Nonphytate Phosphorus Requirement and Efficacy of a Genetically Engineered Yeast Phytase for Yellow Broilers at 22- to 42-d-Old Age

An experiment was conducted to investigate the requirement of nonphytate phosphorus（nPP） and efficacy of a genetically engineered yeast phytase（PHY A） for Lingnan yellow broilers from 22-to 42-d-old age.A total of 1 320 1-d-old male chicks were randomly divided into 11 dietary treatment groups,which consisted of 4 replicate floor pens with 30 birds per pen.The control group（treatment 1） was fed with basal diet of nPP 0.08% without dicalcium phosphate or phytase supplementation.Dietary levels of nPP were 0.16,0.24,0.32,0.40,0.48,and 0.56%,respectively,for treatments 2 to 7,through addition of dicalcium phosphate（chemistry grade） to the basal diet.Diets of treatments 8 to 11 were supplemented with PHY A at 200,400 and 600 U kg-1,a commercial phytase product（PHY B） at 400 U kg-1 level,respectively.The birds in 0.32-0.56% nPP groups gained more than those of the other groups（P0.05）.The nPP supplementation significantly improved feed intake（P0.05）.The feed gain ratio was significantly decreased by 0.40% nPP diet compared to the control birds（P0.05）.The level of 0.48% nPP was required for optimum tibia development.The additions of PHY A at 400 and 600 U kg-1 level and PHY B all significantly improved ADG（P0.05）,ADFI（P0.05）,and dry defatted tibia weight（P0.05）.Similarly,the percentage of tibia ash was increased by 600 U kg-1 PHY A supplementation（P0.05）.The requirement of nPP for maximal ADG and highest percentage tibia ash both was 0.40%.The phosphorus equivalency value of PHY A was estimated as 685 U kg-1 for male yellow broilers of 22-to 42-d-old age.

Identification of the cytochrome P450s responsible for the biosynthesis of two types of aporphine alkaloids and their de novo biosynthesis in yeast

Aporphine alkaloids have diverse pharmacological activities;however,our understanding of their biosynthesis is relatively limited.Previous studies have classified aporphine alkaloids into two categories based on the configuration and number of substituents of the D-ring and have proposed preliminary biosynthetic pathways for each category.In this study,we identified two specific cytochrome P450 enzymes(CYP80G6 and CYP80Q5)with distinct activities toward(S)-configured and(R)-configured substrates from the herbaceous perennial vine Stephania tetrandra,shedding light on the biosynthetic mechanisms and stereochemical features of these two aporphine alkaloid categories.Additionally,we characterized two CYP719C enzymes(CYP719C3 and CYP719C4)that catalyzed the formation of the methylenedioxy bridge,an essential pharmacophoric group,on the A-and D-rings,respectively,of aporphine alkaloids.Leveraging the functional characterization of these crucial cytochrome P450 enzymes,we reconstructed the biosynthetic pathways for the two types of aporphine alkaloids in budding yeast(Saccharomyces cerevisiae)for the de novo production of compounds such as(R)-glaziovine,(S)-glaziovine,and magnoflorine.This study provides key insight into the biosynthesis of aporphine alkaloids and lays a foundation for producing these valuable compounds through synthetic biology.

Advances in engineering methylotrophic yeast for biosynthesis of valuable chemicals from methanol

Methylotrophic yeasts and bacteria, which can use methanol as carbon and energy source, have beenwildly used as microbial cell factories for biomanufacturing. Due to their robustness in industrial harshconditions, methylotrophic yeasts such as Pichia pastoris have been explored as a cell factory forproduction of proteins and high-value chemicals. Methanol utilization pathway （MUT） is highlyregulated for efficient methanol utilization, and the downstream pathways need extensively constructedand optimized toward target metabolite biosynthesis. Here, we present an overview of methanolmetabolism and regulation in methylotrophic yeasts, among which we focus on the regulation of keygenes involved in methanol metabolism. Besides, the recent progresses in construction and optimizationof downstream biosynthetic pathways for production of high value chemicals, such as polyketides, fattyacids and isoprenoids, are further summarized. Finally, we discuss the current challenges and feasiblestrategies toward constructing efficient methylotrophic cell factories may promote wide applications inthe future.