Chitin Content Research Articles

Purification of Chitin from Pupal Exuviae of the Black Soldier Fly

PurposeChitin purification from remains (pupal exuviae after metamorphosis to adult flies) of Hermetia illucens farming was optimized performing demineralization, deproteinization and bleaching under different conditions. The optimal parameters to obtain high-purity chitin were determined.MethodsDried and ground pupal exuviae, whose composition was initially determined, were demineralized using six different acids. Proteins were removed with a NaOH treatment in which temperature, molarity and duration were varied in a randomized experiment. Bleaching was carried out testing ten different chemicals, including NaOCl, H2O2, solvent mixtures and enzymes. The efficiency of each step was determined to assess the optimal conditions for each of them. The resulting chitin was subjected to spectroscopic characterization.ResultsThe highest demineralization efficiency (90%) was achieved using 0.5 M formic acid for 2 h at 40 °C, confirming the validity of organic acids as a more sustainable alternative to inorganic acids. The treatment with 1.25 M NaOH at 90 °C for 4 h showed the highest deproteinization efficiency, removing 96% of the proteins. Temperature and NaOH concentration were the significant parameters for deproteinization efficiency. The most efficient bleaching treatment was with 6% NaOCl at 60 °C for 1 h (67% efficiency). H2O2 could also be a valid alternative to avoid environmental risk related to chlorine-containing compounds. At the end of the purification process 17% of the original biomass was retained with a chitin content of 85%, corresponding to a chitin yield of 14% related to the initial biomass. Solid-state nuclear magnetic resonance showed that the purified chitin had a degree of acetylation of 96% and X-ray powder diffraction gave a crystallinity index of 74%.ConclusionThis investigation shows an optimized method for extraction of high-purity chitin from H. illucens pupal exuviae, supporting the validity of insect-farming remains as source of this versatile biopolymer.Graphical

Chitin Determination in Residual Streams Derived From Insect Production by LC-ECD and LC-MS/MS Methods

Chitin, a biopolymer present in fungi and arthropods, is a compound of interest for various applications, such as in the agricultural and medical fields. With the recently growing interest in the development of insect farming, the availability of chitin-containing residual streams, particularly the molting skins (exuviae), is expected to increase in the near future. For application purposes, accurate quantification of chitin in these insect sources is essential. Previous studies on chitin extraction and quantification often overlooked the purity of the extracted chitin, making the outcomes inconsistent and prone to overestimation. The present study aims to determine chitin content in the exuviae of three insect species mass-reared worldwide: black soldier fly (BSF), mealworm, and house cricket. Chitin was chemically extracted using acid and alkali treatments to remove minerals and proteins. The purity of extracted chitin was evaluated by hydrolyzing the chitin into glucosamine, followed by quantitative determination of the latter using two liquid chromatography methods: electrochemical detection (ECD) and tandem mass spectrometry (MS/MS). Both methods proved accurate and precise, without the need for labor-intensive derivatization steps. Pearson's correlation and Bland-Altman plots showed that the glucosamine determination results obtained by the two methods were comparable, and there is no consistent bias of one approach vs. the other. The chitin content in extracted residues ranged between 7.9 and 18.5%, with the highest amount found in BSF puparium. In summary, the study demonstrated that (1) the residual streams of the insect farming industry have a great potential for utilization as an alternative chitin source, and (2) both LC-ECD and LC-MS/MS are reliable for the quantitative determination of glucosamine in insect chitin.

The Antifungal Effects of Citral on Magnaporthe oryzae Occur via Modulation of Chitin Content as Revealed by RNA-Seq Analysis.

