Because of increasing concerns of the exhausting resource and ecological and environmental problems in the petro-based industry, utilization of renewable resources is considered as one of the solutions for sustainable development. Biomass is one of the most abundant and most important renewable resources, which can be used as feedstocks to produce energy, platform chemicals and materials in biorefinery . Biorefinery is a promising concept as an alternative to petro-based refinery industry.
Succinic acid, a four-carbon dicarboxylic acid produced as an intermediate of the tricarboxylic acid cycle or as an end product of anaerobic metabolism, has been widely used in the agricultural, food and pharmaceutical industries . Currently, succinic acid is considered as one of the key platform chemicals used directly in preparation of biodegradable polymers such as polybutylene succinate and polyamides and as a raw material to synthesize compounds in the C4 family, including 1,4-butanediol, tetrahydrofuran, N-methyl pyrolidinone, 2-pyrrolidinone and γ-butyrolactone [3, 4]. Due to its independence from petroleum as a raw material, environmental benefit and CO2 sequestration, biological production of succinic acid from renewable resources has attracted significant interest over the recent years [5, 6]. A wide variety of strains have been applied for the production of succinic acid, such as Actinobacillus succinogenes , Mannheimia succiniciproducens , Anaerobiospirillum succiniciproducens , and recombinant Escherichia coli. Due to the well-understood physiology and the well-established engineering tools, E. coli has been studied intensively and has showed great advantages in succinic acid production such as a wide range of carbon sources and tolerance to the complicated environment . So far, bio-succinic acid cannot compete with that derived from petro-based processes due to the high cost of the raw materials. In this situation, the biorefinery strategy opens a promising way for the production of succinic acid since cheaper biomass waste potentially can be utilized [12, 13].
Biorefinery consist of two platforms: a sugar platform and a thermal platform. Nowadays, renewable biomass has been intensively investigated to produce bio-fuels and chemicals via the sugar platform . This process usually includes pretreatment of biomass, obtaining sugars and the final products fermentation. Meanwhile, substantial research is being carried out to produce alternative fuels from biomass to replace the gasoline and diesel via thermal platform . Fast pyrolysis is one of the promising thermal processes, which is conducted at a median temperature (400 – 600°C) in the absence of oxygen at a high heating rate [16, 17]. Production of bio-oil by pyrolysis of biomass attracts large attention since it has a higher energy density and has potentials for partial replacement of diesel and gasoline fuels . However, the bio-oil cannot be used directly as transportation fuel due to its high oxygen content (40–50 w/w%), the low H/C ratios and the high water content (15–30 w/w%). Upgrading technologies such as deep deoxygenation is essential to promote the usage of bio-oil . Bio-oil can be separated into two fractions after adding water, a heavy organic fraction and an aqueous fraction (AP-bio-oil). The heating value of pyrolytic lignin which is derived from the organic fraction is higher than the crude bio-oil because of its lower oxygen content [20, 21]. Thus, it seems to be a good way to separate bio-oil into an aqueous phase and an organic phase before upgrading it . It is reported that the AP-bio-oil contains many different components with the “sugar constituents” being a major part [23, 24]. However, the concentrations of the components are low and are difficult to upgrade to a useful fuel. The possibility of AP-bio-oil usage was therefore investigated, that is, by applying a biotechnological process. It is of significant value to transform AP- bio-oil into value added chemicals. From authors’ knowledge, production of succinic acid from bio-oil via biological processes is not found in the open literature.
In this study, bio-oil was separated into an organic phase which can be easily upgraded to transportation fuel and an aqueous phase with water soluble organic components. The influence of AP- bio-oil on the bacterial growth and fermentation was investigated. Meanwhile glucose from enzymatic hydrolyzed corn stover was used to facilitate better fermentation process. This study thereby integrates the two biorefinery platforms with focus on production of succinic acid from bio-oil, which provides new insight into production of succinic acid from AP-bio-oil and corn stover.