The primary contributor to global warming has been the careless usage of fossil fuels. Urbanization's threat to the depletion of these resources has made it necessary to find alternatives due to the rising demand. Four different forms of biofuels are now available and constitute a possible replacement for fossil fuels. The first generation of biofuels is generated from the edible portion of biomass, the second generation is made from the non-edible portion of biomass, the third generation is made from algal biomass, and the fourth generation is made using molecular biology to improve the algal strain. Second generation biofuels are extremely important because they are derived from non-edible biomass, such as agricultural and agro-industrial wastes rich in cellulose, hemicellulose, pectin, and starch impregnated with lignin, and are hydrolyzed after delignification by physio-chemical or biological pretreatments using ligninases. There has been a lot of research on their production using chemical and enzymatic hydrolysis, but it has not been economically viable in comparison to first generation biofuels due to the formation of several inhibitors with chemical hydrolysis and the high cost of the enzymes. Furthermore, the need for multiple enzymes due to the various types of carbohydrates in the feedstocks makes the enzymatic process too expensive. This article examines the enzymes involved in the hydrolysis of feedstocks for the production of second generation bioethanol, a highly acceptable biofuel.

As β-glucosidases represent the major bottleneck for industrial degradation of plant biomass, great efforts are being devoted both to discover novel and robust versions of these enzymes, as well as to develop efficient and inexpensive ways to produce them. In this work, raw glycerol from chemical production of biodiesel was tested as carbon source for the fungus Talaromyces amestolkiae with the aim of producing enzyme cocktails rich in this activity. Approximately 11 U/mL β-glucosidase were detected in these cultures, constituting the major cellulolytic activity. Proteomic analysis revealed BGL-3 as the most abundant protein and the main β-glucosidase. This enzyme crude was successfully used to supplement a basal commercial cellulolytic cocktail (Cellu-clast 1.5L) for saccharification of pretreated wheat straw, corroborating that even hardly exploitable industrial wastes, such as glycerol, can be used as secondary raw materials to produce valuable enzymatic preparations in a framework of circular economy

The administration of Bacilli to dairy cows exerts a beneficial effect on dry matter intake, lactation performances and milk composition. In this work, two isogenic strains, only differing in the se-cretion level of cellulolytic and xylanolytic enzymes, were compared to establish whether B. subtilis cellulase and xylanase enzymes are involved in the positive effect exerted by these bacteria on animal nutrition. Conveniently, bacteria were grown in a newly designed growth medium based on an inexpensive waste. A multi-factorial study was conducted in which eight feed in-gredients were treated in vitro, using ruminal fluid from cannulated cows, with cultures of the two B. subtilis strains. Feed digestibility and gas production, a parameter linked to feed fermentability, were assessed. Fiber degradability was significantly higher in feeds treated with the en-zyme-overexpressing strain (10% and 5% higher than control treatment with B. subtilis-free media and the parent strain, respectively). This effect was accentuated for the most recalcitrant feeds, in which the benefits of cellulolytic and xylanolytic enzymes were maximized. Fermentability also benefited by the treatment with the enzyme-overexpressing strain, although the trend observed in gas production didn’t reach statistical difference between the two strains, and only minor changes in fermentation profiles were detected. Our results revealed that B. subtilis cellulases and xylanases effectively contribute to improving forage quality, supporting the use of Bacilli as fodder sup-plements to increase animal productivity.

In the present study, the polysaccharide-hydrolyzing secretomes of Irpex lacteus BCC104, Pycnoporus coccineus BCC310, and Schizophyllum commune BCC632 were analyzed in submerged fermentation conditions to elucidate the effect of chemically and structurally different carbon sources on the expression of cellulases and xylanase. Among polymeric substrates, crystalline cellulose appeared to be the best carbon source providing the highest endoglucanase, total cellulase, and xylanase activities. Mandarin pomace as a growth substrate for S. commune allowed to achieve comparatively high volumetric activities of all target enzymes while wheat straw induced a significant secretion of cellulase and xylanase activities of I. lacteus and P. coccineus. A synergistic effect on the secretion of cellulases and xylanases by the tested fungi was observed when crystalline cellulose was combined with mandarin pomace. In I. lacteus the cellulase and xylanase production is inducible in the presence of cellulose-rich substrates but is suppressed in the presence of an excess of easily metabolizable carbon source. These enzymes are expressed in a coordinated manner under all conditions studied. It was shown that the substitution of glucose in the inoculum medium with Avicel provides accelerated enzyme production by I. lacteus and higher cellulase and xylanase activities of the fungus. These results add new knowledge to the physiology of basidiomycetes to improve cellulase production.