Browsing by Author "Willoughby, Nicholas"

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    Enhanced 2,3-Butanediol production by mutant Enterobacter ludwigii using Brewers’ spent grain hydrolysate: process optimization for a pragmatic biorefinery loom
    (Elsevier, 2021-06-18) Amraoui, Yassin; Prabhu, Ashish A.; Narisetty, Vivek; Coulon, Frederic; Chandel, Anuj Kumar; Willoughby, Nicholas; Jacob, Samuel; Koutinas, Apostolis; Kumar, Vinod
    2,3-Butanediol (BDO) is a fossil-based versatile bulk chemical with a multitude of applications. BDO can also be synthesized using microbial cell factories harnessing renewable feedstocks. However, the high cost of the substrate via microbial route impedes commercial manufacturing of BDO. Therefore, identification of cheaper substrates could make bio-based BDO production more cost-competitive. Brewers’ spent grain (BSG), a major by-product of breweries, is an inexpensive source of fermentable sugars and proteins. In the present study, we have attempted the bioproduction of BDO by Enterobacter ludwigii using BSG as feedstock. A random E. ludwigii mutant obtained after treatment with ethyl methane sulfonate (EMS) resulted in a BDO titer (9.5 g/L), ~30% higher in comparison to the wild type strain with a yield of 0.48 gBDO/gGlucose approaching the theoretical yield of 0.50 gBDO/gGlucose. The enzymatic hydrolysis of microwave-assisted alkali pretreated BSG was optimized using the statistical Taguchi design. The BSG hydrolysis under optimal conditions (pH: 6.0; temperature: 50 °C; BSG: 10% w/v; enzyme loading: 2% v/v) resulted in a glucose yield of 0.25 gGlucose/gBiomass. The uncontrolled pH was found to be more beneficial for BDO accumulation from BSG hydrolysate in batch bioreactor cultivation as compared with controlled one. The fed-batch cultivation with forced pH fluctuations at an aeration rate of 2.0 vvm resulted in BDO accumulation of 118.5 g/L from glucose-rich BSG hydrolysate with the yield and productivity of 0.43 g/g and 1.65 g/L.h, respectively. To the best of our knowledge, this is the first study on BDO production from BSG.
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    Recycling bread waste into chemical building blocks using a circular biorefining approach
    (Royal Society of Chemistry, 2021-09-06) Narisetty, Vivek; Cox, Rylan; Willoughby, Nicholas; Aktas, Emel; Tiwari, Brijesh; Matharu, Avtar Singh; Salonitis, Konstantinos; Kumar, Vinod
    Food waste is a global problem, causing significant environmental harm and resulting in substantial economic losses globally. Bread is the commonly wasted food item in the developed world and presents a severe problem for the majority of European nations. It is the second most wasted food item in the UK after potatoes, with an equivalent of 20 million slices of bread thrown away daily. Bread is a starchy material and a rich and clean source of easily extractable fermentable sugars – this is in direct contrast to lignocellulosic feedstocks where harsh physical, chemical and/or enzymatic pretreatment processes are required for release of fermentable sugars. Furthermore, these necessary lignocellulosic pretreatment methods often produce sugars contaminated with fermentation inhibitors. Therefore, bread waste presents a clear opportunity as a potential carbon source for novel commercial processes and, to this end, several alternative routes have been developed to utilize bread waste. Possibilities for direct recycling of bread waste within the food industry are limited due to the relatively short material lifetime, stringent process and hygiene requirements. Anaerobic digestion (AD) and incineration are commonly employed methods for the valorisation of bread waste, generating limited amounts of green energy but with little other environmental or economic benefits. Most food wastes and by-products in the UK including bakery waste are treated through AD processes that fail to harness the full potential of the these wastes. This short communication reviews the challenges of handling bread waste, with a focus on a specific UK scenario. The review will consider how bread waste is generated across the supply chain, current practices to deal with the waste and logistics challenges in waste collection. The presence of clean and high-quality fermentable sugars, proteins and other nutrients in bread make it an ideal substrate for generating chemicals, fuels, bioplastics, pharmaceuticals and other renewable products through microbial fermentations. We suggest potential applications for recycling bread waste into its chemical building blocks through a fermentative route where a circular biorefining approach could maximize resource recovery and environmental savings and eliminate waste to as close to zero as possible.
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    Recycling potential of brewer's spent grains for circular biorefineries
    (Elsevier, 2022-12-23) Agrawal, Deepti; Gopaliya, Deeksha; Willoughby, Nicholas; Khare, Sunil K.; Kumar, Vinod
    Brewer's spent grain (BSG) is the major by-product of the brewing industry. BSG is principally composed of carbohydrates and proteins, with substantial amount of lipids. Presently, BSG usage is restricted to low-grade applications such as ruminant feed or landfills. The high volume, nutrient-rich composition, low cost (€35/ton), abundance, and around the year availability, makes it a promising and renewable feedstock for biorefinery development. The current review begins with beer production process, where BSG is produced. Further, it appraises emerging biotechnological advancements and green processes targeting BSG valorisation ensuring maximal resource recovery. Particularly, it illustrates diverse marketable products obtained by repurposing carbohydrate and protein fraction of BSG using either isolated or cascading approach. We believe that this review will encourage more research groups to work on developing innovative technologies for integrated and holistic valorisation of BSG. Inclusive efforts towards reduced water consumption and waste minimisation is further advocated, which are presently primary challenges associated with beer industry. It will leave a significant imprint on environmental sustainability and pave a way for developing circular bio-based economy.