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Insects rely on olfaction to locate their host plants by antennae in complex chemical environments. Odorant receptor (OR) genes are thought to play a crucial role in the process. ORs function together with odorant coreceptors to determine the specificity and sensitivity of olfactory reception. The dark black chafer, Holotrichia parallela Motschulsky (Coleoptera: Scarabaeidae), is a destructive underground pest. To understand the molecular basis of H. parallela olfactory reception, an olfactory-biased expressed odorant receptor HparOR27 and HparOrco (HparOR40) were identified from antennal transcriptome analysis and prediction of the sequence structure. Tissue expression analysis showed that HparOR27 was mainly expressed in adult antennae throughout developmental stages. The functions of HparOR27 were analyzed using the Xenopus laevis oocyte expression system. HparOR27 was broadly responsive to three host plant volatiles, including hexanal, lauric acid, and tetradecane. Electroantennogram tests confirmed that three ligands were electrophysiologically active in antennae of female adults. A Y-tube olfactometer test indicated that hexanal was a repellent for adults of both sexes. Taken together, our data support the identification of odorant receptors and provide a molecular basis for eco-friendly pest control.

Background Many herbivore-induced volatiles have been proven to act as signaling compounds to regulate nearby plant defense responses. However, the precise roles of key volatiles produced by maize roots after Holotrichia parallela larva feeding remain largely unknown. Results In the current research, we investigated the changes in phytohormones and volatiles in maize roots after H. parallela larval infestation. Markedly increased contents of the phytohormone jasmonic acid (JA) and the volatiles jasmone and tetradecane were induced by herbivores, whereas the content of salicylic acid (SA) decreased. In addition, pre-exposure to tetradecane markedly increased the levels of the stress hormone JA, its precursors and derivatives, and related gene expression, and pre-exposure altered the production of defensive benzoxazinoid secondary metabolites, resulting in increased plant resistance to H. parallela larvae. Plants pre-exposed to jasmone did not differ from the control plants. Additionally, bioassays showed that H. parallela larval growth was suppressed by feeding maize roots after pre-exposure to tetradecane. Conclusion These results demonstrate that tetradecane may function as a potent defense induction signal that prepares neighboring plants for incoming attacks. This article is protected by copyright. All rights reserved.

Oleaginous yeast Cryptococcus curvatus MUCL 29819, an acid-tolerant lipid producer, was tested to spill lipids extracellularly using different concentrations of acetic acid as carbon source. Extracellular lipids were released when the yeast was cultured with acetic acid exceeding 20g/L. The highest production of lipid (5.01g/L) was obtained when the yeast was cultured with 40g/L acetic acid. When the yeast was cultivated with moderate concentration (20g/L) of acetic acid, lipid production was further increased by 49.6% through preculture with 40g/L acetic acid as stimulant. When applying high concentration (40g/L) of acetic acid as carbon source in sequencing batch cultivation, extracellular lipids accounted up to 50.5% in the last cycle and the extracellular lipids reached 5.43g/L through the whole process. This study provides an effective strategy to enhance extracellular lipid production and facilitate the recovery of microbial lipids.

The oleaginous yeast Cryptococcus curvatus ATCC 20509 can use 5–40 g/L of acetic, propionic, or butyric acid as sole carbon source to produce lipids. High concentrations (30 g/L) of mixed volatile fatty acids (VFAs) were used to cultivate C. curvatus to explore the effects of different ratios of mixed VFAs on lipid production and composition. When mixed VFAs (VFA ratio was 15:5:10) were used as carbon sources, the highest cell mass and lipid concentration were 8.68 g/L and 4.93 g/L, respectively, which were significantly higher than those when 30 g/L of acetic acid was used as sole carbon source. The highest content and yield of odd-numbered fatty acids were 45.1% (VFA ratio was 0:15:15) and 1.62 g/L (VFA ratio was 5:15:10), respectively. These results indicate that adjusting the composition ratios of mixed VFAs effectively improves microbial lipid synthesis and the yield of odd-numbered fatty acids.

The lower utilization ratios of high-content VFAs resulted in less lipid yield by the oleaginous yeast Cryptococcus curvatus ATCC 20509. In this work, increasing the inoculation concentration to OD600=5.1 improved the acetic acid utilization ratio (99.8%) and lipids production (4.63g/L) in mediums with 30g/L of acetic acid. For the higher acetic acid concentration (40g/L), increasing the nitrogen to carbon ratio (0.033) and raising the initial pH (pH=8) was superior over improvement in the inoculate, with the lipid production increased from 1.08g/L to 6.49g/L. Subsequently, mixed VFAs at concentrations of 30g/L and 40g/L were used as the carbon source to simulate waste-derived VFAs. High lipid production (4.82 and 7.45g/L, respectively) was correspondingly achieved with similar high lipid yield (0.187g/g). This study provides an effective strategy to enhance the bioconversion of high-content VFAs into microbial lipids.

A novel process was proposed for the utilization of potash feldspar by roasting in the presence of sodium carbonate. The effects of roasting temperature, granularity, molar ratio of sodium carbonate to potash feldspar and roasting time on the silica extraction rate were investigated. Under the optimal roasting conditions, the silica extraction rate was 98%. The optimal conditions, determined using an orthogonal experiment, were found to be roasting temperature of 875 °C, potash feldspar granularity of 74–89 μm, molar ratio of sodium carbonate to potash feldspar of 1.2:1, and roasting time of 80 min. The kinetics of potash feldspar roasting in the presence of sodium carbonate was described by the shrinking core model and the reaction rate was found to be controlled by the chemical reaction at the particle surface. According to the Arrhenius expression, the activation energy was 164.99 kJ/mol, and the process could be expressed as [1-(1-α)1/3]=2.66×105 exp[-164990/(RT)] t.

