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A new type of biosorbent was developed for binding anionic precious metals through cross-linking waste biomass Corynebacterium glutamicum with polyethylenimine (PEI). This biomass was evaluated for the removal and recovery of palladium and compared to commercial adsorbents, such as Amberjet 4200 Cl, Lewatit Monoplus TP 214, SPC-100, and SPS-200. The kinetic experiments revealed that the sorption equilibrium was reached with 30 min for the PEI-modified biomass. The maximum uptake of the biosorbent was 176.8 mg/g, which was calculated using the Langmuir model. The Pd(II) maximum uptake exhibited the following order: Amberjet 4200 Cl>Lewatit Monoplus TP 214>PEI-modified biomass>SPC-100>SPS-200. Acidified thiourea in 1.0M HCl was used to desorb Pd(II) from all of the sorbents examined.

In this study, a mediator-less microbial fuel cell (MFC) inoculated with a sulfate-reducing bacterium (SBR), Desulfovibrio desulfuricans, was equipped with bare and surface-treated graphite felt electrodes. Electrochemical treatment of the anode surface facilitated biofilm formation on the electrode, resulting in rapid and enhanced current production. The maximum current density of the treated anode was 233±24.2mA/m(2), which was 41% higher than that of the untreated anode. The electron transfer rate also increased from 2.45±0.04 to 3.0±0.02μmol of electrons/mg of protein·min. Biofilm formation on the treated anode was mainly due to the strong hydrogen or peptide bonds between the amide groups of bacterial materials (including cytochrome c) and carboxyl groups formed on the electrodes. These results provide useful information on direct electron transfer by SRB in a mediator-less MFC through cytochrome c and the effects of the electrochemical treatment of electrodes on MFC performance.

The production of ethanol from feedstock other than agriculture materials has been promoted in recent years. Some microalgae can accumulate a high starch content (about 44% of dry base) via photosynthesis. Algal biomass, Chlamydomonas reinhardtii UTEX 90, was converted into a suitable fermentable feedstock by two commercial hydrolytic enzymes. The results showed that almost all starch was released and converted into glucose without steps for the cell wall disruption. Various conditions in the liquefaction and saccharification processes, such as enzyme concentration, pH, temperature, and residence time, have been investigated to obtain an optimum combination using the orthogonal analysis. As a result, approximately 235 mg of ethanol was produced from 1.0 g of algal biomass by a separate hydrolysis and fermentation (SHF) method. The main advantages of this process include the low cost of chemicals, short residence time, and simple equipment system, all of which promote its large-scale application.

Rhodococcus sp. YHY01 was studied to utilize various lignin derived aromatic compounds. It was able to utilize p-coumaric acid, cresol, and 2,6 dimethoxyphenol and resulted in biomass production i.e. 0.38 g dcw/L, 0.25 g dcw/L and 0.1 g dcw/L, and lipid accumulation i.e. 49%, 40%, 30%, respectively. The half maximal inhibitory concentration (IC50) value for p-coumaric acid (13.4 mM), cresol (7.9 mM), and 2,6 dimethoxyphenol (3.4 mM) was analyzed. Dimethyl sulfoxide (DMSO) solubilized barley straw lignin fraction was used as a carbon source for Rhodococcus sp. YHY01 and resulted in 0.130 g dcw/L with 39% w/w lipid accumulation. Major fatty acids were palmitic acid (C16:0) 51.87%, palmitoleic acid (C16:l) 14.90%, and oleic acid (C18:1) 13.76%, respectively. Properties of biodiesel produced from barley straw lignin were as iodine value (IV) 27.25, cetane number (CN) 65.57, cold filter plugging point (CFPP) 14.36, viscosity (υ) 3.81, and density (ρ) 0.86.

