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.

Biological pretreatment of lignocellulosic residues has the potential to serve as a sustainable, less energy-intensive alternative to harsh chemical treatments for enhancing cellulose accessibility, despite the requirement of a lengthy incubation period. The study characterized the simultaneous delignification of corn stover by the white-rot fungus Pyrenophora phaeocomes S-1, as well as the co-production of a ligno-hemicellulolytic enzyme cocktail consisting of laccase, xylanase, and mannanase. The maximum yields of all three components of the cocktail were achieved after just 4 days of incubation under solid-state conditions. Following a 40-day fermentation period, we achieved a cellulose recovery of 44.25 ± 1.72%, attributed to the activities of 133.88 U/gds of laccase, 14.93 U/gds of xylanase, and 1.34 U/gds of mannanase co-produced by the fungus in the medium. Subsequently, through the extraction of biologically treated biomass with 0.5N NaOH after 40 days, the cellulose recovery increased to 66.4 ± 1.39%. Enzymatic hydrolysis of the same, employing only 5 FPU/gds of in-house produced cellulases, resulted in the liberation of 397.84 mg/gds of total reducing sugars after 144h. The findings of this study encourage further optimization of biological pretreatment of lignocellulosic residues and enzymatic hydrolysis to enhance the yields of total reducing sugars for their valorization.

The aim of this study was to investigate the potential of converting potato peel waste into bio ethanol using an in-house produced multi-enzyme preparation. To achieve this, a variety of pre-treatment strategies, including thermal, chemical, and thermo-chemical methods, were applied to the potato peels. These included boiling for 30 and 60 min, steam at varying pressures and times, and different concentrations of chemicals such as H2SO4, HNO3, CH3COOH, HCl, NaOH, Ca(OH)2, KOH, NH3, and H2O2, either alone or in combination with steam. The pre-treated potato peels were then enzymatically hydrolyzed using a crude multi-enzyme cocktail derived from solid-state fermentation of wheat bran by a natural variety of Aspergillus niger P-19, containing cellulases, hemicellulases, pectinase, and amylases. The most effective pre-treatment combination was found to be 3% H2SO4 followed by steam under pressure and enzymatic hydrolysis using the crude multi-enzyme preparation. This combination resulted in the highest yield of reducing sugars (141.04 ±12.31 g/l) with a 98.49% carbohydrate conversion at a 20% substrate loading, giving an ethanol yield of 43.2 g/l. Furthermore, supplementing the medium with peptone, (NH4)(H2PO4), and ZnSO4 at 0.1%w/v each with 22% and 24% solid, respectively, resulted in appreciable yields of 51.67 and 54.75 g/l, further enhancing the ethanol yield.

The study addresses the management of kitchen waste by transforming it into biofertilizer formulations utilizing an effective in-house developed multi-enzyme preparation. A separate hydrolysis and fermentation bioprocessing approach which in particular relates to the application of a separate enzyme preparation from Aspergillus niger P-19 to separately hydrolyze kitchen waste, followed by the growth of Klebsiella pneumoniae AP-407 in the liquid hydrolysate as well with simultaneous production of carrier-based biofertilizer. In liquid and carrier-based biofertilizers, the viable cell count reaches 3.00 × 1012 CFU/ml and 3.00 × 1012 CFU/g, respectively. The current study adopts a novel process technique for the manufacturing of both carrier and liquid biofertilizers, adopting a zero-waste approach to the management of kitchen waste.