Four mixed volatile fatty acids (VFAs) were used as sole carbon source to culture oleaginous yeast Cryptococcus curvatus by sequencing batch culture strategy. The highest lipid content (42.7%) and concentration (1.77 g/L) were achieved when the ratio of VFAs (acetic, propionic, and butyric acids) was 6:3:1. The oleaginous yeast favored to use VFAs for lipid biosynthesis rather than cell proliferation. With regard to the utilization ratio of VFAs, acetic acid reached over 99%, whereas propionic acid was barely 35%. The produced lipids contained nearly 45% of monounsaturated fatty acids, which can be the ideal raw materials for biodiesel production. Additionally, the produced odd-numbered fatty acid content reached 23.6% when the propionate acid content of VFAs was 50%. Further analysis showed that increasing the ratio of acetic acid was most beneficial to cell mass and lipid production, whereas propionic acid and butyric acid were more conducive to lipid and cell mass synthesis, respectively.

Rhodosporidium toruloides AS 2.1389 was tested using different concentrations of acetic acid as a low-cost carbon source for the production of microbial lipids, which are good raw materials for biodiesel production. It grew and had higher lipid contents in media containing 4-20 g/L acetic acid as the sole carbon source, compared with that in glucose-containing media under the same culture conditions. At acetic acid concentrations as high as 20 g/L and the optimal carbon-to-nitrogen ratio (C/N) of 200 in a batch culture, the highest biomass production was 4.35 g/L, with a lipid content of 48.2%. At acetic acid concentrations as low as 4 g/L, a sequencing batch culture (SBC) with a C/N of 100 increased biomass production to 4.21 g/L, with a lipid content of 38.6%. These results provide usable culture strategies for lipid production by R. toruloides AS 2.1389 when using diverse waste-derived volatile fatty acids.

The effect of different iron additives on biodiesel production from activated sludge was investigated under an optimal lipid accumulation condition (pH = 4 & C/N = 100). Iron addition, ranging from 0.1 to 2.5 mmol L−1, had a positive effect on biodiesel production. Among separate iron tests, 0.25 mmol L−1 nZVI and 2.5 mmol L−1 FeCl3 performed the best. The gravimetric fatty acid methyl ester yields of the two treatments reached 215.3 (0.25 mmol L−1 nZVI) and 274.9 mg g−1 dry sludge (2.5 mmol L−1 FeCl3) and increased by 36.1% and 74.0% compared with control run (131.0 mg g−1 dry sludge), respectively. At the end of the culture period, the genus Gluconacetobacter (56.4%) was enriched in the sludge under the 2.5 mmol L−1 FeCl3 treatment while the other treatments were only dominated by Gluconobacter (∼80%). The accumulated lipids mainly contained around 60% of monounsaturated fatty acids, indicating the suitability for biodiesel production. Furthermore, indicators related to production costs showed iron addition could notably improve the biotechnical feasibility.

Surfactin, one of the most effective biosurfactants, has great potential in commercial applications. Studies on effective methods to reduce surfactin's production cost are always a hotspot in the research field of biosurfactants. The aim of this study was to reveal the role of Mn2+ in promoting the biosynthesis of surfactin by Bacillus subtilis ATCC 21332, which could arise more targeted suggestions on surfactin yield promotion. In this study, B.subtilis was cultivated in media containing different Mn2+ concentrations. The obtained results showed that the yield of surfactin gradually increased upon Mn2+ addition (0.001 to 0.1 mmol/L) and achieved the maximal production of 1500 mg/L, which reached 6.2-fold of the yield obtained in media without Mn2+ addition. Correspondingly, the usage ratios of ammonium nitrate were improved. When the Mn2+ concentration was higher than 0.05 mmol/L, nitrate became the main nitrogen source, instead of ammonium, indicating that the nitrogen utilization pattern was also changed. An increase in nitrate reductase activity was observed and the increase upon Mn2+ dosage had a positive correlate with nitrate use, and then stimulated secondary metabolic activity and surfactin synthesis. On the other hand, Mn2+ enhanced the glutamate synthase activity, which increased nitrogen absorption and transformation and provided more free amino acids for surfactin synthesis.

With use of iodine as an appropriate oxidant, unprotected and unmodified aldoses undergo oxidative amidation with a variety of functionalized amines, alpha-amino esters, and peptides, whereas KDO, sialic acid, and other alpha-keto acids proceed with oxidative decarboxylation followed by in situ amidation. Glycoside bond and many other functional groups are inert under such mild reaction conditions. This reaction protocol for direct ligation of carbohydrate molecules looks promising in the development of a general and efficient synthesis of glycoconjugates.

Pure volatile fatty acid (VFA) solution derived from waste activated sludge (WAS) was used to produce microbial lipids as culture medium in this study, which aimed to realize the resource recovery of WAS and provide low-cost feedstock for biodiesel production simultaneously. Cryptococcus curvatus was selected among three oleaginous yeast to produce lipids with VFAs derived from WAS. In batch cultivation, lipid contents increased from 10.2% to 16.8% when carbon to nitrogen ratio increased from about 3.5 to 165 after removal of ammonia nitrogen by struvite precipitation. The lipid content further increased to 39.6% and the biomass increased from 1.56 g/L to 4.53 g/L after cultivation for five cycles using sequencing batch culture (SBC) strategy. The lipids produced from WAS-derived VFA solution contained nearly 50% of monounsaturated fatty acids, including palmitic acid, heptadecanoic acid, ginkgolic acid, stearic acid, oleic acid, and linoleic acid, which showed the adequacy of biodiesel production.