Intensifying ethanol production from brewer’s spent grain waste: Use of whole slurry at high solid loadings

Abstract

This work targets the valorization of brewer's spent grain (BSG) waste by ethanol production, providing strategies for increasing titers in the multiple process steps involved. High solid loadings and use of whole slurry from the pretreatment were evaluated, aiming to achieve high ethanol concentration and yield. As variability in BSG chemical composition presents a challenge for their valorization, six different BSGs were chemically characterized, which allowed the selection of two with high polysaccharide content. High solid loadings (up to 25%) were employed for the pretreatment of selected BSGs by autohydrolysis, an environmentally friendly process, to improve enzymatic saccharification and extract fermentable sugars as oligosaccharides and monosaccharides. As a result, high glucose concentrations (43.7 and 57.7 g L −1) and glucose yield (85.9 and 70.6%) were obtained from the saccharification of the pretreated BSG whole slurry at 20 and 25% solid loading, respectively. Whole slurries from autohydrolysis were used as substrate for ethanol production by hybrid saccharification and fermentation. Two different Saccharomyces cerevisiae strains were evaluated and high ethanol concentration (42.27 g L −1) at a high yield (94.0%) was achieved. The results attained by the combined intensification approaches qualify BSG waste as a valuable renewable resource for cost-effective ethanol production.

Development of a sustainable bioprocess based on green technologies for xylitol production from corn cob

“…The effectiveness of pretreatments at high solid loadings (> 15 %) has been demonstrated in several strategies, such as the process developed by Inbicon AS (Denmark) using hydrated wheat straw with recycled condensate or the wet explosion pretreatment of lobelly pine (Xiros et al, 2014). Similar solid loadings (20 and 25 %) were also tested for hydrothermal treatment of brewer´s spent grain, generating higher oligosaccharides concentration using 25 % of solid loading in the pretreatment (Pinheiro et al, 2019). In addition, presoaked wheat straw was maintained at temperatures between 195-205°C and residence time in the range of 6-12 min by injection of stream, resulting in a concentration of solids in the reactor between 23% and 28% (w/w), with the correspondent whole slurries being used for ethanol production by SSF (Jørgensen et al, 2007).…”

The role of microorganisms on biotransformation of brewers’ spent grain

“…Ethanologenic microorganisms have been used to produce ethanol from these hydrolyzed BSG, including Saccharomyces cerevisiae and Zigosaccharomyces rouxii (Liguori et al 2015 ). In particular, the high gravity brewing yeast S. cerevisiae BLGII 1762 and S. cerevisiae PE-2 isolated from the Brazilian bioethanol industry produce ethanol with yields of between 23 and 81% (Pinheiro et al 2019 ). In addition, hemicellulosic hydrolysates of BSG have been used to produce microbial biomass and xylitol using Debaryomyces hansenii CCMI 941 (Carvalheiro et al 2007 ) and Candida guilliermondii FTI 20037 (Mussatto and Roberto 2005 ).…”

Caracterização Química Do Bagaço De Malte E Avaliação Do Seu Potencial Para Obtenção De Produtos De Valor Agregado

“…Este método quantifica o teor de nitrogênio total na amostra, sendo este convertido em teor de proteínas utilizando fator de conversão adequado. Para o bagaço de malte, o fator utilizado foi 6,25, assim como nos estudos realizados por Pinheiro et al (2019), Wilkinson et al (2014) e Mussatto e Roberto (2006).…”

“…Ainda assim foram obtidos rendimentos próximos a 70% do etanol teórico. Pinheiro et al (2019) focaram seu estudo na razão massa/volume do carregamento de sólidos, utilizando prétratamento hidrotérmico sem catalisador (água, 170 ºC, 5 minutos) e sacarificação enzimática. O melhor cenário apresentado foi para carga de 25% sólidos, fornecendo um rendimento de 94% em etanol.…”

“…Entre as hemiceluloses, os polímeros constituintes mais encontrados no bagaço de malte são xilana e arabinana, formados pelos açúcares xilose e arabinose, respectivamente (MUSSATTO; PINHEIRO et al, 2019;QIN et al, 2018). Já entre as proteínas, destacam-se as hordeínas, compondo até 60% das proteínas do grão (LINSKENS; JACKSON, 1988;MOLINA-CANO et al, 2001).…”