The natural product citral has previously been demonstrated to possess antifungal activity against Magnaporthe oryzae. The purpose of this study was to screen and annotate genes that were differentially expressed (DEGs) in M. oryzae after treatment with citral using RNA sequencing (RNA-seq). Thereafter, samples were reprepared for quantitative real-time PCR (RT-qPCR) analysis verification of RNA-seq data. The results showed that 649 DEGs in M. oryzae were significantly affected after treatment with citral (100 μg/mL) for 24 h. Kyoto Encyclopedia of Genes and Genomes (KEGG) and a gene ontology (GO) analysis showed that DEGs were mainly enriched in amino sugar and nucleotide sugar metabolic pathways, including the chitin synthesis pathway and UDP sugar synthesis pathway. The results of the RT-qPCR analysis also showed that the chitin present in M. oryzae might be degraded to chitosan, chitobiose, N-acetyl-D-glucosamine, and β-D-fructose-6-phosphate following treatment with citral. Chitin degradation was indicated by damaged cell-wall integrity. Moreover, the UDP glucose synthesis pathway was involved in glycolysis and gluconeogenesis, providing precursors for the synthesis of polysaccharides. Galactose-1-phosphate uridylyltransferase, which is involved in the regulation of UDP-α-D-galactose and α-D-galactose-1-phosphate, was downregulated. This would result in the inhibition of UDP glucose (UDP-Glc) synthesis, a reduction in cell-wall glucan content, and the destruction of cell-wall integrity.

The DOMON domain protein LmKnk contributes to correct chitin content, pore canal formation and lipid deposition in the cuticle of Locusta migratoria during moulting.

Insects prevent uncontrolled penetration of water and xenobiotics by producing an impermeable cuticle. The major component of the cuticle is chitin that adopts a crystalline structure thereby contributing to cuticle stability. Our understanding of the contribution of chitin to the cuticle barrier function is limited. Here, we studied the role of the DOMON domain protein Knickkopf (LmKnk) that is involved in chitin organization and cuticle permeability in the migratory locust Locusta migratoria. We show that LmKnk localizes to the chitin layer in the newly produced cuticle. Injection of double-stranded RNA targeting LmKnk (dsLmKnk) in locust nymphs caused failure of moulting to the next stage. Histological experiments revealed that apolysis, i.e., the detachment of the old cuticle from the body surface, was normal; however, the newly synthesized cuticle was thinner than the cuticle of the control insects. Indeed, chitin content dropped after suppression of LmKnk expression. As seen by transmission electron microscopy, crystalline chitin organization was lost in dsLmKnk-treated insects. In addition, the structure of pore canals, which are lipid transporting routes in the cuticle, was abnormal. Consistently, their content was reduced and, probably by consequence, lipid deposition on the cuticle was decreased after injection of dsLmKnk. Suppression of LmKnk transcript levels rendered L. migratoria more susceptible to each of four selected insecticides including malathion, chlorpyrifos, carbaryl and deltamethrin. Overall, our data show that LmKnk is needed for correct chitin amounts and organization, and their changes ultimately affect cuticular permeability in L. migratoria.

Progress in valorisation of agriculture, aquaculture and shellfish biomass into biochemicals and biomaterials towards sustainable bioeconomy

The recurrent environmental and economic issues associated with the diminution of fossil fuels are the main impetus towards the conversion of agriculture, aquaculture and shellfish biomass and the wastes into alternative commodities in a sustainable approach. In this review, the recent progress on recovering and processing these biomass and waste feedstocks to produce a variety of value-added products via various valorisation technologies, including hydrolysis, extraction, pyrolysis, and chemical modifications are presented, analysed, and discussed. These technologies have gained widespread attention among researchers, industrialists and decision makers alike to provide markets with bio-based chemicals and materials at viable prices, leading to less emissions of CO2 and sustainable management of these resources. In order to echo the thriving research, development and innovation, bioresources and biomass from various origins were reviewed including agro-industrial, herbaceous, aquaculture, shellfish bioresources and microorganisms that possess a high content of starch, cellulose, lignin, lipid and chitin. Additionally, a variety of technologies and processes enabling the conversion of such highly available bioresources is thoroughly analysed, with a special focus on recent studies on designing, optimising and even innovating new processes to produce biochemicals and biomaterials. Despite all these efforts, there is still a need to determine the more cost-effective and efficient technologies to produce bio-based commodities.

