Zhi Luo

Bio: Zhi Luo is an academic researcher from Huazhong Agricultural University. The author has contributed to research in topics: Phytase & Commercial fish feed. The author has an hindex of 1, co-authored 1 publications receiving 291 citations.

BOARD-INVITED REVIEW: opportunities and challenges in using exogenous enzymes to improve nonruminant animal production.

Abstract: Diets fed to nonruminant animals are composed mainly of feed ingredients of plant origin. A variety of antinutritional factors such as phytin, nonstarch polysaccharides, and protease inhibitors may be present in these feed ingredients, which could limit nutrients that may be utilized by animals fed such diets. The primary nutrient utilization-limiting effect of phytin arises from the binding of 6 phosphate groups, thus making the P unavailable to the animal. The negative charges allow for formation of insoluble phytin-metal complexes with many divalent cations. Furthermore, phytin and protein can form binary complexes through electrostatic links of its charged phosphate groups with either the free amino group on AA on proteins or via formation of ternary complexes of phytin, Ca(2+), and protein. The form and extent of de novo formation of binary and ternary complexes of phytin and protein are likely to be important variables that influence the effectiveness of nutrient hydrolysis in plant-based diets. Nonstarch polysacharides reduce effective energy and nutrient utilization by nonruminant animals because of a lack of the enzymes needed for breaking down the complex cell wall structure that encapsulate other nutrients. Enzymes are used in nonruminant animal production to promote growth and efficiency of nutrient utilization and reduce nutrient excretion. The enzymes used include those that target phytin and nonstarch polysaccharides. Phytase improves growth and enhances P utilization, but positive effects on other nutrients are not always observed. Nonstarch polysaccharide-hydrolyzing enzymes are less consistent in their effects on growth and nutrient utilization, although they show promise and it is imperative to closely match both types and amounts of nonstarch polysaccharides with appropriate enzyme for beneficial effects. When used together with phytase, nonstarch polysaccharide-hydrolyzing enzymes may increase the accessibility of phytase to phytin encapsulated in cell walls. The future of enzymes in nonruminant animal production is promising and will likely include an understanding of the role of enzyme supplementation in promoting health as well as how enzymes may modulate gene functions. This review is an attempt to summarize current thinking in this area, provide some clarity in nomenclature and mechanisms, and suggest opportunities for expanded exploitation of this unique biotechnology.

Phytate: impact on environment and human nutrition. A challenge for molecular breeding

Abstract: Phytic acid (PA) is the primary storage compound of phosphorus in seeds accounting for up to 80% of the total seed phosphorus and contributing as much as 1.5% to the seed dry weight. The negatively charged phosphate in PA strongly binds to metallic cations of Ca, Fe, K, Mg, Mn and Zn making them insoluble and thus unavailable as nutritional factors. Phytate mainly accumulates in protein storage vacuoles as globoids, predominantly located in the aleurone layer (wheat, barley and rice) or in the embryo (maize). During germination, phytate is hydrolysed by endogenous phytase(s) and other phosphatases to release phosphate, inositol and micronutrients to support the emerging seedling. PA and its derivatives are also implicated in RNA export, DNA repair, signalling, endocytosis and cell vesicular trafficking. Our recent studies on purification of phytate globoids, their mineral composition and dephytinization by wheat phytase will be discussed. Biochemical data for purified and characterized phytases isolated from more than 23 plant species are presented, the dephosphorylation pathways of phytic acid by different classes of phytases are compared, and the application of phytase in food and feed is discussed.

Environmental impact of aquaculture and countermeasures to aquaculture pollution in China

Abstract: Goal, Scope and Background. Aquaculture activities are well known to be the major contributor to the increasing level of organic waste and toxic compounds in the aquaculture industry. Along with the development of intensive aquaculture in China, concerns are evoked about the possible effects of everincreasing aquaculture waste both on productivity inside the aquaculture system and on the ambient aquatic ecosystem. Therefore, it is apparent that appropriate waste treatment processes are needed for sustaining aquaculture development. This review aims at identifying the current status of aquaculture and aquaculture waste production in China. Main Features. China is the world's largest fishery nation in terms of total seafood production volume, a position it has maintained continuously since 1990. Freshwater aquaculture is a major part of the Chinese fishery industry. Marine aquaculture in China consists of both land-based and offshore aquaculture, with the latter mostly operated in shallow seas, mud flats and protected bays. The environmental impacts of aquaculture are also striking. Results. Case studies on pollution hot spots caused by aquaculture have been introduced. The quality and quantity of waste from aquaculture depends mainly on culture system characteristics and the choice of species, but also on feed quality and management. Wastewater without treatment, if continuously discharged into the aquatic environment, could result in remarkable elevation of the total organic matter contents and cause considerable economy lost. Waste treatments can be mainly classified into three categories: physical, chemical and biological methods. Discussion. The environmental impacts of different aquaculture species are not the same. New waste treatments are introduced as references for the potential development of the waste treatment system in China. The most appropriate waste treatment system for each site should be selected according to the sites'

Phytase in non-ruminant animal nutrition: a critical review on phytase activities in the gastrointestinal tract and influencing factors.

Abstract: This review focuses on phytase functionality in the digestive tract of farmed non-ruminant animals and the factors influencing in vivo phytase enzyme activity. In pigs, feed phytase is mainly active in the stomach and upper part of the small intestine, and added phytase activity is not recovered in the ileum. In poultry, feed phytase activities are mainly found in the upper part of the digestive tract, including the crop, proventriculus and gizzard. For fish with a stomach, phytase activities are mainly in the stomach. Many factors can influence the efficiency of feed phytase in the gastrointestinal tract, and they can be divided into three main groups: (i) phytase related; (ii) dietary related and (iii) animal related. Phytase-related factors include type of phytase (e.g. 3- or 6-phytase; bacterial or fungal phytase origin), the pH optimum and the resistance of phytase to endogenous protease. Dietary-related factors are mainly associated with dietary phytate content, feed ingredient composition and feed processing, and total P, Ca and Na content. Animal-related factors include species, gender and age of animals. To eliminate the antinutritional effects of phytate (IP6), it needs to be hydrolyzed as quickly as possible by phytase in the upper part of the digestive tract. A phytase that works over a wide range of pH values and is active in the stomach and upper intestine (along with several other characteristics and in addition to being refractory to endogenous enzymes) would be ideal. © 2014 The Authors. Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Phytate and phytase in fish nutrition

Abstract: Phytate formed during maturation of plant seeds and grains is a common constituent of plant-derived fish feed. Phytate-bound phosphorus (P) is not available to gastric or agastric fish. A major concern about the presence of phytate in the aquafeed is its negative effect on growth performance, nutrient and energy utilization, and mineral uptake. Bound phytate-P, can be effectively converted to available-P by phytase. During the last decade, phytase has been used by aqua feed industries to enhance the growth performance, nutrient utilization and bioavailability of macro and micro minerals in fish and also to reduce the P pollution into the aquatic environment. Phytase activity is highly dependent on the pH of the fish gut. Unlike mammals, fish are either gastric or agastric, and hence, the action of dietary phytase varies from species to species. In comparison to poultry and swine production, the use of phytase in fish feed is still in an unproven stage. This review discusses effects of phytate on fish, dephytinisation processes, phytase and pathway for phytate degradation, phytase production systems, mode of phytase application, bioefficacy of phytase, effects of phytase on growth performance, nutrient utilization and aquatic environment pollution, and optimum dosage of phytase in fish diets.