p less than 0.05). The maximum permissible mineral concentration set by the Food and Agricultural Organization of the United Nations/World Health Organization (FAO/WHO) was compared with that of the grown plants. Treated leachate can increase plant nutrient content.

Evaluating the potential of chitosan/poly(vinyl alcohol) membranes as alternative carrier material for proliferation of Vero cells

Chitosan/poly(vinyl alcohol) (CS/PVA) blend membranes were prepared using the casting method and their physiochemical properties were analyzed using Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). FTIR and XRD demonstrated possible hydrogen bonds between CS and PVA. The addition of PVA to CS resulted in surface roughness as analyzed by SEM. The CS/PVA blend membrane exhibited high tensile properties (81.62%) and reduced water-holding capacity (53.8%) compared to a pure CS membrane (control). Cell viability and proliferation were assessed via an MTT assay with Vero cell culture. Associated with improved physicochemical properties, the CS/PVA blend membrane promotes cell proliferation of Vero cells with high specific growth rate (0.582 day-1). The results demonstrate that the blending of CS and PVA could significantly alter the surface rugosity, water-holding capacity and improve the mechanical and biological properties of the membrane. Interestingly, this concept can be extended for different anchorage-dependent cell lines, as an alternative carrier material.

Poly(3-Hydroxybutyrate) Production from Glycerol by Zobellella denitrificans MW1 via High-Cell-Density Fed-Batch Fermentation and Simplified Solvent Extraction

ABSTRACT Industrial production of biodegradable polyesters such as polyhydroxyalkanoates is hampered by high production costs, among which the costs for substrates and for downstream processing represent the main obstacles. Inexpensive fermentable raw materials such as crude glycerol, an abundant by-product of the biodiesel industry, have emerged to be promising carbon sources for industrial fermentations. In this study, Zobellella denitrificans MW1, a recently isolated bacterium, was used for the production of poly(3-hydroxybutyrate) (PHB) from glycerol as the sole carbon source. Pilot-scale fermentations (42-liter scale) were conducted to scale up the high PHB accumulation capability of this strain. By fed-batch cultivation, at first a relatively high cell density (29.9 ± 1.3 g/liter) was obtained during only a short fermentation period (24 h). However, the PHB content was relatively low (31.0% ± 4.2% [wt/wt]). Afterwards, much higher concentrations of PHB (up to 54.3 ± 7.9 g/liter) and higher cell densities (up to 81.2 ± 2.5 g/liter) were obtained by further fed-batch optimization in the presence of 20 g/liter NaCl, with optimized feeding of glycerol and ammonia to support both cell growth and polymer accumulation over a period of 50 h. A high specific growth rate (0.422/h) and a short doubling time (1.64 h) were attained. The maximum PHB content obtained was 66.9% ± 7.6% of cell dry weight, and the maximum polymer productivity and substrate yield coefficient were 1.09 ± 0.16 g/liter/h and 0.25 ± 0.04 g PHB/g glycerol, respectively. Furthermore, a simple organic solvent extraction process was employed for PHB recovery during downstream processing: self-flotation of cell debris after extraction of PHB with chloroform allowed a convenient separation of a clear PHB-solvent solution from the cells. Maximum PHB recovery (85.0% ± 0.10% [wt/wt]) was reached after 72 h of extraction with chloroform at 30°C, with a polymer purity of 98.3% ± 1.3%.

Microbial and Physiological Characterization of Weakly Amylolytic but Fast-Growing Lactic Acid Bacteria: a Functional Role in Supporting Microbial Diversity in Pozol, a Mexican Fermented Maize Beverage

ABSTRACT Pozol is an acid beverage obtained from the natural fermentation of nixtamal (heat- and alkali-treated maize) dough. The concentration of mono- and disaccharides from maize is reduced during nixtamalization, so that starch is the main carbohydrate available for lactic acid fermentation. In order to provide some basis to understand the role of amylolytic lactic acid bacteria (ALAB) in this fermented food, their diversity and physiological characteristics were determined. Forty amylolytic strains were characterized by phenotypic and molecular taxonomic methods. Four different biotypes were distinguished via ribotyping; Streptococcus bovis strains were found to be predominant. Streptococcus macedonicus, Lactococcus lactis, and Enterococcus sulfureus strains were also identified. S. bovis strain 25124 showed extremely low amylase yield relative to biomass (139 U g [cell dry weight]−1) and specific rate of amylase production (130.7 U g [cell dry weight]−1 h−1). In contrast, it showed a high specific growth rate (0.94 h−1) and an efficient energy conversion yield to bacterial cell biomass (0.31 g of biomass g of substrate−1). These would confer on the strain a competitive advantage and are the possible reasons for its dominance. Transient accumulation of maltooligosaccharides during fermentation could presumably serve as energy sources for nonamylolytic species in pozol fermentation. This would explain the observed diversity and the dominance of nonamylolytic lactic acid bacteria at the end of fermentation. These results are the first step to understanding the importance of ALAB during pozol fermentation.

Isolation and Characterization of Proteolytic Ruminal Bacteria from Sheep and Goats Fed the Tannin-Containing Shrub Legume Calliandra calothyrsus

ABSTRACT Tannins in forages complex with protein and reduce the availability of nitrogen to ruminants. Ruminal bacteria that ferment protein or peptides in the presence of tannins may benefit digestion of these diets. Bacteria from the rumina of sheep and goats fed Calliandra calothyrsus (3.6% N and 6% condensed tannin) were isolated on proteinaceous agar medium overlaid with either condensed (calliandra tannin) or hydrolyzable (tannic acid) tannin. Fifteen genotypes were identified, based on 16S ribosomal DNA-restriction fragment length polymorphism analysis, and all were proteolytic and fermented peptides to ammonia. Ten of the isolates grew to high optical density (OD) on carbohydrates (glucose, cellobiose, xylose, xylan, starch, and maltose), while the other isolates did not utilize or had low growth on these substrates. In pure culture, representative isolates were unable to ferment protein that was present in calliandra or had been complexed with tannin. One isolate, Lp1284, had high protease activity (80 U), a high specific growth rate (0.28), and a high rate of ammonia production (734 nmol/min/ml/OD unit) on Casamino Acids and Trypticase Peptone. Phylogenetic analysis of the 16S ribosomal DNA sequence showed that Lp1284 was related (97.6%) to Clostridium botulinum NCTC 7273. Purified plant protein and casein also supported growth of Lp1284 and were fermented to ammonia. This is the first report of a proteolytic, ammonia-hyperproducing bacterium from the rumen. In conclusion, a diverse group of proteolytic and peptidolytic bacteria were present in the rumen, but the isolates could not digest protein that was complexed with condensed tannin.