True grit: ingestion of small stone particles by hummingbirds in West Mexico

BackgroundGrit is used by birds mainly for grinding hard food items but can also serve a nutritional role as a source of minerals. Ingestion of grit by birds has been documented primarily in species that feed on seeds and invertebrates. Although feeding mainly on nectar and small arthropods, hummingbirds also ingest grit, but why they do so is unclear. We quantified the number of grit particles in the stomachs of six species of hummingbirds during an annual cycle in a seasonal ecosystem of West Mexico.MethodsWe compared the number of grit particles in the stomachs of different hummingbird species (Mexican Violetear Colibri thalassinus, Amethyst-throated Mountaingem Lampornis amethystinus, White-eared Hummingbird Basilinna leucotis, Rivoli’s Hummingbird Eugenes fulgens, Broad-tailed Hummingbird Selasphorus platycercus, and Rufous Hummingbird S. rufus), and between sex and age categories during the different seasons of a year. To determine if grit was used to grind ingested arthropods, we examined the relationships between the number of grit particles, the biomass of arthropods ingested, and their chitin content.ResultsAlthough species did not differ in the number of grit particles in their stomachs, we found that grit was mostly ingested by female individuals, with only one male of one species (Mexican Violetear) presenting grit in its stomach. We also found that female hummingbirds had grit in their stomachs during the rainy and the cold-dry season (June–February) but not during the warm-dry season (March–May). Our analyses revealed no relationship between the number of grit particles and the amount of ingested arthropods and arthropod chitin content. However, high grit consumption was related to wasp ingestion on Mexican Violetears.ConclusionsOur results indicate that grit is used mainly by female hummingbirds. The seasonal variation in the ingestion of grit by female individuals suggests that it can be used to meet mineral requirements related to breeding; however, this topic needs further exploration. Additionally, the use of grit was proportionally higher in juvenile individuals, suggesting it is used for grinding arthropods during a period of fast development.

A combination of cinnamaldehyde and citral greatly alleviates postharvest occurrence of sour rot in citrus fruits without compromising the fruit quality.

One of the most troublesome postharvest diseases of citrus fruits is sour rot, caused by Geotrichum citri-aurantii. Sour rot reduces the shelf life of the fruits leading to massive economic losses. This study investigated the potential for a combination of cinnamaldehyde and citral (CC; 1: 2, v/v) at reducing the incidence of sour rot postharvest and its possible effect on fruit quality. Our findings show that CC could totally inhibit germination of G. citri-aurantii spores, with the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) both being 0.80mL L-1. The combination (CC) acted against G. citri-aurantii by targeting the chitin content of the cell wall. Wax + CC (WCC; 1 × MFC) treatment also showed high efficiency in reducing the incidence of sour rot, which was 40% lower than in the control group by day 8 when all the fruits in the latter were rotten. Apart from vitamin c (Vc) content which was higher in the test group than in the control group, WCC treatment did not have any significant effect on the quality of the citrus fruits, the examined fruit quality parameters being weight loss rate, coloration index, firmness, pH, total soluble solid (TSS) content, Vc content, as well as solid acid ratio. These results indicate that the combination of cinnamaldehyde and citral (CC, 1: 2, v/v) can be used as a natural preservative to alleviate the progress of sour rot in citrus fruits postharvest.

Novel Insights on the Sustainable Wet Mode Fractionation of Black Soldier Fly Larvae (Hermetia illucens) into Lipids, Proteins and Chitin

The black soldier fly larvae (BSFL) is a sustainable ingredient for feed applications, biofuels, composite materials and other biobased products. Processing BSFL to obtain lipid and protein fractions with enhanced functional properties as a suitable replacement for conventional feed ingredients has gained considerable momentum. In this regard, a novel and sustainable wet mode fractionation (WMF) scheme for BSFL was explored. Fresh BSFL were steam blanched and pulped to obtain BSFL juice and juice press cake. Subsequent treatment of BSFL juice employing homogenization or enzyme incubation and further centrifugation resulted in the obtention of four different BSFL fractions (Lipid—LF; Cream—CF; Aqueous—AF; and Solid—SF). Total energy consumption for a batch BSFL (500 g) WMF process was 0.321 kWh. Aqueous and solid fractions were the predominant constituents of BSFL juice. Lauric acid (44.52–49.49%) and linoleic acid (19.12–20.12%) were the primary fatty acids present in BSFL lipids. Lipid hydrolysis was observed in lipids belonging to the solid (free fatty acids > triacylglycerides) and cream fractions. Aqueous fraction proteins (ctrl) displayed superior emulsion stability and foam capacity than other treatments. Juice press cake retained 60% of the total chitin content and the rest, 40%, was found in the solid fraction (ctrl). The material distribution of principal constituents in different fractions of the WMF process and amino acid profile was elucidated. Overall, the versatile WMF process proposed in this study involves simple unit operations to obtain functional ingredients from BSFL, which can be further explored by researchers and industry stakeholders.

