Bioethanol Production from Brewers Spent Grains Using a Fungal Consolidated Bioprocessing (CBP) Approach

Abstract

Production of bioethanol from brewers spent grains (BSG) using consolidated bioprocessing (CBP) is reported. Each CBP system consists of a primary filamentous fungal species, which secretes the enzymes required to deconstruct biomass, paired with a secondary yeast species to ferment liberated sugars to ethanol. Interestingly, although several pairings of fungi were investigated, the sake fermentation system (A. oryzae and S. cerevisiae NCYC479) was found to yield the highest concentrations of ethanol (37 g/L of ethanol within 10 days). On this basis, 1 t of BSG (dry weight) would yield 94 kg of ethanol using 36 hL of water in the process. QRT-PCR analysis of selected carbohydrate degrading (CAZy) genes expressed by A. oryzae in the BSG sake system showed that hemicellulose was deconstructed first, followed by cellulose. One drawback of the CBP approach is lower ethanol productivity rates; however, it requires low energy and water inputs, and hence is worthy of further investigation and optimisation.

Evolution toward the utilization of mango leaves as lignocellulosic material in bioethanol production: A review of process parameter and integrated technologies

“…CBP is a process that combines synthesis of cellulase, enzymatic saccharification, and fermentation of monosugars into bioethanol in a single vessel. CBP is also recognised as direct microbial conversion . The most notable advantage of CBP is that this process entails a lower production cost in comparison to other fermentation technology because of the “in situ” saccharification enzyme production in the vessel .…”

“…A fermentation process which was cocultured with C. thermocellum and Thermoanaerobacterium saccharolytium produced 0.41 g/g avicel of bioethanol . Although genetic modification have improved the ability of the microorganisms to perform in CBP, this process is still indoubt due to various difficulties faced during the gene transfer phase . The complications include improper folding of several secretory proteins and adverse effects on cell performance due to co‐expression of multiple heterologous genes .…”

“…CBP is also recognised as direct microbial conversion. 11,90 The most notable advantage of CBP is that this process entails a lower production cost in comparison to other fermentation technology because of the "in situ" saccharification enzyme production in the vessel. 66 CBP depends majorly on a single microorganism or coculture for the convertion process of LCM to bioethanol.…”

“…92 Although genetic modification have improved the ability of the microorganisms to perform in CBP, this process is still indoubt due to various difficulties faced during the gene transfer phase. 90,93 The complications include improper folding of several secretory proteins and adverse effects on cell performance due to co-expression of multiple heterologous genes. 94 Thus, it is very much essential to overcome those challenges for the development of an efficient CBP.…”

Procesamiento de la Cascarilla de Cebada Cervecera por Vía Enzimática para la Obtención de Azúcares Fermentables

“…Por otro lado, las conversiones por ruta biológica son preferidas a la química por ser más selectivas y promisorias para la consecución de etapas más limpias, aunque debido la complejidad de la biomasa lignocelulósica exige múltiples procesos para lograr eficiencia en las operaciones; adicionalmente, la lentitud de las reacciones biotecnológicas es una limitación y se requieren optimizar los tiempos de hidrólisis, rendimientos y productividad (Alvira et al, 2010). En este contexto, el uso de aplicaciones enzimáticas para la degradación de materia orgánica ha sido ampliamente investigado en la producción de biocombustibles; debido a la naturaleza de los residuos orgánicos de fuente agro-industrial se han reportado evaluaciones de diferentes enzimas hidrolíticas con actividad β-glucanasa, celulasa, hemicelulasa, xilanasa, proteasas, lipasas (Wilkinson et al, 2017;Ravindran y Jaiswal, 2016) y enzimas con actividad ligninolítica como peroxidasas y lacasas (El-Naggar et al, 2014). La accesibilidad a la matriz polimérica se convierte en un desafío, entre las propiedades estructurales que dificultan el proceso de hidrólisis enzimática se menciona el grado de polimerización, hidrofobicidad, cristalinidad, área superficial, entre otras.…”