Zheng, 62, headed the watchdog State Food and Drug Administration which sets standards for food and drug safety, from 1998 until he was sacked in 2005.
Beijing has pledged tougher inspections amid growing domestic and international alarm over tainted products. Several countries have already imposed bans or voiced concerns about Chinese imports:
Deaths of hundreds of pets blamed on Chinese pet food tainted with melamine, a chemical used in plastics, fertilisers and fireproofing
Mississippi and Alabama banned Chinese catfish after tests found they contained antibiotics
Europe and Japan
Excessive antibiotic or pesticide residues in Chinese shrimp, honey and other products
Turbot found to contain traces of malachite green - a potential cancer-causing chemical used to treat fungal infections
Babies die after being fed fake baby formula
Cancer-causing dyes injected into eggs to make yolks redder
Children given saltwater passed off as rabies vaccine
He was expelled from the ruling Communist party this year after investigators said he abused the administration's approval powers to obtain bribes and illegal profits from drug companies.
Zheng's powers increased substantially in 2002 when the government required all drugs be approved by the agency.
The change resulted in a massive backlog, giving companies a strong incentive to find ways to speed up approvals.
During his trial Zheng was accused of taking up to $780,000 in bribes to approve untested medicines, including an antibiotic that killed at least 10 patients.
His unusually harsh sentence may yet be reduced on appeal.
The last time China sentenced an official of Zheng's rank to death was in 2000, when Hu Changqing, a vice-governor of the eastern Jiangxi province, and Cheng Kejie, a vice-head of the National People's Congress, were executed for taking bribes.
In another case, local media reported that families of Chinese patients killed by a fake medical ingredient maker linked to widespread deaths in Panama have sued the southern Chinese hospital that administered the toxic injections.
They are seeking 20 million yuan ($2.6m) in compensation.
"These incidents have exposed serious problems in the production and distribution of medicines," the Information Times quoted one of the plaintiffs' lawyers as saying in the hearing that began on Monday.
Beijing has promised to subject food and
drugs to tougher inspections [GALLO/GETTY]
Beijing has promised to subject all food and drugs to more rigorous inspections amid fears that tainted food scandals could lead to bans on Chinese food products.
Announcing new measures to tackle the problem on Tuesday, the govermment said it would be introducing a food recall system that will focus on "potentially dangerous and unapproved food products," the state-run China Daily newspaper said.
Earlier this month authorities announced the detention of managers from two Chinese firms linked to contaminated pet food sold in the US.
Ingredients used in the pet food had reportedly been tainted with melamine, a chemical used in plastics, fertilisers and flame retardants.
And in recent days the US government has stopped all imports of Chinese toothpaste after reports that some products sold in Australia, the Dominican Republic and Panama were tainted with diethylene glycol, a chemical commonly used in antifreeze and brake fluid.