Validamycin treatment significantly inhibits the glycometabolism and chitin synthesis in the common cutworm, Spodoptera litura.

Validamycin, as a broadly applied antibiotic, has been used to control rice sheath blight disease. Furthermore, validamycin was considered as an insecticide to control agricultural pests. Insight into the mechanism of validamycin's action on insects can provide molecular targets for the control of agricultural pests. In this study, a toxicological test analysis revealed that Spodoptera litura larval growth and development was significantly inhibited and the pupation rate was significantly reduced with the increase of the concentration of validamycin. According to the NMR-based metabolomic analysis, a total of 15 metabolites involved in glycolysis and tricarboxylic acid cycle (TCA) pathways were identified. Additionally, trehalase activities, glucose and chitin contents were significantly downregulated, but the trehalose content was upregulated after exposure to validamycin. Reverse transcription quantitative PCR analysis revealed that the expression level of genes involved in glycolysis, TCA and chitin synthesis were upregulated after treating with validamycin. Further chitin staining also confirmed that chitin content was downregulated at 12h after validamycin treatment. Our results indicated that validamycin worked via two different molecular mechanisms, one through inhibiting glycometabolism and the other by inhibiting chitin synthesis in S. litura. The information lays a theoretical foundation for further control of S. litura.

Drk1, a Dimorphism Histidine Kinase, Contributes to Morphology, Virulence, and Stress Adaptation in Paracoccidioides brasiliensis

P. brasiliensis is a thermally dimorphic fungus belonging to Paracoccidioides complex, causative of a systemic, endemic mycosis limited to Latin American countries. Signal transduction pathways related to important aspects as surviving, proliferation according to the biological niches are linked to the fungal pathogenicity in many species, but its elucidation in P. brasiliensis remains poorly explored. As Drk1, a hybrid histidine kinase, plays regulators functions in other dimorphic fungi species, mainly in dimorphism and virulence, here we investigated its importance in P. brasilensis. We, therefore generated the respective recombinant protein, anti-PbDrk1 polyclonal antibody and a silenced strain. The Drk1 protein shows a random distribution including cell wall location that change its pattern during osmotic stress condition; moreover the P. brasiliensis treatment with anti-PbDrk1 antibody, which does not modify the fungus’s viability, resulted in decreased virulence in G. mellonella model and reduced interaction with pneumocytes. Down-regulating PbDRK1 yielded phenotypic alterations such as yeast cells with more elongated morphology, virulence attenuation in G. mellonella infection model, lower amount of chitin content, increased resistance to osmotic and cell wall stresses, and also caspofungin, and finally increased sensitivity to itraconazole. These observations highlight the importance of PbDrk1 to P. brasiliensis virulence, stress adaptation, morphology, and cell wall organization, and therefore it an interesting target that could help develop new antifungals.

Caspofungin-resistance in Candida auris is cell wall-dependent phenotype and potential prevention by zinc oxide nanoparticles.

Candida auris developed resistance against caspofungin. Our data indicated that this resistance mechanism is unique because of changes in the genes related to cell wall adhesions. Formulation of caspofungin in ZnO nanoparticles was able to overcome these phenotypic changes.

Colony composition and nutrient analysis of Polyrhachis dives ants, a natural prey of the Chinese pangolin (Manis pentadactyla).

The Chinese pangolin (Manis pentadactyla) is a critically endangered mammal with a highly specialized diet. To enhance nutritional knowledge of its diet, we analyzed the colony composition of a nest of Polyrhachis dives ants, which is the key natural prey in the Chinese pangolin's diet. In addition, we determined the nutrient composition of the total colony compared with adult ants. Nutrients quantified in this study included: crude protein, crude fat, carbohydrate, and amino acids, minerals, and vitamins, as well as formic acid and chitin, which have not been reported in previous diet studies. Our results showed that the colony consisted of adults (82%), pupae (10%), larvae (7%), and eggs (1%) (fresh mass). Both the total colony and adult ants, respectively, contained high concentrations of crude protein (62.97% and 64.68%), chitin (49.25% and 60.40%), crude fat (10.12% and 9.91%) (dry matter basis), and formic acid (2.06% and 3.07%) (fresh mass). This implies that Chinese pangolin might prefer prey with high protein, high chitin, low fat, and low formic acid content. Colony and adult ants differed in chemical composition in many aspects, thus it might be unsuitable to feed Chinese pangolin with only adult ants. Chitin and formic acid may play important roles in the diet and selectivity of Chinese pangolin. This study provides reference information that may be useful for developing better artificial diets with more comprehensive nutrient compositional data to meet the nutritional requirements of the Chinese pangolin under managed feeding programs.

