Efficient production of inositol from glucose via a tri-enzymatic cascade pathway

Metabolic engineering of Kluyveromyces marxianus to produce myo-inositol from starch

To efficiently produce myo-inositol from glucose, the PGI1, ZWF1, ITR2, and MIOX5 genes in Kluyveromyces marxianus were knocked out to block glucose metabolism via the Embden-Meyerhof-Parnas (EMP) and pentose phosphate pathways (PPP), prevent myo-inositol oxidative degradation. The metabolically engineered KM-JC4 strain, introduced with myo-inositol synthesis genes, produced 80.7 g/L in a 5 L bioreactor using glucose and glycerol as carbon sources. Subsequently, the starch-fermenting and inositol-producing strain KM-JC5 was constructed by co-expressing BadGlA, an α-glucoamylase from Blastobotrys adeninivorans with high ability to release glucose from soluble starch, and the myo-inositol synthesis enzymes. Using 5% soluble starch and liquefied starch, the myo-inositol yields reached 32.2 g/L and 40.6 g/L, with the starch-to-myo-inositol conversion rates of 64.4% and 81.1%, respectively. This study provides an effective strategy for bioproduction by balancing glycolysis and PPP metabolism in yeast, and the metabolically engineered strain represents a promising platform for inositol production.

Synergistic utilization of glucose and xylose for the myo-inositol biosynthesis in recombinant Escherichia coli BL21

Myo-inositol is an active sugar alcohol which has important physiological functions. In this study, an engineered strain that could simultaneously utilize glucose and xylose to produce myo-inositol was constructed, and its fermentation performance was determined. Firstly, the ptsG gene was deleted to make E. coli BL21 capable of utilizing glucose and xylose simultaneously as mixed carbon source. Galp and glk genes were introduced to promote the glucose absorption after ptsG knockout. Secondly, the ino1 gene from Saccharomyces cerevisiae SC288 was introduced and the suhB gene was overexpressed to construct the complete biosynthetic pathway of myo-inositol in E. coli BL21. Ultimately, when 20 g/L glucose and xylose with a ratio of 3:2 were used as the mixed carbon source, the consumption rate of the total sugar was the fastest, and the yield of myo-inositol was 0.63 g/L in 50 mL/250 mL culture system. When the fermentation system was expanded to 1 L shake flask, the yield of myo-inositol was 0.69 g/L. This study contributes to the production of myo-inositol with mixed sugar as the carbon source.

Exploring the potential of myo-inositol in thyroid disease management: focus on thyroid cancer diagnosis and therapy

Thyroid cancer (TC) is a malignancy that is increasing in prevalence on a global scale, necessitating the development of innovative approaches for both diagnosis and treatment. Myo-inositol (MI) plays a crucial role in a wide range of physiological and pathological functions within human cells. To date, studies have investigated the function of MI in thyroid physiology as well as its potential therapeutic benefits for hypothyroidism and autoimmune thyroiditis. However, research in the field of TC is very restricted. Metabolomics studies have highlighted the promising diagnostic capabilities of MI, recognizing it as a metabolic biomarker for identifying thyroid tumors. Furthermore, MI can influence therapeutic characteristics by modulating key cellular pathways involved in TC. This review evaluates the potential application of MI as a naturally occurring compound in the management of thyroid diseases, including hypothyroidism, autoimmune thyroiditis, and especially TC. The limited number of studies conducted in the field of TC emphasizes the critical need for future research to comprehend the multifaceted role of MI in TC. A significant amount of research and clinical trials is necessary to understand the role of MI in the pathology of TC, its diagnostic and therapeutic potential, and to pave the way for personalized medicine strategies in managing this intricate disease.

One-pot sustainable synthesis of glucosylglycerate from starch and glycerol through artificial in vitro enzymatic cascade

Glucosylglycerate (R-2-O-α-D-glucopyranosyl-glycerate, GG) is a negatively charged compatible solution with versatile functions. Here, an artificial in vitro enzymatic cascade was designed to feasibly and sustainably produce GG from affordable starch and glycerol. First, Spirochaeta thermophila glucosylglycerate phosphorylase (GGP) was carefully selected because of its excellent heterologous expression, specific activity, and thermostability. The optimized two-enzyme cascade, consisting of alpha-glucan phosphorylase (αGP) and GGP, achieved a remarkable 81 % conversion rate from maltodextrin and D-glycerate. Scaling up this cascade resulted in a practical concentration of 58 g/L GG with a 62 % conversion rate based on the added D-glycerate. Additionally, the production of GG from inexpensive starch and glycerol in one-pot using artificial four-enzyme cascade was successfully implemented, which integrates alditol oxidase and catalase with αGP and GGP. Collectively, this sustainable enzymatic cascade demonstrates the feasibility of the practical synthesis of GG and has the potential to produce other glycosides using the phosphorylase-and-phosphorylase paradigm.

Turning waste into treasure: Biosynthesis of value-added 2-O-α-glucosyl glycerol and d-allulose from waste cane molasses through an in vitro synthetic biology platform

The efficient and economical conversion of agricultural waste into glycosides and rare sugars is challenging. Herein, an in vitro synthetic bienzyme system consisting of sucrose phosphorylase and d-allulose 3-epimerase was constructed to produce 2-O-α-glucosyl glycerol and d-allulose from cane molasses. Lactic acid in the cane molasses significantly induced sucrose phosphorylase to hydrolyze sucrose instead of glycosylation. Notably, lactic acid significantly inhibited the catalytic performance of d-allulose 3-epimerase only in the presence of Na+ and K+, with an inhibition rate of 75%. After removing lactic acid and metal ions, 116 g/L 2-O-α-glucosyl glycerol and 51 g/L d-allulose were synthesized from 500 mM sucrose in the treated cane molasses with a sucrose consumption rate of 97%. Our findings offer an economically efficient and environmentally friendly pathway for the industrial production of glycosides and rare sugars from food industry waste.

Multidimensional engineering of Escherichia coli for efficient biosynthesis of cis-3-hydroxypipecolic acid

Cis-3-hydroxypipecolic acid (cis-3-HyPip) is the crucial part of many alkaloids and drugs. However, its bio-based industrial production remains challenging. Here, lysine cyclodeaminase from Streptomyces malaysiensis (SmLCD) and pipecolic acid hydroxylase from Streptomyces sp. L-49973 (StGetF) were screened to achieve the conversion of L-lysine to cis-3-HyPip. Considering the high-cost of cofactors, NAD(P)H oxidase from Lactobacillus sanfranciscensis (LsNox) was further overexpressed in chassis strain Escherichia coli W3110 ΔsucCD (α-ketoglutarate-producing strain) to construct the NAD⁺ regeneration system, thus realizing the bioconversion of cis-3-HyPip from low-cost substrate L-lysine without NAD⁺ and α-ketoglutarate addition. To further accelerate the transmission efficiency of cis-3-HyPip biosynthetic pathway, multiple-enzyme expression optimization and transporter dynamic regulation via promoter engineering were conducted. Through fermentation optimization, the final engineered strain HP-13 generated 78.4 g/L cis-3-HyPip with 78.9% conversion in a 5-L fermenter, representing the highest production level achieved so far. These strategies described herein show promising potentials for large-scale production of cis-3-HyPip.