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Biodegradation of phenolic compounds in wastewater can be effectively carried out in packed bed reactors (PBRs) employing immobilized microorganisms. A low-cost, reusable immobilization matrix in PBR can provide economic advantages in large scale removal of high concentration phenol. In this study, we evaluated the efficiency and reusability of sugarcane bagasse (SCB) as a low-cost immobilization support for high strength phenol removal in recirculating upflow PBR. An isolated yeast Candida tropicalis PHB5 was immobilized onto the SCB support and packed into the reactor to assess phenol biodegradation at various influent flow rates. Scanning electron microscopy exhibited substantial cell attachment within the pith and onto the fibrous strand surface of the SCB support. The PBR showed 97% removal efficiency at the initial phenol concentration of 2400 mg L−1 and 4 mL min−1 flow rate within 54 h. Biodegradation kinetic studies revealed that the phenol biodegradation rate and biodegradation rate constant were dependent on the influent flow rate. A relatively higher rate of biodegradation (64.20 mg g−1 h−1) was found at a flow rate of 8 mL min−1, indicating rapid phenol removal in the PBR. Up to six successive batches (phenol removal >94%) were successfully applied in the PBR using an initial phenol concentration of 400–2400 mg L−1 at a flow rate of 4 mL min−1 indicating the reusability of the PBR system. The SCB-immobilized C. tropicalis could be employed as a cost-effective packing material for removal of high strength phenolic compounds in real scale PBR. Image 1 • Sugarcane bagasse was used as an immobilization support and packing material for PBR. • The PBR with immobilized C. tropicalis showed 97% phenol removal at 2400 mg L−1. • A maximum phenol biodegradation rate of 64 mg g−1 h−1 was achieved. • Repeated use of the packed bed reactor was possible for up to six batches. [ABSTRACT FROM AUTHOR]

Lignin is the principal impediment in the production of biofuel from different lignocellulosic sources through hydrolysis, saccharification and fermentation route. The two main types of treatment for lignin separation from the other main constituent plant materials, hemicellulose and cellulose, are biodegradation and the chemical degradation including base-catalyzed, acid-catalyzed, ionic liquids-assisted lignin depolymerization. Severe reaction conditions, such as high pressure, high temperature and extreme pH, are being in practice for chemical degradation and result in the requirement of specially designed reactors. This leads to high costs of facility and handling along with the inadvertent generation of toxins. Biological degradation seems to be widespread and cost effective if enzymes degrading lignin could be produced by isolation of fungi. Bacterial strains could also be prepared that produce the lignin-splitting enzyme laccase. The present article reviews the available processes for lignin degradation during lignocellulosic conversion of ethanol and discusses the research gaps in these fields. [ABSTRACT FROM AUTHOR]

Though gasification of biomass in fluidized bed system is an efficient way of biomass utilization, limited experimental data on the fluidized bed biomass gasification are available in open literature. Therefore, an experimental study of biomass gasification is conducted using a laboratory scale bubbling fluidized bed gasifier. Rice husk is used as the biomass material and air-steam mixture is used as the gasifying agent. As the non-granular nature of rice husk makes it difficult to fluidize, silica sand is used as the inert bed material to help in fluidization. Parametric studies are performed to determine the effects of reactor temperature, equivalence ratio, and steam-to-biomass ratio on the product gas composition and the heating value. The results show that both hydrogen percentage and the heating value of the product gas increase with increase in gasification temperature and steam-to-biomass ratio, but they decrease with increase in equivalence ratio. The maximum heating value (4.26 MJ/Nm3) and hydrogen percentage (13.1%) are obtained at the gasification temperature of 850 °C, equivalence ratio of 0.35 and the steam-to-biomass ratio of 0.8. [ABSTRACT FROM AUTHOR]

A proper waste management practice such as anaerobic digestion for the waste generated by the agro-food industries could minimize the amount of material disposal to landfill. In our study, the improvement of methane production was elucidated through the pretreatment optimization of the mixed fruit wastes (FW). Dilute acetic acid pretreatment of FW was optimized in order to increase the bioavailability and microbial accessibility. A maximum sugar recovery of 95% was achieved from the pretreated FW under the optimized conditions (0.2 M acetic acid, 62.5 °C, and 30 min). Fourier transform infrared spectroscopy (FTIR) and Thermogravimetric (TG) analyses verified the presence of cellulosic material in the pretreated FW. X-ray diffraction (XRD) analysis indicated that the crystallinity index was increased to 56% after the disruption of complex hemicellulosic structures during pretreatment. Increased porosity and surface roughness of pretreated FW for better microbial attachment were confirmed in scanning electron microscopy (SEM). Anaerobic digestion showed increased methanogenic activity (10.17 mL g −1 VS initial d −1 ) in pretreated FW, during 86-day experimental period due to better microbial attachment and accessibility during the digestion process. Higher methane yield of 53.58 mL g −1 VS initial was observed in pretreated FW. Thus, acetic acid pretreatment is an effective method to improve the utilization and conversion of FW to methane. [ABSTRACT FROM AUTHOR]