Supplementation in mushroom crops and its impact on yield and quality

Carrasco et al. AMB Expr (2018) 8:146 https://doi.org/10.1186/s13568-018-0678-0 Open Access MINI-REVIEW Supplementation in mushroom crops and its impact on yield and quality Jaime Carrasco1* , Diego C. Zied2, Jose E. Pardo3, Gail M. Preston1 and Arturo Pardo‑Giménez4 Abstract Mushroom supplementation is an agronomic process which consists of the application of nutritional amendments to the substrates employed for mushroom cultivation. Different nitrogen and carbohydrate rich supplements have been evaluated in crops with a substantial impact on mushroom yield and quality; however, there is still controversy regarding the nutritional requirements of mushrooms and the necessity for the development of new commercial additives. The addition of external nutrients increases the productivity of some low-yielding mushroom varieties, and therefore is a useful tool for the industry to introduce new commercially viable varieties. Spent mushroom compost is a waste material that could feasibly be recycled as a substrate to support a new commercially viable crop cycle when amended with supplements. On the other hand, a new line of research based on the use of mushroom growth promoting microorganisms is rising above the horizon to supplement the native microbiota, which appears to cover nutritional deficiencies. Several supplements employed for the cultivated mushrooms and their agronomic potential in terms of yield and quality are reviewed in this paper as a useful guide to evaluate the nutritional requirements of the crop and to design new formulas for commercial supplementation. Keywords: Substrate, Mushroom cultivation, Nutrition, Agronomy, Yield, Quality Introduction Most of the cultivated species of mushrooms belong to the phylum Basidiomycota, although some Ascomycota such as members from the genera Morchella or Tuber have also been successfully cultivated and commercially exploited (Rubini et al. 2014; Liu et al. 2017). Unlike plants, mushrooms are heterotrophic organisms which require external nutrients to grow; the vegetative mycelium (hypha network) supplies nutrients for the growth of basidiomes (reproductive stage) (Taylor and Ellison 2010). Mushrooms produce a number of enzymes including lignin-degrading enzymes (laccases, lignin peroxidases, manganese peroxidases, arylalcohol oxidase, aryl-alcohol dehydrogenases or quinone reductases), and hemicellulose and cellulose-degrading enzymes (xylanase, cellulases or cellobiose dehydrogenase), to facilitate the degradation of lignocellulosic substrates (Sánchez 2009; Kabel et al. 2017; Vos et al. 2017). Furthermore, mushrooms require oxygen and a specific pH in order to develop a normal metabolism and to grow properly. C and N are the two main macronutrients required by fungi for structural and energy requirements; P, K and Mg are also considered macronutrients for mushrooms, in addition, trace elements such as Fe, Se, Zn, Mn, Cu and Mo appear to be needed for diverse functions (Chang and Miles 2004). The initial phase of mushroom production consists of a solid fermentation process. From spawning, the vegetative mycelium grows under controlled environment and aseptic conditions to colonize the mass of substrate before fructifying (Zervakis and Koutrotsios 2017). There are two main formulas for the production of the substrates employed in mushroom cultivation that have been optimized depending on the species. Both are derived from agricultural by-products such as cereal straw, plant fiber/husk, manure or sawdust: *Correspondence: 1 Department of Plant Sciences, University of Oxford, S Parks Rd, Oxford OX1 3RB, UK Full list of author information is available at the end of the article © The Author(s) 2018. This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. Carrasco et al. AMB Expr (2018) 8:146 1. Composted materials achieved through fermentation and pasteurization (Pardo et al. 2017; Kabel et al. 2017; Vos et al. 2017), designed for the cultivation of Agaricus bisporus (Lange) Imbach (AB) or A. subrufescens Peck (Pardo-Giménez et al. 2014; Pardo et al. 2017), Pleurotus ostreatus (Jacq: Fries) (PO), P. sajor-caju (Fr.) Singer or P. cistidiosus O.K. Mill. (Chang and Miles 2004; Sánchez 2010). 2. Non-composted materials that consist of a mixture of different agricultural by-products as the main ingredients, followed by steam sterilization of the substrate prior to the inoculation of the mycelium. Certain commercial species are produced employing this kind of substrate, including Lentinula edodes (Berk.) Pegler (LE), Auricularia sp., Flammulina velutipes (Curtis) Singer, Pleurotus eryngii (DC.: Fr.) Quel., Agrocybe aegerita (V. Brig.) Singer, Volvariella volvacea (Bull. Ex Fr.) or Hypsizygus marmoreus (Peck) Bigel (Chang and Miles 2004; Estrada et al. 2009; Liang et al. 2016; Xie et al. 2017; Kleofas et al. 2014; Yamanaka 2017). Some cultivated species, like the globally cultivated white button mushroom (A. bisporus), require a casing overlay to cover the colonized substrate in order to induce mushroom fructification (Pardo-Giménez et al. 2017a). Mushroom supplementation is understood as a farming method based on the physical addition of nutritional amendments to compost, during the process of composting, the mixture of raw materials, at spawning or during casing (Estrada et al. 2009; Pardo-Giménez et al. 2012a, 2016). The practice of nutritionally supplementing compost for mushroom cultivation at the time of spawning or casing to maximize crop yield emerged in the 1960s (Schisler and Sinden 1962; Sinden and Schisler 1962; Lemke 1963) and is widely recognized and accepted, however its use can be restricted in some sectors because of technical and economic factors. Important aspects to be considered include, on the one hand, the types of nutrients required and the most suitable time for them to be applied without forgetting, on the other hand, economic costs and profits (Randle 1985). Recently, potential mushroom growth promoting (MGP) fungi and bacteria have been described to stimulate the mycelium growth and promote mushroom fructification, while constituting nitrogen or vitamins reservoirs (Zarenejad et al. 2012; Kertesz and Thai 2018). MGP therefore represent an additional form of supplement that could be supplied separately, or in combination with nutritional supplements, to increase crop yield. Page 2 of 9 The present mini-review compiles the recent advances on the supplementation of substrates employed in mushroom cultivation and aims to shed light on some agronomical aspects regarding this expanding crop (Zhang et al. 2014). Formulation of nutritional additives for mushroom cult (...truncated)