Advances in biotin biosynthesis and biotechnological production in microorganisms.

Biotin, also known as vitamin H or B7, acts as a crucial cofactor in the central metabolism processes of fatty acids, amino acids, and carbohydrates. Biotin has important applications in food additives, biomedicine, and other fields. While the ability to synthesize biotin de novo is confined to microorganisms and plants, humans and animals require substantial daily intake, primarily through dietary sources and intestinal microflora. Currently, chemical synthesis stands as the primary method for commercial biotin production, although microbial biotin production offers an environmentally sustainable alternative with promising prospects. This review presents a comprehensive overview of the pathways involved in de novo biotin synthesis in various species of microbes and insights into its regulatory and transport systems. Furthermore, diverse strategies are discussed to improve the biotin production here, including mutation breeding, rational metabolic engineering design, artificial genetic modification, and process optimization. The review also presents the potential strategies for addressing current challenges for industrial-scale bioproduction of biotin in the future. This review is very helpful for exploring efficient and sustainable strategies for large-scale biotin production.

Biological synthesis of nicotinamide mononucleotide.

Nicotinamide mononucleotide (NMN) or Nicotinamide-1-ium-1-ß-D-ribofuranoside 5'-phosphate is a nucleotide that can be converted into nicotinamide adenine dinucleotide (NAD) in human cells. NMN has recently attracted great attention because of its potential as an anti-aging drug, leading to great efforts for its effective manufacture. The chemical synthesis of NMN is a challenging task since it is an isomeric compound with a complicated structure. The majority of biological synthetic routes for NMN is through the intermediate phosphoribosyl diphosphate (PRPP), which is further converted to NMN by nicotinamide phosphoribosyltransferase (Nampt). There are various routes for the synthesis of PRPP from simple starting materials such as ribose, adenosine, and xylose, but all of these require the expensive phosphate donor adenosine triphosphate (ATP). Thus, an ATP regeneration system can be included, leading to diminished ATP consumption during the catalytic process. The regulations of enzymes that are not directly involved in the synthesis of NMN are also critical for the production of NMN. The aim of this review is to present an overview of the biological production of NMN with respect to the critical enzymes, reaction conditions, and productivity.

Quantitative detection method of Enterocytozoon hepatopenaei using TaqMan probe real-time PCR.

A TaqMan probe and a pair of specific primers were selected from the small subunit ribosomal DNA (SSU rDNA) sequence of Enterocytozoon hepatopenaei (EHP); this real-time PCR assay was developed and optimized. It showed a good linearity in detecting standards of EHP SSU rDNA fragments from 4 × 102 to 4 × 108 copies/reaction using the established method. The detection limit of the qPCR method was as low as 4 × 101 copies per reaction, which was higher than the conventional PCR and SYBR Green I-based EHP qPCR reported. Using the qPCR assay, EHP was detected in four batches of slow-growing Penaeus vannamei specimens collected from Tianjin and Zhejiang Province in China was detected using qPCR. The results showed that all the hepatopancreas from the slow-growing P. vannamei specimens were detected as EHP-positive. EHP copies of hepatopancreas in some batches had a negative correlation with the body mass index (BMI) of shrimps; however, not all batches of specimens had this negative correlation between EHP copies of hepatopancreas and BMI. This qPCR technique is sensitive, specific and easy to perform (96 tests in <3 h), which provides technical support for the detection and prevention of EHP.

Characterization of a new member of Iridoviridae, Shrimp hemocyte iridescent virus (SHIV), found in white leg shrimp (Litopenaeus vannamei).

A newly discovered iridescent virus that causes severe disease and high mortality in farmed Litopenaeus vannamei in Zhejiang, China, has been verified and temporarily specified as shrimp hemocyte iridescent virus (SHIV). Histopathological examination revealed basophilic inclusions and pyknosis in hematopoietic tissue and hemocytes in gills, hepatopancreas, periopods and muscle. Using viral metagenomics sequencing, we obtained partial sequences annotated as potential iridoviridae. Phylogenetic analyses using amino acid sequences of major capsid protein (MCP) and ATPase revealed that it is a new iridescent virus but does not belong to the five known genera of Iridoviridae. Transmission electron microscopy showed that the virus exhibited a typical icosahedral structure with a mean diameter of 158.6 ± 12.5 nm (n = 30)(v-v) and 143.6 ± 10.8 nm (n = 30)(f-f), and an 85.8 ± 6.0 nm (n = 30) nucleoid. Challenge tests of L. vannamei via intermuscular injection, per os and reverse gavage all exhibited 100% cumulative mortality rates. The in situ hybridization showed that hemopoietic tissue, gills, and hepatopancreatic sinus were the positively reacting tissues. Additionally, a specific nested PCR assay was developed. PCR results revealed that L. vannamei, Fenneropenaeus chinensis, and Macrobrachium rosenbergii were SHIV-positive, indicating a new threat existing in the shrimp farming industry in China.