H. Zabed

Bioethanol production from fermentable sugar juice.

Bioethanol production from renewable sources to be used in transportation is now an increasing demand worldwide due to continuous depletion of fossil fuels, economic and political crises, and growing concern on environmental safety. Mainly, three types of raw materials, that is, sugar juice, starchy crops, and lignocellulosic materials, are being used for this purpose. This paper will investigate ethanol production from free sugar containing juices obtained from some energy crops such as sugarcane, sugar beet, and sweet sorghum that are the most attractive choice because of their cost-effectiveness and feasibility to use. Three types of fermentation process (batch, fed-batch, and continuous) are employed in ethanol production from these sugar juices. The most common microorganism used in fermentation from its history is the yeast, especially, Saccharomyces cerevisiae, though the bacterial species Zymomonas mobilis is also potentially used nowadays for this purpose. A number of factors related to the fermentation greatly influences the process and their optimization is the key point for efficient ethanol production from these feedstocks.

Water quality assessment of an unusual ritual well in Bangladesh and impact of mass bathing on this quality

A sacred ritual well with continuously discharging of methane gas through its water body was studied for physicochemical and microbiological quality in three seasons and during ritual mass bathing. Most of the physicochemical parameters showed significant seasonal variations (P<0.05) and a sharp fluctuation during mass bathing. Dissolved oxygen (DO) was found negatively correlated with temperature (r=-0.384, P<0.05), biochemical oxygen demand (BOD) (r=-0.58, P<0.001) and ammonia (r=-0.738, P<0.001), while BOD showed positive correlation with chemical oxygen demand (COD) (r=0.762, P<0.001) and ammonia (r=0.83, P<0.001). Simple regression analysis also yielded significant linear relationship in DO vs. temperature (r(2)=0.147, P<0.05), DO vs. ammonia (r(2)=0.544, P<0.001) and BOD vs. DO (r(2)=0.336, P<0.001). A total of eight microbial indicators were studied and found that all of them increased unusually during mass bathing comparing with their respective seasonal values. Total coliforms (TC) were found positively correlated with fecal coliforms (FC) (r=0.971), FC with Escherichia coli (EC) (r=0.952), EC with intestinal enterococci (IE) (r=0.921), fecal streptococci (FS) with IE (r=0.953) and Staphylococcus aureus (SA) with Pseudomonas aeruginosa (PA) (r=0.946), which were significant at P<0.001. Some regression models showed significant linear relationship at P<0.001 with r(2) value of 0.943 for FC vs. TC, 0.907 for EC vs. FC, 0.869 for FS vs. FC, 0.848 for IE vs. EC and 0.909 for IE vs. FS. The overall results found in this study revealed that well water is suitable for bathing purpose but the religious activity considerably worsen its quality.

An Overview on the Application of Ligninolytic Microorganisms and Enzymes for Pretreatment of Lignocellulosic Biomass

Generation of biofuels from lignocellulosic biomass has received much interest in recent times to achieve an alternative energy source over conventional fossil fuels. Pretreatment is a vital step in the bioconversion of lignocellulosic biomass into biofuels, which is required to break down the lignocellulosic network of biomass. It is necessarily applied prior to the production of bioalcohols (bioethanol and biobutanol), biohydrogen, and biogas through fermentation. Delignification is the main objective of pretreatment that releases polysaccharides from the lignocellulosic matrix and increases enzymatic digestibility of cellulose. Although pretreatment can be done by using different physical, chemical, physicochemical, and biological methods, the latter is considered more promising as it is less expensive and eco-friendly, generates low or no inhibitors, and consumes relatively lower energy (steam and electricity). Many naturally occurring ligninolytic microorganisms and enzymes are used for delignification of biomass biologically. The aim of this chapter is to present an overview of different ligninolytic microorganisms (fungi and bacteria) and their enzymes for biological pretreatment of lignocellulosic biomass.