Review article Microbial-processing of fruit and vegetable wastes for production of vital enzymes and organic acids: Biotechnology and scopes Sandeep K. Panda a,n , Swati S. Mishra b , Eugenie Kayitesi a , Ramesh C. Ray c a Department of Biotechnology and Food Technology, Faculty of Science, University of Johannesburg, P. O. Box 17011, Doornfontein Campus, Johannesburg, South Africa b Department of Biodiversity and Conservation of Natural Resources, Central University of Orissa, Koraput 764020, India c ICAR-Regional Center of Central Tuber Crops Research Institute, Bhubaneswar 751019, India article info Article history: Received 28 September 2015 Received in revised form 31 December 2015 Accepted 31 December 2015 Keywords: Fruit and vegetable wastes Improvement of microbial strains Microbial processing Enzymes Organic acids Solid state fermentation Submerged fermentation abstract Wastes generated from fruits and vegetables are organic in nature and contribute a major share in soil and water pollution. Also, green house gas emission caused by fruit and vegetable wastes (FVWs) is a matter of serious environmental concern. This review addresses the developments over the last one decade on microbial processing technologies for production of enzymes and organic acids from FVWs. The advances in genetic engineering for improvement of microbial strains in order to enhance the production of the value added bio-products as well as the concept of zero-waste economy have been briefly discussed. & 2015 Elsevier Inc. All rights reserved. 1. Introduction With the rise in population on the planet, researchers are working towards increasing the yield of food materials, especially fruits, vegetables and cereals to meet the demand. The global production of fruits and vegetables is in the increasing trend and having been recorded as 1.74 billion tons in 2013; 9.4% more than in 2012, when it amounted to 1.59 billion tons (World Farmers Organization, 2014). For example, India is the second largest pro- ducer of fruits and vegetables with a global production share of 10% and 14%, respectively (Das and Mondal, 2013; Ingale et al., 2014). The fruit production of India rose from 0.04 billion tons in 2001–2002 to 0.08 billion tons in 2012–2013. Similarly, the ve- getable production has increased from 0.08 billion tons in 2001– 2002 to 0.16 billion tons in 2012–2013 (Indian Horticultural Da- tabase, 2013). Out of the total fruit and vegetable production in India, 30–40% of the total weight (about 50 million tons) is dis- carded as waste due to various reasons which has a worth of US $483.9 million (Sridevi and Ramanujam, 2012). Likewise, South Africa produces 8.2 million tons of fruits and vegetables per annum (FAO FAOSTAT, 2010a, 2010b). In South Africa it has been estimated that fruit and vegetable wastes (FVWs) contribute 47% of the total food waste generated which is around 4.2 million tons per annum (Oelofse and Nahman, 2013). In the United States, 40% of the food (including fruits and vegetables) which is equal to $165 billion/annum, are wasted uneaten (Gunders, 2012). Although food wastes are used as one of the major components for land filling in the US, it is not cost effective as the waste's main constituent is moisture (Gunders, 2012). FVWs are generated in different stages of supply chain, from farm to fork. In US, 7% of the planted crops including fruits and vegetables are not harvested every year (Kantor et al., 1997). As per the collective data obtained for USA, Canada, Australia and New Zealand, the total loss of fruits and vegetables is 52% of the total production. The major loss (20%) has been reported during production and harvesting (FAO, 2011). Significant amount of FVWs are also generated from processing units such as pickle, sauces, puree and juice. FVWs generated from industrial processing account for 30–50% of the input materials (Di Donato et al., 2011). Pollution of soil and water caused by the disposal of bulk amount of FVWs is a matter of serious concern. Additionally, the food wastes emit significant amount of green house gas that has been estimated to be 4.14 t of CO 2 equivalent per ton of food wasted (Oelofse and Nahman, 2013). However, FVWs are rich in moisture, carbohydrates and other compounds depending upon Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/envres Environmental Research http://dx.doi.org/10.1016/j.envres.2015.12.035 0013-9351/& 2015 Elsevier Inc. All rights reserved. n Corresponding author. E-mail addresses: sandeeppanda2212@gmail.com, sandeepp@uj.ac.za (S.K. Panda). Environmental Research 146 (2016) 161–172