From agro-industrial wastes to single cell oils: a step towards prospective biorefinery

The reserves of fossil-based fuels, which currently seem sufficient to meet the global demands, is inevitably on the verge of exhaustion. Contemporary raw material for alternate fuel like biodiesel is usually edible plant commodity oils, whose increasing public consumption rate raises the need of finding a non-edible and fungible alternate oil source. In this quest, single cell oils (SCO) from oleaginous yeasts and fungi can provide a sustainable alternate of not only functional but also valuable (polyunsaturated fatty acids (PUFA)-rich) lipids. Researches are been increasingly driven towards increasing the SCO yield in order to realize its commercial importance. However, bulk requirement of expensive synthetic carbon substrate, which inflates the overall SCO production cost, is the major limitation towards complete acceptance of this technology. Even though substrate cost minimization could make the SCO production profitable is uncertain, it is still essential to identify suitable cheap and abundant substrates in an attempt to potentially reduce the overall process economy. One of the most sought-after in-expensive carbon reservoirs, agro-industrial wastes, can be an attractive replacement to expensive synthetic carbon substrates in this regard. The present review assess these possibilities referring to the current experimental investigations on oleaginous yeasts, and fungi reported for conversion of agro-industrial feedstocks into triacylglycerols (TAGs) and PUFA-rich lipids. Multiple associated factors regulating lipid accumulation utilizing such substrates and impeding challenges has been analyzed. The review infers that production of bulk oil in combination to high-value fatty acids, co-production strategies for SCO and different microbial metabolites, and reutilization and value addition to spent wastes could possibly leverage the high operating costs and help in commencing a successful biorefinery. Rigorous research is nevertheless required whether it is PUFA-rich oil production (for competing with algal omega oils) or neutral bulk oil production (for overcoming yield limitations and managing process economy) to establish this potential source as future resource.     

PEGylation of lysine residues improves the proteolytic stability of fibronectin while retaining biological activity

Excessive proteolysis of fibronectin (FN) impairs tissue repair in chronic wounds. Since FN is essential in wound healing, our goal is to improve its proteolytic stability and at the same time preserve its biological activity. We have previously shown that reduced FN conjugated with polyethylene glycol (PEG) at cysteine residues is more proteolytically stable than native FN. Cysteine‐PEGylated FN supported cell adhesion and migration to the same extent as native FN. However, unlike native FN, cysteine‐PEGylated FN was not assembled into an extracellular matrix (ECM) when immobilized. Here, we present an alternative approach in which FN is preferentially PEGylated at lysine residues using different molecular weight PEGs. We show that lysine PEGylation does not perturb FN secondary structure. PEG molecular weight, from 2 to 10 kDa, positively correlates with FN–PEG proteolytic stability. Cell adhesion, cell spreading, and gelatin binding decrease with increasing molecular weight of PEG. The 2‐kDa FN–PEG conjugate shows comparable cell adhesion to native FN and binds gelatin. Moreover, immobilized FN–PEG is assembled into ECM fibrils. In summary, lysine PEGylation of FN can be used to stabilize FN against proteolytic degradation with minimal perturbation to FN structure and retained biological activity.     

Mapping quantitative trait loci for root development under hypoxia conditions in soybean (<Emphasis Type="Italic">Glycine max</Emphasis> L. Merr.)

Key message

Greatest potential, QTLs for hypoxia and waterlogging tolerance in soybean roots were detected using a new phenotypic evaluation method.

Abstract

Waterlogging is a major environmental stress limiting soybean yield in wet parts of the world. Root development is an important indicator of hypoxia tolerance in soybean. However, little is known about the genetic control of root development under hypoxia. This study was conducted to identify quantitative trait loci (QTLs) responsible for root development under hypoxia. Recombinant inbred lines (RILs) developed from a cross between a hypoxia-sensitive cultivar, Tachinagaha, and a tolerant landrace, Iyodaizu, were used. Seedlings were subjected to hypoxia, and root development was evaluated with the value change in root traits between after and before treatments. We found 230 polymorphic markers spanning 2519.2 cM distributed on all 20 chromosomes (Chrs.). Using these, we found 11 QTLs for root length (RL), root length development (RLD), root surface area (RSA), root surface area development (RSAD), root diameter (RD), and change in average root diameter (CARD) on Chrs. 11, 12, 13 and 14, and 7 QTLs for hypoxia tolerance of these root traits. These included QTLs for RLD and RSAD between markers Satt052 and Satt302 on Chr. 12, which are important markers of hypoxia tolerance in soybean; those QTLs were stable between 2 years. To validate the QTLs, we developed a near-isogenic line with the QTL region derived from Iyodaizu. The line performed well under both hypoxia and waterlogging, suggesting that the region contains one or more genes with large effects on root development. These findings may be useful for fine mapping and positional cloning of gene responsible for root development under hypoxia.