This study employed a simultaneous gas feeding and cell-recycled reaction (SGCR) system to ferment CO using Eubacterium limosum KIST612. A bubble column reactor was equipped with an ex-situ hollow fiber membrane module to enable cell recycling. The internal gas circulation rate was adjusted by controlling the pump speed to provide sufficient gas supplement to the microorganism. Gas feedings were conducted by either the use of a gas-tight bag (Batch), a pressurized gas cylinder (Continuous), or a sequential combination of the two (Mixed feeding). Mixed feeding mode achieved higher biomass (9.7 g/L) and acetate (9.8 g/L) concentrations than Batch mode (3.2 g/L biomass and 7.0 g/L acetate) or Continuous mode (5.0 g/L biomass and 8.1 g/L acetate). The high acetate titer in Mixed feeding mode was achieved due to the high concentration of cells secured in a short time at the initial operation stage and maintaining a high specific growth rate.

The main downside of utilizing algal biomass for biofuel production is the rigid cell wall which confines the availability of soluble organics to hydrolytic microbes during biofuel conversion. This constraint reduces the biofuel production efficiency of algal biomass. On the other hand, presenting various pretreatment methods before biofuel production affords cell wall disintegration and enhancement in biofuel generation. The potential of pretreatment methods chiefly relies on the extent of biomass liquefaction, energy, and cost demand. In this review, different pretreatments employed to disintegrate algal biomass were conferred in depth with detailed information on their efficiency in enhancing liquefaction and biofuel yield for pilot-scale implementation. Based on this review, it has been concluded that combinative and phase-separated pretreatments provide virtual input in enhancing the biofuel generation based on liquefaction potential, energy, and cost. Future studies should focus on decrement in cost and energy requirement of pretreatment in depth.

In recent years, lignocellulosic biomass has emerged as one of the most versatile energy sources among the research community for the production of biofuels and value-added chemicals. However, biomass pretreatment plays an important role in reducing the recalcitrant properties of lignocellulose, leading to superior quality of target products in bioenergy production. Among existing pretreatment techniques, liquid hot water (LHW) pretreatment has several outstanding advantages compared to others including minimum formation of monomeric sugars, significant removal of hemicellulose, and positive environmental impacts; however, several constraints of LHW pretreatment should be clarified. This contribution aims to provide a comprehensive analysis of reaction mechanism, reactor characteristics, influencing factors, techno-economic aspects, challenges, and prospects for LHW-based biomass pretreatment. Generally, LHW pretreatment could be widely employed in bioenergy processing from biomass, but circular economy-based advanced pretreatment techniques should be further studied in the future to achieve maximum efficiency, and minimum cost and drawbacks.

Lipid production in microalgae can be induced by various stress factors. However, stress induced lipid accumulation requires considerable time leading to the decrease in lipid productivity. Here, we attempted to increase the lipid productivity while maintaining the high growth of Ettlia sp. by optimizing nitrogen concentration and UV exposure in a continuous culture. The biomass and lipid productivities of Ettlia sp. cultured with 150 mg N L-1 and UV-A added PAR were 1.67 ± 0.08 g L-1 d-1 and 0.55 ± 0.05 g L-1 d-1, respectively. Lipid productivity and lipid content were around 43.7% and 33.7% higher, respectively in UV-A treatment compared to the control. Moreover, gene-expression patterns related to antioxidant defense and intracellular ROS levels indicated that UV-A affected certain ROS and antioxidants pathways and successfully induced the lipid accumulation in Ettlia sp. This strategy to activate lipid accumulation can be applied in other microalgae without affecting their growth.

Bermudagrass, reed and rapeseed were pretreated with phosphoric acid-acetone and used for ethanol production by means of simultaneous saccharification and fermentation (SSF) with a batch and fed-batch mode. When the batch SSF experiments were conducted in a 3% low effective cellulose, about 16 g/L of ethanol were obtained after 96 h of fermentation. When batch SSF experiments were conducted with a higher cellulose content (10% effective cellulose for reed and bermudagrass and 5% for rapeseed), higher ethanol concentrations and yields (of more than 93%) were obtained. The fed-batch SSF strategy was adopted to increase the ethanol concentration further. When a higher water-insoluble solid (up to 36%) was applied, the ethanol concentration reached 56 g/L of an inhibitory concentration of the yeast strain used in this study at 38 degrees C. The results show that the pretreated materials can be used as good feedstocks for bioethanol production, and that the phosphoric acid-acetone pretreatment can effectively yield a higher ethanol concentration.