Nuisance mucilage produced by Lindavia intermedia (Bacillariophyceae) in New Zealand lakes

ABSTRACT The invasive centric diatom Lindavia intermedia arrived in New Zealand in recent decades. It produces a pelagic mucilage, which forms an adhesive substance known as lake snow. While determining cell concentrations of L. intermedia is relatively straightforward, methods to estimate mucilage concentration in lake water have not yet been developed. Two methods for lake snow quantification are reported here: a dragged line, or “snow tow,” and in situ filtration. A chemical assay for hexosamine, as an estimate of chitin content, and an atomic absorption method, which measures silicon, were used to measure these components of lake snow. Samples from 4 lakes revealed a correlation between snow tow and filtration data; in principle, the snow tow method (used by municipal authorities) could be calibrated and made quantifiable using the filtration method. Expression of the chitin synthase gene in summer/autumn (but not in winter/spring) correlated with abundance of the chitin component of lake snow, aligning with anecdotal evidence for the timing of its development in lakes. By contrast, cell densities correlated poorly with lake snow abundance. Cell concentrations relative to chitin concentrations were also higher in winter/spring than in summer/autumn across lakes. Dry weight and silicate in lake snow relative to chitin varied by lake and season. The quantification of lake snow and its adhesiveness are important parameters for assessing its nuisance value and fouling characteristics and for developing measures to prevent and remediate its incursion in lakes.

Potensi Limbah Sisik Ikan Sebagai Kitosan dalam Pembuatan Bioplastik

<p><strong>Bioplastics are environmentally friendly plastics derived from natural materials. Bioplastics are easier to decompose when compared to commercial plastics. Bioplastics are generally made from starch contained in plants. But the use of starch as a base material has the disadvantage of producing bioplastics that are not waterproof. Therefore, it is necessary to add chitosan to improve bioplastic characteristics. Chitosan usually comes from the shell of crustacean animals, but it turns out that in fish scales waste, also contains chitosan. Fish scales are a by-product of the process of fish processing. Fish scales are only discarded and not utilized so that they become waste that can pollute the environment. Fish scales have a chitin content that can process into chitosan, which can be useful as an additional ingredient in the manufacture of bioplastics. This review aims to find out the potential of fish scales waste as chitosan in the manufacture of bioplastics. Based on the results of previous research, fish scales have a chitosan content that can use as an additional ingredient in the manufacture of bioplastics. Fish scale chitosan can form bioplastic film with characteristic brownish-yellow film. The addition of fish scale chitosan is also able to improve the water resistance of bioplastic film. Based on the results of the review can be concluded bring fish scales to have the potential as chitosan that can use in the manufacture of bioplastic.</strong></p><p><strong>Keywords –</strong> <em>Bioplastic, Chitosan, Fish Scales.</em></p><p> </p>

Chitin-biocalcium as a novel superior composite for ciprofloxacin removal: Synergism of adsorption and flocculation

The ubiquitous present antibiotics in aquatic environment is attracting increasing concern due to the dual problems of bioaccumulation toxicity and antibiotic resistance. In this study, a low-cost chitin-biocalcium (CC) composite was developed by a facile alkali activation process from shell waste for typical antibiotics ciprofloxacin (CIP) removal. Response surface methodology (RSM) was utilized to optimize synthesis methodology. The optimized CC products featured superior CIP removal capacity of 2432 mg/g at 25 °C (adsorption combined with flocculation), rapid adsorption kinetics, high removal efficiency (95.58%) and wide pH adaptability (under pH range 4.0–10.0). The functional groups in chitin and high content of biocalcium (Ca2+) endowed CC abundant active sites. The kinetic experimental data was fitted well by pseudo-second-order and intraparticle diffusion model at different concentrations, revealing the removal was controlled by chemisorption and mass transport step. From the macroscopic aspect, flocs were produced with the increase of CIP concentration during the reaction, adsorption combined with flocculation were related to the CIP removal. From the microcosmic aspect, the superior removal performance was attributed to cation bridging, cation complexation among biocalcium-CIP and hydrogen bond between functional groups of chitin and CIP.