     

Capitalizing on multi-element interactions through balanced nutrition — A pathway to improve nitrogen use efficiency in China,India and North America

A viable option for increasing nitrogen (N) use efficiency and mitigation of negative impacts of N on the environment is to capitalize on multi-element interactions through implementation of nutrient management programs that provide balanced nutrition. Numerous studies have demonstrated the immediate efficacy of this approach in the developing regions like China and India as well as developed countries in North America. Based on 241 site-years of experiments in these countries, the first-year N recovery efficiency (RE) for the conventional or check treatments averaged 21% while the balanced treatments averaged 54% RE, for an average increase of 33% in RE due to balanced nutrition. Effective policies to promote adoption are most likely those that enable site-specific approaches to nutrient management decisions rather than sweeping, nation-wide incentives supporting one nutrient over another. Local farmers, advisers and officials need to be empowered with tools and information to help them define necessary changes in practices to create more balanced nutrient management.     

Differential role of microenvironment in microencapsulation for improved cell tolerance to stress

The effect of the microenvironment in alginate–chitosan–alginate (ACA) microcapsules with liquid core (LCM) and solid core (SCM) on the physiology and stress tolerance of Sacchromyces cerevisiae was studied. The suspended cells were used as control. Cells cultured in liquid core microcapsules showed a nearly twofold increase in the intracellular glycerol content, trehalose content, and the superoxide dismutase (SOD) activity, which are stress tolerance substances, while SCM did not cause the significant physiological variation. In accordance with the physiological modification after being challenged with osmotic stress (NaCl), oxidative stress (H₂O₂), ethanol stress, and heat shock stress, the cell survival in LCM was increased. However, SCM can only protect the cells from damaging under ethanol stress. Cells released from LCM were more resistant to hyperosmotic stress, oxidative stress, and heat shock stress than cells liberated from SCM. Based on reasonable analysis, a method was established to estimate the effect of microenvironment of LCM and SCM on the protection of cells against stress factors. It was found that the resistance of LCM to hyperosmotic stress, oxidative stress, and heat shock stress mainly depend on the domestication effect of LCM’s microenvironment. The physical barrier of LCM constituted by alginate–chitosan membrane and liquid alginate matrix separated the cells from the damage of oxidative stress and ethanol stress. The significant tolerance against ethanol stress of SCM attributed to the physical barrier consists of solid alginate–calcium matrix and alginate–chitosan membrane.     

Structural Basis for the Biological Effects of Pr(III) Ions: Alteration of Cell Membrane Permeability

The biological effects of rare-earth ions on the organism have been studied using Pr³⁺ as a probe ion and Escherichia coli cell as a target. Atomic force microscopy (AFM) observation of the surface of E. coli cells shows that the presence of Pr³⁺ substantially changes the structure of the outer membrane. By induced coupled plasma-mass spectrometry (ICP-MS), more Cu²⁺ was found in the cells grown in the presence of Pr³⁺, indicating changes of cell permeability. Using energy dispersive X-ray spectroscopy (EDX), Ca²⁺ is found on the outer surface of the original cell. It is proposed that Pr³⁺ can replace Ca²⁺ from the binding sites because of their close ionic radii and similar ligand speciality.     

Purification and characterization of thermostable H<Subscript>2</Subscript>O<Subscript>2</Subscript>-forming NADH oxidase from 2-phenylethanol-assimilating <Emphasis Type="Italic">Brevibacterium</Emphasis> sp. KU1309

A cytoplasmic NADH oxidase (NOX) was purified from a soil bacteria, Brevibacterium sp. KU1309, which is able to grow in the medium containing 2-phenylethanol as the sole source of carbon under an aerobic condition. The enzyme catalyzed the oxidation of NADH to NAD+ involving two-electron reduction of O2 to H2O2. The molecular weight of the enzyme was estimated to be 102 kDa by gel filtration and 57 kDa by SDS-PAGE, which indicates that the NOX was a homodimer consisting of a single subunit. The enzyme was stable up to 70 degrees C at a broad range of pH from 7 to 11. The enzyme activity increased about ten-fold with the addition of ammonium salt, while it was inhibited by Zn2+ (39%), Cu2+ (41%), Hg2+ (72%) and Ag+ (37%). The enzyme acts on NADH, but not on NADPH. The regeneration of NAD+ utilizing this enzyme made selective oxidation of mandelic acid or L: -phenylalanine possible. This thermostable enzyme is expected to be applicable as a useful biocatalyst for NAD+ recycling.     

二元融合子与荧光假单胞菌耐药性遗传标记的筛选

应用定性和定量药物敏感性试验与诱变相结合,筛选出荧光假单胞菌56-12-10菌株的遗传标记为链霉素抗性,二元融合子AM-1菌株的遗传标记为环丙沙星抗性,确定了在这两种细菌原生质体融合试验中,选择培养基中链霉素的应用浓度为300Iu/ml,环丙沙星应用浓度为100Iu/ml。