Increasing alcohol yield by selected yeast fermentation of sweet sorghum. II. Isolation and evaluation of mutants and wild types for ethanol production

Utilization of biomass for production of second generation bioethanol was considered as a way to reduce burdens of fossil fuel in Pakistan. The materials wheat straw, rice straw, cotton stalk, corn stover, and peel wastes were used in this experiment. Various parameters, such as acidic and alkali pretreatment, enzymatic hydrolysis by cellulases, and effect of proteases inhibitors on ethanol production, were examined. Fermentation was completed by the yeasts Saccharomyces cerevisiae and Clostridium thermocellum separately, and their ethanol production were compared and maximum ethanol yield was obtained with wheat straw i.e.,11.3 g/L by S. cerevisiae and 8.5 g/L by C. thermocellum. Results indicated that a higher quantity of sugar was obtained from wheat straw (19.6 ± 1.6 g/L) followed by rice straw (17.6 ± 0.6 g/L) and corn stover (16.1 ± 0.9 g/L) compared to the other evaluated biomass samples. A higher yield of ethanol (11.3 g/L) was observed when a glucose concentration of 21.7 g/L was used, for which yeast fermentation efficiency was 92%. Results also revealed the increased in ethanol production (93%) by using celluases in combination with recombinant Serine protease inhibitors from C. thermocellum. It is expected that the use of recombinant serpins with cellulases will play a major role in the biofuel production by using agricultural biomass. This will also help in the economics of the biofuel.

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Bioethanol Production From Leaves of Quercus Infectoria in Kurdistan Region

10.21203/rs.3.rs-93292/v1 ◽

2020 ◽

Author(s):

Bawar Tahir ◽

Xiaoqing Wang ◽

Yuan Zhong ◽

Hassan Mezori ◽

Yan Liu ◽

...

Keyword(s):

Enzymatic Hydrolysis ◽

Ethanol Production ◽

Positive Energy ◽

Yeast Fermentation ◽

Kurdistan Region ◽

Acid Pretreatment ◽

Positive Energy Balance ◽

Ethanol Production Rate ◽

Hydrolysis Conditions ◽

Quercus Infectoria

Abstract Quercus infectoria is one of the most abundant native oak species in the Kurdistan region of Iraq. This study focused on utilizing leaves of Quercus infectoria for ethanol production in the region. A typical three-step conversion process of acid pretreatment, enzymatic hydrolysis, and yeast fermentation was investigated to produce ethanol from the leaves. Under the selected acid pretreatment and enzymatic hydrolysis conditions, the glucose and xylose concentrations in the hydrolysates reached 11.4 g/L and 16.8 g/L, respectively, with the corresponding sugar conversions of 42.8% and 99.8%. A yeast strain, Kluyveromyces marxianus, was used to ferment mono-sugars in the hydrolysates for ethanol production. The ethanol production rate and conversion of K. marxianus in the fermentation were 0.17 g/L/h and 27%. The techno-economic analysis further concluded that a regional ethanol biorefinery can be established in the Zawita sub-district, Iraq to utilize Q. infectoria leaves to produce 200,000,000 kg ethanol/year with a positive energy balance of 745,052,623 MJ/year. The net annual revenue of the biorefinery is $123,692,804. The payback period of the biorefinery is 10 years.

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