NEW LOW-INPUT MICROBIAL PROCESSES FOR THE ENHANCEMENT OF BREWERS’ SPENT GRAIN

Sustainable production is the creation of goods and services using processes compatible with the protection of the environment and the natural resources to be passed on to future generations. In this context, and also supported strongly by EU policies, the production of craft beer must combine the concept of quality with that of sustainability, favoring a short supply chain and zero waste. This new production culture must translate into an increased and equitable distribution of income along the supply chain. To achieve these goals, it is necessary to understand which phases of the production process can be optimized and which innovations can be adopted in terms of sustainability, to obtain economic advantages. It is therefore strategic to seek product quality starting from local materials, to strengthen the link between beer and the production area, and to increase the sustainability through the valorization of the by-products. The disposal of waste from agro-industrial processes represents a problem with economic and environmental implications. However, waste can be seen as a resource rather than a problem. EU regulations (Directive 2018/851 / EU; Directive 2008/98 / EC) encourage the extraction of valuable components from by-products of the food industry, to produce functional foods, adjuvants, and pharmaceutical preparations, and/or the transformation of waste into soil improvers and fertilizers for agricultural use. In the brewing sector, the management of by-products, which account for approximately 90% of the raw materials used, is one of the critical issues. Brewers’ spent grain (BSG) is the most abundant by-product, after water, and it is obtained from the mashing, with an average yield of about 20 kg per hectoliter of beer. The recovery and valorization of BSG would bring considerable savings to the production costs. Currently, many breweries have agreements with local farmers to give their BSG free of charge as a low-cost supplement for animal feed. Recently, a technological transfer project entitled, “Sustainable Development of Craft Beer in Sardinia” has been financed by the Sardinian Regional Government within the framework of the POR FESR 2014/2020 - PRIORITY AXIS I "SCIENTIFIC RESEARCH, TECHNOLOGICAL DEVELOPMENT AND INNOVATION". This project is being carried out by the researchers of the University of Sassari in collaboration with Porto Conte Ricerche, SOTACARBO, and 22 craft breweries and 12 agricultural companies, with the general objective of making regional brewing production more competitive on the national and international market by favoring the development of innovative and beneficial models of a circular economy. In particular, it is aimed at the identification of microbial processes for the valorization of brewery waste, such as wastewaters and BSG. In this context, the aim of this Ph.D project was to identify and optimize environmentally friendly microbial processes for the valorization of BSG for its reuse as an agricultural soil conditioner and a fertilizer. Providing innovative solutions in the enhancement of BSG will serve to increase the profitability and environmental sustainability of craft microbreweries. The objectives of this research were therefore: • to present the current literature on BSG from a microbiological point of view; • to compare the physiochemical and microbiological quality and safety of vermicompost obtained from both BSG and cow manure using the earthworm E. fetida; • to evaluate from a microbiological and chemical perspective a low-input pre-treatment process designed to make raw BSG palatable for these earthworms; • to evaluate of the possible use of raw BSG as a growth substrate for a microbial-based biofertilizer.

The disposal of waste from agro-industrial processes represents a problem with economic and environmental implications. However, waste can be seen as a resource rather than a problem. EU regulations (Directive 2018/851 / EU; Directive 2008/98 / EC) encourage the extraction of valuable components from by-products of the food industry, to produce functional foods, adjuvants, and pharmaceutical preparations, and/or the transformation of waste into soil improvers and fertilizers for agricultural use. In the brewing sector, the management of by-products, which account for approximately 90% of the raw materials used, is one of the critical issues. Brewers’ spent grain (BSG) is the most abundant by-product, after water, and it is obtained from the mashing, with an average yield of about 20 kg per hectoliter of beer. The recovery and valorization of BSG would bring considerable savings to the production costs. Currently, many breweries have agreements with local farmers to give their BSG free of charge as a low-cost supplement for animal feed. The aim of this Ph.D project was to identify and optimize environmentally friendly microbial processes for the valorization of BSG for its reuse as an agricultural soil conditioner and a fertilizer. Providing innovative solutions in the enhancement of BSG will serve to increase the profitability and environmental sustainability of craft microbreweries. The objectives of this research were therefore: • to present the current literature on BSG from a microbiological point of view; • to compare the physiochemical and microbiological quality and safety of vermicompost obtained from both BSG and cow manure using the earthworm E. fetida; • to evaluate from a microbiological and chemical perspective a low-input pre-treatment process designed to make raw BSG palatable for these earthworms; • to evaluate of the possible use of raw BSG as a growth substrate for a microbial-based biofertilizer.