Analysis of German cockroach (Blattella germanica) expressed sequence tags

Edible insects as ingredients in food products: nutrition, functional properties, allergenicity of insect proteins, and processing modifications

Edible insect products contain high-quality protein and other nutrients, including minerals and fatty acids. The consumption of insect food products is considered a future trend and a potential strategy that could greatly contribute to meeting food needs worldwide. However, insect proteins have the potential to be allergenic to insect consumers. In this review, the nutritional value and allergy risk of insect-derived foods, and the immune responses elicited by insect allergens are summarized and discussed. Tropomyosin and arginine kinase are the most important and widely known insect allergens, which induce Th2-biased immune responses and reduced the activity of CD4+T regulatory cells. Besides, food processing methods have been effectively improving the nutrients and characteristics of insect products. However, limited reviews systematically address the immune reactions to allergens present in edible insect proteins following treatment with food processing technologies. The conventional/novel food processing techniques and recent advances in reducing the allergenicity of insect proteins are discussed in this review, focusing on the structural changes of allergens and immune regulation.

Midgut Transcriptome of the Cockroach Periplaneta americana and Its Microbiota: Digestion, Detoxification and Oxidative Stress Response

The cockroach, Periplaneta americana, is an obnoxious and notorious pest of the world, with a strong ability to adapt to a variety of complex environments. However, the molecular mechanism of this adaptability is mostly unknown. In this study, the genes and microbiota composition associated with the adaptation mechanism were studied by analyzing the transcriptome and 16S rDNA pyrosequencing of the P. americana midgut, respectively. Midgut transcriptome analysis identified 82,905 unigenes, among which 64 genes putatively involved in digestion (11 genes), detoxification (37 genes) and oxidative stress response (16 genes) were found. Evaluation of gene expression following treatment with cycloxaprid further revealed that the selected genes (CYP6J1, CYP4C1, CYP6K1, Delta GST, alpha-amylase, beta-glucosidase and aminopeptidase) were upregulated at least 2.0-fold at the transcriptional level, and four genes were upregulated more than 10.0-fold. An interesting finding was that three digestive enzymes positively responded to cycloxaprid application. Tissue expression profiles further showed that most of the selected genes were midgut-biased, with the exception of CYP6K1. The midgut microbiota composition was obtained via 16S rDNA pyrosequencing and was found to be mainly dominated by organisms from the Firmicutes phylum, among which Clostridiales, Lactobacillales and Burkholderiales were the main orders which might assist the host in the food digestion or detoxification of noxious compounds. The preponderant species, Clostridium cellulovorans, was previously reported to degrade lignocellulose efficiently in insects. The abundance of genes involved in digestion, detoxification and response to oxidative stress, and the diversity of microbiota in the midgut might provide P. americana high capacity to adapt to complex environments.