Comparing black soldier fly (Hermetia illucens) larvae versus prepupae in the diets of largemouth bass, Micropterus salmoides: Effects on their growth, biochemical composition, histopathology, and gene expression

An 8-week feeding trial was performed to compare the supplementation of full-fat black soldier fly, Hermetia illucens, larvae (BSFL) versus pre-pupae (BSFP) in the diets of largemouth bass, Micropterus salmoides, juveniles. Both BSFL and BSFP were produced in the laboratory from the same batch and ingredients although BSFP tended to have higher protein and amino acid content. Four isonitrogenous and isolipidic diets were formulated including a fishmeal-based control diet (D1), soybean meal-based diet (D2) and soybean meal-based diets with either BSFL (D3) or BSFP (D4) at 4.2% contributing protein (or 11.90 and 9.83%, respectively). Survival, growth, feed intake, muscle/liver fatty acid composition/mineral composition, hepatic/intestinal expression of growth (insulin-like growth factor ‘IGF-I’, growth hormone ‘GH’), lipid metabolism (cholesterol 7 alpha-hydroxylase ‘CYP7A1’, fatty acid synthase ‘FASN’), antioxidant sentinals (superoxide dismutase ‘SOD’), inflammatory cytokines (tumor necrosis factor-α ‘TNF-α’, transforming growth factor- β1 ‘TGF-β1’) representative genes as well as liver/intestinal histopathology were determined. Although survival was similar among treatments, fish growth pattern was D1 > D2 > D3 > D4, with each treatment significantly different than the others. Feed intake was significantly lower in the D4 treatment. Liver and intestinal histopathology were similar between D1 and D2, but intestinal villi were less tightly packed in fish fed D3 or D4 compared to those in the D1 and D2 treatments. In the D4 treatment, liver histology revealed inflammation and necrosis in a third of the fish sampled, while the intestinal villi were significantly shorter and wider, respectively. Nevertheless, for most of the hepatic genes tested, the expression in fish fed D3 or D4 generally mirrored those of the control diet. Although the nutritional value of BSFL and BSFP depends on their diet, this study clearly demonstrates that BSFL is better for M. salmoides compared to BSFP, which may be related to the high chitin content of the BSFP.

On the nitrogen content and a robust nitrogen-to-protein conversion factor of black soldier fly larvae (Hermetia illucens).

Currently, a broad discussion exists in the literature regarding insect protein analysis. At its core, main difficulties and uncertainties are the inconsistent use of analysis methods and nitrogen-to-protein conversion (kP) factors. While the Kjeldahl and Dumas methods are both used in the literature, their result represents inherently different nitrogen fractions. Thus far, no correlation between them is established for insect matrices, which is a major uncertainty. Although much effort has been made towards more accurate kP factors, calculation of these was based on merely one sample while the chemical composition varies depending on rearing conditions. Using a broad variation in black soldier fly (BSF) larvae samples in the present study, a correlation between Kjeldahl and Dumas and a robust kP factor have been established. Moreover, the nitrogen distribution of BSF samples was also assessed after accurate chitin analyses. A highly significant linear correlation existed between the results of Kjeldahl and Dumas (slope, 1.009; intercept, - 0.008; R2, 0.9997). Consequently, both methods were deemed interchangeable for BSF larvae. Using amino acid data, a practical, more accurate and robust kP factor of 4.43 was obtained. Concerning the chitin content, the average of all BSF larvae samples was 5.95 ± 0.86g N-acetylglucosamine/100g dry matter and no correlation with the kP factor was observed. Regarding the nitrogen distribution of the samples, it was found that the contribution of nitrogenous compounds other than protein and chitin is not only high but also prone to variation (12-30% of the total nitrogen content).

Regulation of conidiation, polarity growth, and pathogenicity by MrSte12 transcription factor in entomopathogenic fungus, Metarhizium rileyi

Metarhizium rileyi, a well-known filamentous biocontrol fungus, is the main pathogen of numerous field pests, especially noctuid pests. To explore the potential factors involved in the fungal pathogenicity, MrSte12, an important and conserved functional transcription factor in mitogen-activated protein kinase pathway was carried out by functional analysis. Homologous recombination was used to disrupt the MrSte12 gene in M. rileyi. The deletant fungal strain exhibited malformed hyphae and impaired conidiogenesis, and conidia could not be collected from △MrSte12 in vitro towards SMAY medium. Although conidia could be collected again supplemented with KCl within SMAY medium, the conidial germination, growth and stress tolerance were much weaker compared with that in WT. Additionally, △MrSte12 showed a dramatic reduction in virulence in intra-hemolymph injections and no pathogenicity in topical inoculations against noctuid pests, which is due to the failure of appressorium formation. Moreover, the content of chitin and β-1, 3-glucan in cell wall significantly reduced in mutant conidia. These results indicate that the MrSte12 gene markedly contributes to invasive growth and conidiation, as well as the major pathogenicity in M. rileyi.

Full-Length Transcriptome of Thalassiosiraweissflogii as a Reference Resource and Mining of Chitin-Related Genes.

β-Chitin produced by diatoms is expected to have significant economic and ecological value due to its structure, which consists of parallel chains of chitin, its properties and the high abundance of diatoms. Nevertheless, few studies have functionally characterised chitin-related genes in diatoms owing to the lack of omics-based information. In this study, we first compared the chitin content of three representative Thalassiosira species. Cell wall glycosidic linkage analysis and chitin/chitosan staining assays showed that Thalassiosira weissflogii was an appropriate candidate chitin producer. A full-length (FL) transcriptome of T. weissflogii was obtained via PacBio sequencing. In total, the FL transcriptome comprised 23,362 annotated unigenes, 710 long non-coding RNAs (lncRNAs), 363 transcription factors (TFs), 3113 alternative splicing (AS) events and 3295 simple sequence repeats (SSRs). More specifically, 234 genes related to chitin metabolism were identified and the complete biosynthetic pathways of chitin and chitosan were explored. The information presented here will facilitate T. weissflogii molecular research and the exploitation of β-chitin-derived high-value enzymes and products.

Efficient conversion of carbohydrates and biomass into furan compounds by chitin/Ag co-modified H3PW12O40 catalysts

The development of heterogeneously functional catalysts is of great significance in selective catalysis for biomass valorization. Herein, we report for the first time the applicability of chitin/Ag co-modified H3PW12O40 composites (Chx-AgPW) as catalysts for producing valuable furans from carbohydrates and biomass. The as-prepared Ch15-AgPW catalyst exhibited the best catalytic performance, due to the dual Brǿnsted-Lewis acidity and appropriate chitin content. When the amount of Ch15-AgPW catalyst was 0.25 mmol, an excellent 5-hydroxymethylfurfural (HMF) yield of 78.3% could be achieved at 150 °C for 3 h with nearly 100% glucose conversion in the H2O/MIBK (VH2O:MIBK = 4:6) solvent system. Furthermore, high-yield HMF could also be obtained from other carbohydrates such as fructose (85.3%), sucrose (72.3%), cellobiose (65.6%), starch (52.7%) and inulin (43.5%). Additionally, corn stover, rice straw and sugarcane bagasse under typical reaction conditions simultaneously produced furfural and HMF in yields of 64.6%–72.2% and 18.5%–25.6%, respectively. Combined with the characterization, mechanism study demonstrated that the surface functional groups in chitin were conductive to rapid absorption of the substrates; the Brǿnsted acid sites from heteropoly anion (H2[PW12O40]-) promoted the initial depolymerization of biomass and the final dehydration to furans; the introduction of Ag+ favored the isomerization of intermediates. After reaction finished, the Ch15-AgPW catalyst could be easily recovered by filtration and effectively reused at least eight cycles without substantial loss in catalytic activity. This work provides a novel strategy to synthesize stable heterogeneous catalysts with tunable acidity for producing bio-based fuels and chemicals from renewable resources.